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Transcriptional responses of Rosa rugosa to salt stress and salt shock

Respostas transcricionais de Rosa rugosa ao estresse e choque salino

ABSTRACT

Rugosa rugosa has high tolerance to various stresses; however, the molecular mechanisms of this behavior under adverse conditions are unclear. The objective of this study is to investigate expression patterns of stress-related genes in response to salinity stress. Changes in transcript levels of R. rugose, grown under different salt stress conditions (0, 25, 50, and 100 mM NaCl) over a long exposure period (30 days), have been investigated. In addition, the effects of salt shock stress on seedlings exposed to a high level (200 mM) of NaCl for a relatively short duration (3 h) have also been investigated. Expression levels of selected differentially expressed genes have been determined using relative reverse transcription polymerase chain reaction (RT-PCR). It has been observed that seedlings exposed to salt stress for a long duration exhibited no signs of stress in both leaves and roots. In addition, expression of NHX1 in R. rugosa increased in the presence of NaCl. Furthermore, transcripts of EXP4, GPP, NHX1, NAC, and DREB genes also increased under high levels of NaCl. In contrast, expression levels of MYB and TIR decreased during this salt shock treatment. Of particular interest is the increase in levels of transcripts of NHX1 in leaves of seedlings grown under both salt stress and salt shock conditions, thus suggesting that this gene plays an important role in salt stress tolerance in R. rugosa. These findings will support efforts in enhancing salt tolerance in roses, and perhaps in other members of the Rosaceae family.

Index terms:
Rosaceae; salinity; salt tolerance; ion homeostasis

RESUMO

Rugosa rugosa tem alta tolerância a várias estresses; no entanto, os mecanismos moleculares dessa aptidão sob condições adversas não são claros. O objetivo deste estudo é investigar padrões de expressão de genes relacionados ao estresse em resposta a salinidade. Alterações nos níveis de transcrição de mudas de R. rugosa, cultivadas sob diferentes condições de estresse salino (0, 25, 50 e 100 mM de NaCl) durante um longo período de exposição (30 dias), foram investigadas. Além disso, os efeitos do estresse por choque salino após a exposição das mudas a um nível alto (200 mM) de NaCl por um período relativamente curto (3 h) também foram investigados. Os níveis de expressão de genes expressos diferencialmente selecionados foram determinados usando a reação em cadeia da polimerase com transcrição reversa relativa (RT-PCR). Observou-se que as mudas expostas ao estresse salino por um longo período não apresentaram sinais de estresse nas folhas e nas raízes. Além disso, a expressão de NHX1 em R. rugosa aumentou na presença de NaCl. Além disso, os transcritos dos genes EXP4, GPP, NHX1, NAC e DREB também aumentaram em mudas cultivadas sob altos níveis de NaCl. Em contraste, os níveis de expressão de MYB e TIR diminuíram durante o tratamento com choque salino. De particular interesse é o aumento nos níveis de transcritos do NHX1 nas folhas de mudas cultivadas sob estresse e choque salino, sugerindo que esse gene desempenhe um papel importante na tolerância ao estresse salino em R. rugosa. Essas descobertas apoiarão os esforços para melhorar a tolerância ao sal nas rosas e, talvez, em outros membros da família Rosaceae.

Termos para indexação:
Rosaceae; salinidade; tolerância; íon homeostase

INTRODUCTION

Rosa rugosa Thumb., commonly known as rugosa rose or Japanese rose, is native to East Asia (Bruun, 2005BRUUN, H. H. Rosa rugosa thunb. Ex Murray. Journal of Ecology, 93(2):441-470, 2005.). It is an important species for ornamental use in gardens, fragrance extraction, medicinal and food purposes, as well as a source of several valuable biological metabolites (Na et al., 2016NA, J. et al. Antistress effects of Rosa rugosa Thunb. on total sleep deprivation-induced anxiety-like behavior and cognitive dysfunction in rat: Possible mechanism of action of 5-HT 6 receptor antagonist. Journal of Medicinal Food, 19(9):870-81, 2016.; Olech; Nowak, 2012OLECH, M.; NOWAK, R. Influence of different extraction procedures on the antiradical activity and phenolic profile of rosa rugosa petals. Acta Poloniae Pharmaceutica, 69(3):501-507, 2012.; Ren et al., 2018REN, G. et al. Determination of the volatile and polyphenol constituents and the antimicrobial, antioxidant, and tyrosinase inhibitory activities of the bioactive compounds from the by-product of Rosa rugosa Thunb. var. Plena regal tea. BMC Complementary and Alternative Medicine, 18(1):307, 2018. ; Xie; Zhang, 2012XIE, Y.; ZHANG, W. Antihypertensive ctivity of Rosa rugosa Thunb. flowers: Angiotensin I converting enzyme inhibitor. Journal of Ethnopharmacology, 144(3):562-566, 2012.; Zhang et al., 2019ZHANG, C. et al. Purification, characterization, antioxidant and moisture-preserving activities of polysaccharides from Rosa rugosa petals. International Journal of Biological Macromolecules, 124:938-945, 2019. ). Japanese rose is a salt-tolerant genotype capable of growing in naturally occurring sand dunes. Furthermore, Japanese rose grow most often on either sandy or gravel soils, but occasionally on other well-drained substrates, forming natural communities in sand dunes, shingle beaches, and on sea cliffs (Bruun, 2006BRUUN, H. H. Prospects for biocontrol of invasive rosa rugosa. Biocontrol, 51:141-181, 2006.). In European coastal areas, R. rugosa has been introduced for sand stabilization and for creating pathway boundaries, and it has also been used for ornamental purposes (Bruun, 2006BRUUN, H. H. Prospects for biocontrol of invasive rosa rugosa. Biocontrol, 51:141-181, 2006.; Hill et al., 2010HILL, N. et al. Rosa rugosa as an invader of coastal sand dunes of cape breton island and mainland of Nova Scotia. Canadian Field-Naturalist, 124(2):151-158, 2010.). Interestingly, this species is considered as an invasive plant that is difficult to control in northern Europe due to its high competitiveness (Kelager; Pedersen; Bruun, 2013KELAGER, A.; PEDERSEN J. S.; BRUUN, H. H. Multiple introductions and no loss of genetic diversity: Invasion history of japanese rose, rosa rugosa, in Europe. Biological Invasions, 15(5):1125-1141, 2013.; Stefanowicz et al., 2019STEFANOWICZ, A. M. et al. Invasion of Rosa rugosa Induced changes in soil nutrients and microbial communities of coastal sand dunes. Science of the Total Environment, 677: 340-349, 2019.).

Wild-type R. rugosa has a higher level of resistance to salt stress than its cultivated forms, such as ‘Ziyan’, ‘Purple Branch’, and ‘Zhongke 2’ (Yang; Zhao; Xu, 2011YANG, Z. Y.; ZHAO, L. Y.; XU, Z. D. Impacts of salt stress on the growth and physiological characteristics of Rosa rugosa. Journal of Applied Ecology, 22(8):1993-1998, 2011.). When treated daily with 0.25 N NaCl, plants demonstrated no injuries, and had the lowest Na and Cl contents in their leaves (Dirr, 1978DIRR, M. A. Tolerance of seven woody ornamentals to soil-applied sodium chloride. Journal Arboriculture, 4(7):162-165,1978.). However, the mechanism underlying this observed salt stress tolerance in Japanese rose remains unclear. Gaining knowledge of the mechanism(s) of salt tolerance in plants is important for developing alternative solutions for salinity problems in agricultural crops (Reis et al., 2016REIS, M. V. et al. Salinity in rose production. Ornamental Horticulture, 22(2):228-234, 2016.; Bechtold; Field, 2018BECHTOLD, U.; FIELD, B. Molecular mechanisms controlling plant growth during abiotic stress, Journal of Experimental Botany, 69(11):2753-2758, 2018.; Byrt et al., 2018BYRT, C. S. et al. Root cell wall solutions for crop plants in saline soils. Plant Science, 269:47-55, 2018.; Figueiredo et al., 2017FIGUEIREDO, J. R. M. et al. Development changes in calla lily plants due to salt stress. Acta Physiology Plantarum, 39:147, 2017.; Barros; Melo; Souza, 2019BARROS, C. V. S. D.; MELO, Y. L.; SOUZA, M. D. F. Sensitivity and biochemical mechanisms of sunflower genotypes exposed to saline and water stress. Acta Physiology Plantarum, 41:159, 2019.). Thus, the goal of this study is to investigate the molecular mechanism(s) of salt tolerance in R. rugosa salt tolerance by evaluating the effects of long exposure of young seedlings of R. rugosa to salinity stress and to salt shock on transcription profiles of a select stress-related genes.

MATERIAL AND METHODS

Plant material and growth conditions

Seeds of R. rugosa were stored in plastic bags containing sphagnum moss at 4 °C, for a period of ~3 months for stratification, until germination. Subsequently, germinating seedlings were transferred to 15 cm (diameter) plastic pots containing Sunshine Mix, moved to the greenhouse, and grown under conditions of 25 °C / 18 °C, day/night temperature, and 16 h of daylight.

Salinity stress treatment

To evaluate the effects of long exposure to salt stress, three-month-old seedlings were irrigated with a solution of either 0, 25, 50, or 100 mM NaCl once every two days for a period of 30 days. A total of three plants (biological replicates) per treatment were used, and these were arranged in a completely randomized design. At the end of the experiment, leaves from the second nodes were collected, immediately frozen in liquid nitrogen, and then stored at -80 °C until use.

For evaluation of salt shock, six-month-old plants, growing in the greenhouse, were irrigated with either 200 mM NaCl or water (control). Three plants (biological replicates) per treatment were used, and these were arranged in a completely randomized design. After 3 h of treatment, leaves from the second nodes were collected, immediately frozen in liquid nitrogen, and stored at -80 °C until use.

RNA extraction and cDNA synthesis

Leaf tissues were removed from the ultrafreezer, 10% polyvinylpyrrolidone was added, and then these tissues were ground into a fine powder. Total RNA was extracted from these ground leaf tissues using an RNase Plant Minikit (Qiagen, Doncaster, VIC, Australia), but with modifications. RNA was quantified using a NanoDrop ND-100 spectrophotometer (NanoDrop Technologies, Wilmington, DE). Total RNA from each sample was treated with DNase I (Invitrogen), and then used for cDNA synthesis. First-strand cDNA synthesis was performed with an Oligo (dt) primer using SuperScript III RT (Invitrogen).

Quantitative Real-time PCR for expression analysis

cDNA was diluted to 30 ng/µl, and used for real-time PCR in 96-well plates in a 7300 real-time PCR system (Applied Biosystems, Foster City, CA). Real-time quantitative reverse transcription (qRT)- PCR was performed on three independent biological replicates, each containing three technical replicates, using a SYBR Green PCR Master Mix (Applied Biosystems). Gene-specific primers from select stress-related genes, identified for real-time RT-PCR, were designed using the Primer 3 program (UNTERGASSER et al., 2012UNTERGASSER, A. et al. Primer3: New capabilities and interfaces, Nucleic Acids Research, 4(15), e115, 2012.) based on BLAST consensus sequences from GenBank. Each reaction (25 µl) contained 10.5 µl water, 0.5 µl of 200 nM forward and reverse primers, 12.5 µl of 2 x SYBR Green I Master, and 5 µl diluted cDNA. The amplification program consisted of one cycle of 95 °C for 10 min followed by 95 °C for 15 s and 60 °C for 1 min. Following amplification, a melting curve analysis was run using the program for one cycle at 95 °C for 5 s, 65 °C for 1 min, and 95 °C with a hold of 0 s in the acquisition step mode, followed by cooling at 4 °C for 10 s. A negative control without a cDNA template was run with each analysis to evaluate the overall specificity. To normalize the total amount of cDNA in each reaction, select rose genes were co-amplified, as internal controls, using RhGADPH (EC589884) from R. hybrida (hybrid tea rose).

Data were analyzed using SDS software from a 7300 Real-time PCR system (Applied Biosystems) based on relative standard curves of PCR efficiency of target and reference genes.

For the long duration salt stress exposure experiment, expression of the following stress-related genes, RhNAC, RhNHX1, and RhEPX4, were investigated. Whereas, for the salt shock experiment, expression of the following stress-related genes, RhNAC, RhNHX, RhEPX4, RrGPP, RhDREB1B, RrMYB, and RhTIR, were investigated.

RESULTS AND DISCUSSION

Long-term exposure to NaCl

Rosa rugosa originally grew in sand dunes. In the European coastal area, R. rugosa was planted for sand stabilization for pathway boundaries, and for use as an ornamental plant (Kelager; Pedersen; Bruun, 2013KELAGER, A.; PEDERSEN J. S.; BRUUN, H. H. Multiple introductions and no loss of genetic diversity: Invasion history of japanese rose, rosa rugosa, in Europe. Biological Invasions, 15(5):1125-1141, 2013.). As high soil salinity can occur naturally or human induced, it is important the introduction of good agricultural practices associated with the use of genotypes that are more tolerant to salinity soil conditions to alleviate salt stress problems. In fact, salt tolerant plant are well-adapted to such soil conditions, and their fitness enables them to re-establish osmotic and ionic homeostasis in response to salinity stress. It is these responses that will maintain the physiological and biochemical activities that will support plant growth under such stress environmental conditions.

In this study, the effects of salt stress on R. rugosa seedlings were investigated in order to develop a better understanding of the mechanism of salt stress on this plant. R. rugosa subjected to high salinity, for a relatively long exposure period of 30 days, were investigated. It was observed that none of the plants treated with different concentrations of NaCl showed signs of stress (Figure 1A and 1B). These results indicated that R, rugosa seedlings were indeed salt-tolerant to these varying levels of NaCl. These findings were similar to observations reported in other rose genotypes subjected to different levels of salt stress (Niu; Rodriguez; Aguiniga, 2008NIU, G.; RODRIGUEZ, D. S.; AGUINIGA, L. Effect of saline water irrigation on growth and physiological responses of three rose rootstocks. HortScience, 43(5):1479-1484, 2008.).

It is known that salt stress tolerance is related to expression of stress-related genes in plants (Dai et al., 2012DAI, F. et al. RhNAC2 and RhEXPA4 are involved in the regulation of dehydration tolerance during the expansion of rose petals. Plant Physiology, 160(4):2064-2082, 2012. ; Wang et al., 2016WANG, H. et al. Recent advances in utilizing transcription factors to improve plant abiotic stress tolerance by transgenic technology. Frontiers in Plant Science , 7:67, 2016.; Razzaque et al., 2019RAZZAQUE, S. et al. Gene expression analysis associated with salt stress in a reciprocally crossed rice population. Scientific reports, 9:8249, 2019.). To study the molecular mechanism(s) of salt stress tolerance in R. rugosa, qRT-PCR analysis of select stress-related genes, including NAC, NHX1, and EXP4, has been conducted to identify patterns of gene expression in seedlings subjected to salt stress. It is found that transcript levels of NAC are significantly higher in young plants treated with NaCl compared to those of control (Figure 1C). Among the three NaCl treatments, NAC transcripts are higher in plants grown under 100 mM NaCl, these are not significantly different from those grown under 25 mM or 50 mM (Figure 1C). NAC proteins are involved in different biological plant events, such as development, as well as biotic and abiotic stress responses (Wang; Dane, 2013WANG, Z.; DANE, F. NAC (NAM/ATAF/CUC) transcription factors in different stresses and their signaling pathway. Acta Physiologiae Plantarum, 35(5):1397-1408, 2013.) Tobacco plants overexpressing DgNAC1 (Dendranthema grandiflorum NAC) have exhibited a markedly increased tolerance to salt (Liu et al., 2011LIU, Q. et al. Overexpression of a novel chrysanthemum nac transcription factor gene enhances salt tolerance in tobacco. Biotechnology Letters, 33(10):2073-2082, 2011.). In this study, the observed high levels of expression of NACgenes under NaCl treatments suggest that NAC transcription factors play important roles in salt stress tolerance and adaptation of rugosa rose.

Expression of NHX1 increased significantly in R. rugosa young plants growning under salt stress conditions compared to those grown under control treatment (Figure 1C). Furthermore, NHX1 transcripts in plants treated with 25 mM NaCl were 4-fold higher than that those detected in control seedlings. Moreover, NHX1 transcripts in R. rugosa subjected to 50 and 100 mM NaCl were approximantely 16-fold higher than those of control seedlings, respectively. These findings indicated that plants treated with higher concentrations of NaCl significantly increased expression levels of NHX1 compared to those of control plants. Previously, it has been reported that a vacuolar Na+/H+ antiporter gene in R. hybrida, RhNHX1, demonstrated an increase in expression in the presence of NaCl (Kagami; Suzuki, 2005KAGAMI, T.; SUZUKI, M. Molecular and functional analysis of a vacuolar Na+/H+ antiporter gene of Rosa hybrida. Genes & Genetic Systems, 80(2):121-128, 2005.).

The Na+/H antiporter is a transmembrane transport protein that excludes Na+ from the cytosol in exchange for H+ intracellular Na+/H+. NHX proteins are well-known plant cation/proton antiporters that are involved in Na+and K+compartmentalization into the vacuole, and play an important role in maintaining cellular pH, Na+ (compartmentalization), and K+(homeostasis) levels (Bassil et al., 2011BASSIL, E. et al. The arabidopsis Na+/H+ antiporters NHX1 and NHX2 control vacuolar PH and K+ homeostasis to regulate growth, flower development, and reproduction. The Plant Cell, 23(9):3482-3497, 2011. ; Pires et al., 2013PIRES, I. S. et al. Different evolutionary histories of two cation/proton exchanger gene families in plants. BMC Plant Biology , 13:97, 2013. ). NHX is a salt tolerance determinant. This protein promotes ion homeostasis in saline environments. AtNHX proteins in Arabidopsis facilitate Na+ion compartmentalization and maintain the intracellular K+ status. It has been reported that overexpression of NHX1 in rice, Arabidopsis, cumin, mungbean and soybean is correlated with salt tolerance in these plant species (Liu et al., 2010LIU, H. et al. AtNHX3 Is a vacuolar K+/H+ antiporter required for low-potassium tolerance in Arabidopsis thaliana. Plant, Cell and Environment, 33(11):1989-1999, 2010. ; Kumar et al., 2017KUMAR, S. et al. Co-expression of arabidopsis NHX1 and bar improves the tolerance to salinity, oxidative stress, and herbicide in transgenic mungbean. Frontiers in Plant Science , 8:1896, 2017.).

In earlier studies, it has been observed that the sodium concentration in the medium positively correlates with the sodium absorption in roses (Lorenzo et al., 2000LORENZO, H. et al. Effects of sodium on mineral nutrition in rose plants. Annals of Applied Biology, 137(1):65-72, 2000.; Massa; Mattson; Lieth, 2008MASSA, D.; MATTSON, N. S.; LIETH, H. J. Effects of saline root environment (NACl) on nitrate and potassium uptake kinetics for rose plants: A Michaelis-Menten modelling approach. Plant and Soil, 318(1-2):101-115, 2008. ). Sodium is reported to play an important role in the stimulation of electrical conductivity (Ec) in environments in which a high salinity level (NaCl) occurs in the irrigation water source. As the sodium concentration increases, can promote an ion imbalance, especially of potassium (K) (Almeida; Oliveira; Saibo, 2017ALMEIDA, D. M.; OLIVEIRA, M. M.; SAIBO, N. J. M. Regulation of Na+ and K+ homeostasis in plants: Towards improved salt stress tolerance in crop plants. Genetics and Molecular Biology, 40(1):326-345, 2017.). Chrysanthemum morifolium ‘Jinba’ is less salt tolerant specie, that under salinity stress, showed lower K+/Na+ ratio (Gao et al., 2016GAO, J. et al. Variation in tissue Na+ content and the activity of SOS1 genes among two species and two related genera of chrysanthemum. BMC Plant Biology, 16:98, 2016.).

In this study, expression levels of EXP4 significantly increased when rugosa seedlings were treated with NaCl compared to control treatment (Figure 1C). This suggested that the expansin gene in rugosa rose was highly expressed in response to salt stress treatments, and played similar roles to NAC transcription factors and NHX1 protein family in supporting plant growth and development under these salt stress conditions. Previously, it has been suggested that RhEXPA4 of R. hybrida conferred tolerance to abiotic stresses in Arabidopsis by modifying cell expansion and plant development (Lu et al., 2013LU, P. et al. RhEXPA4, a rose expansin gene, modulates leaf growth and confers drought and salt tolerance to arabidopsis. Planta , 237(6):1547-1559, 2013.). Additionally, RhEXPA4was involved in the regulation of dehydration tolerance during rose petal expansion (Dai et al., 2012DAI, F. et al. RhNAC2 and RhEXPA4 are involved in the regulation of dehydration tolerance during the expansion of rose petals. Plant Physiology, 160(4):2064-2082, 2012. ). Although, three other forms of expansins have been identified in R. hybrida, including RhEXP 1, 2, and 3 have been identified, RhEXP1 was reported to be involved in the expansion growth of rose petals (Takahashi et al., 2007TAKAHASHI, R. et al. Analysis of the cell wall loosening proteins during rose flower opening. Acta Horticulturae, 755:483-88, 2007.). Expansin genes have been reported to be active in cell walls (CWs), contributing their loosening and extension (Abuqamar et al., 2013ABUQAMAR, S. et al. A mutation in the expansin-like a2 gene enhances resistance to necrotrophic fungi and hypersensitivity to abiotic stress in arabidopsis thaliana. Molecular Plant Pathology, 14(8):813-827, 2013. ). However, this group of genes have been observed to respond to different biotic and abiotic stresses, wherein cell wall-modifying proteins were reported to mediate plant acclimatization to biotic and abiotic stresses (Sasidharan; Voesenek; Pierik, 2011SASIDHARAN, R.; VOESENEK, L. A. C. J.; PIERIK, R. Cell wall modifying proteins mediate plant acclimatization to biotic and abiotic stresses. Critical Reviews in Plant Sciences, 30(6):548-562, 2011.; Chen et al., 2018CHEN, L. et al. Tobacco alpha-expansin EXPA4 plays a role in Nicotiana benthamiana defence against Tobacco mosaic virus. Planta, 247(8):355-368, 2018.). For example, Arabidopsis  expansin-like A2 ( EXLA2 ) has been identified to be involved in response to various biotic (necrotrophic pathogenesis) and abiotic (salt, cold, and abscisic acid [ABA]) stresses, while a mutant, exla2 Arabidopsis, was found to be more sensitive to stress (Abuqamar et al., 2013). Therefore, these earlier studies supported our finding in this study that expansins must have significantly contributed to rugosa rose seedlings responses to salt stress, and could be involved in signaling pathways regulating gene expression.

Figure 1:
R. rugosa treated with various levels of NaCl for a period of 30 days. Shoot (A) and root system (B). Relative quantification of gene expression in plants treated with different concentrations of NaCl (0, 25, 50, and 100 mM).

To ensure a plant’s ability in tolerating and/or adapting to salinity, stress tolerance and adaptation mechanisms, such as Na+ vacuole compartmentalization, are very important, as this adaptation enables a plant to continue growing under conditions of salinity stress. When plants are exposed to salt, they would need to coordinate the expression of several genes to maintain Na+ homeostasis.

Salt shock

Salt shock is an extreme form of salt stress following exposure to a high salt concentration by a single application of salt. As irrigation water may sometimes carry high levels of salt or excess fertilizer is used, it is very important to plant genotypes that can tolerate such stress conditions. In this study, a comparative experiment was conducted to evaluate salt shock treatment response of rugosa rose to 200 mM NaCl treatment for a period of 3h. This particular salt treatment and duration were selected as these conditions have been deemed the most responsive to stress. It has been reported that as sudden exposure to such levels of salt would induce osmotic shock, and deemed as the primary phase of stress (Shavrukov, 2013SHAVRUKOV, Y. Salt stress or salt shock: Which genes are we studying? Journal of Experimental Botany , 64(1):119-127, 2013.). Furthermore, under these conditions, plants would require a strong osmotic adjustment to survive the effects of such salt shock. Moreover, it has been reported that a second phase in this response is related to a gradual increase in ionic components (Shavrukov, 2013). Generally, plants would induce expression of different groups of genes in response to stress, including the following: 1) signal transduction (including genes encoding transcription factors), 2) enzymes, particularly those that respond to plant oxidation stress, 3) osmoprotectants, and 4) proteins related to water stress. Thus, in this study, a group of genes that would respond during salt shock, including expansins, phosphatases, and various other transcription factors (TFs), have been investigated.

Following a 3 h exposure to a salt shock treatment, rugosa rose demonstrated a two-fold increase in levels of EXPA4 gene expression, an expansin gene that responds to osmotic shock and plays a role in salt tolerance, than those grown under control conditions (Figure 2). It has been reported that β-expansin protein levels are found to higher in salt-resistant maize cultivars than in salt-sensitive cultivars (Geilfus et al., 2011GEILFUS, C. M. et al. Differential transcript expression of wall-loosening candidates in leaves of maize cultivars differing in salt resistance. Journal of Plant Growth Regulation , 30(4):387-395, 2011.). Furthermore, β-expansin transcript abundance is reported to be induced inSorghum bicolor and Solanum tuberosum grown under salt and other stress (Buchanan et al., 2005BUCHANAN, C. D. et al. Sorghum Bicolor’s transcriptome response to dehydration, high salinity and ABA. Plant Molecular Biology, 58(5):699-720, 2005.; Chen et al., 2019CHEN, Y. et al. A comprehensive expression analysis of the expansin gene family in potato (Solanum tuberosum) discloses stress-responsive expansin-like B genes for drought and heat tolerances. PLoS One, 14(7):e0219837, 2019.).

Figure 2:
Relative quantification of gene expression in R. rugosa leaves during 3 h of salt shock stress using qRT-PCR analysis.

Transcript abundance analysis of the gene encoding for galactose-1-phosphate phosphatase (GPP) showed a small increase in transcript levels following 3 h of salt shock (Figure 2). Previously, it has been reported that expression of some genes in response to osmotic shock can be registered within minutes of salt shock treatment (Shavrukov, 2013SHAVRUKOV, Y. Salt stress or salt shock: Which genes are we studying? Journal of Experimental Botany , 64(1):119-127, 2013.). Therefore, using a 3 h treatment in this study could have been rather long period of stress, and therefore, expression levels of GPP could have increased and then dropped down to normal levels. It is reported that GPP plays a central role in ABA biosynthesis in higher plants, as ABA is one of the most important and abundantly occurring water-soluble antioxidants in plants (Shavrukov, 2013SHAVRUKOV, Y. Salt stress or salt shock: Which genes are we studying? Journal of Experimental Botany , 64(1):119-127, 2013.). A few studies have demonstrated that exogenous applications of salicylic acid either via the rooting medium or via foliar sprays can alleviate salt stress (Arafa; Khafagy, 2009ARAFA, A. A.; KHAFAGY, M. A. The effect of glycinebetaine or ascorbic acid on grain germination and leaf structure of sorghum plants grown under salinity stress. Australian Journal of Crop Science, 3(5):294-304, 2009.; Shalata; Neumann 2001SHALATA, A.; NEUMANN, P. M. Exogenous ascorbic acid (Vitamin C) increases resistance to salt stress and reduces lipid peroxidation. Journal of Experimental Botany , 52(364):2207-2211, 2001.). In addition, Arabidopsis mutants (ascorbate-deficient) are reported to more sensitive to salinity stress (Huang et al., 2005HUANG, C. et al. Increased sensitivity to salt stress in an ascorbate-deficient arabidopsis mutant. Journal of Experimental Botany , 56(422):3041-3049, 2005.).

In this study, the NAC TF is found to be rapidly induced by salt shock stress treatment, as mRNA levels of RhNAC (R. hybrida NAC) are found to increase after 3 h of this treatment (Figure 2). It has been previously reported that NAC is a stress-responsive TF, and the gene ENAC1,  encoding early NAC - domain protein induced by abiotic stress 1 , has also been found to accumulate in the first hours following exposure to salt shock stress (Sun et al., 2012SUN, H. et al. ENAC1, a NAC transcription factor, is an early and transient response regulator induced by abiotic stress in rice (Oryza sativa L.). Molecular Biotechnology , 52(2):101-110, 2012.).

In this study, it is observed that NHX1 demonstrated high levels of expression in rugosa rose treated with high concentrations of salt (salt shock) (Figure 2). It is reported that Na+/H+ antiporters play important roles in compartmentalization of cytoplasmic Na+ into vacuoles, and thereby their levels of expression increase in the presence of NaCl (Kagami; Suzuki, 2005KAGAMI, T.; SUZUKI, M. Molecular and functional analysis of a vacuolar Na+/H+ antiporter gene of Rosa hybrida. Genes & Genetic Systems, 80(2):121-128, 2005.). Therefore, findings in this study suggest that vacuolar Na+/H+ antiporters are also involved in salt tolerance in rugosa rose, and they do play an important role during the first few hours of salt shock. Previously, it has been reported that AtNHX1and  AtNHX2 expression in Arabidopsis increase in response to high salt stress through an ABA-dependent process. Additionally, theseArabidopsis  Na+/H+antiporters, NHX1 and NHX2, do in fact control vacuolar pH and K+homeostasis to regulate growth, flower development, and reproduction (Bassil et al., 2011BASSIL, E. et al. The arabidopsis Na+/H+ antiporters NHX1 and NHX2 control vacuolar PH and K+ homeostasis to regulate growth, flower development, and reproduction. The Plant Cell, 23(9):3482-3497, 2011. ). In other studies, it has been found that treatments with high concentrations of NaCl and KCl contribute to increases in transcript levels ofNHX1 in roots and shoots (Mahasal; Chaopaknam; Ngampanya, 2011MAHASAL, K.; CHAOPAKNAM, A.; NGAMPANYA, B. Expression analysis of Na+/H+ exchanger and monosaccharide transporter genes in rice suspension cells under salt stress. Thai Journal of Agricultural Science, 44(5):125-128, 2011. , Kumar et al., 2017KUMAR, S. et al. Co-expression of arabidopsis NHX1 and bar improves the tolerance to salinity, oxidative stress, and herbicide in transgenic mungbean. Frontiers in Plant Science , 8:1896, 2017.).

When investigating yet another gene encoding for the DREB1 TF, it has been found that transcript levels of DREB1 have increased in rugosa rose flollowing salt shock treatment (Figure 2). DREB1 is an important TF that regulates various abiotic stress-responsive genes by activation of various downstream regulatory genes. Previous studies have demonstrated that LlaDREB1b, in the perennial herb Lepidium latifolium,is induced by salt and drought stresses, and it is functional in an ABA-independent pathway (Gupta et al., 2013GUPTA, S. M. et al. DRE-binding transcription factor gene (LlaDREB1b) is regulated by various abiotic stresses in Lepidium latifolium L. Molecular Biology Reports, 40(3): 2573-2580, 2013.). Furthermore, overexpression ofStDREB1 of potato increases salt tolerance in transgenic potato plants (Bouaziz et al., 2013BOUAZIZ, D. et al. Overexpression of StDREB1 transcription factor increases tolerance to salt in transgenic potato plants. Molecular Biotechnology, 54(3):803-817, 2013.). In addition, Arabidopsis plants overexpressing MsDREB2, isolated from Malus siverseii, have been found to be more tolerant to salt stress and to other abiotic stresses, including cold, heat, drought, and ABA (Zhao et al., 2013ZHAO, K. et al. Isolation and characterization of dehydration-responsive element-binding factor 2C (MsDREB2C) from Malus sieversii Roem. Plant and Cell Physiology, 54(9): 1415-1430, 2013.). Interestingly, these transgenic Arabidopsis plants have exhibited smaller stomatal apertures, reduced water loss, and higher levels of proline, thereby contributing to increased root growth and shoot growth (Zhao et al., 2013ZHAO, K. et al. Isolation and characterization of dehydration-responsive element-binding factor 2C (MsDREB2C) from Malus sieversii Roem. Plant and Cell Physiology, 54(9): 1415-1430, 2013.).

In this study, salt shock treatment on rugosa rose seedlings induced a drop in expression levels of the brp6 gene encoding for a putative for the TIR-NBS-LRR resistance protein (Figure 2). This finding is similar to earlier reports wherein this gene is found to be downregulated in response to both drought and short-term salinity stress in Thellungiella halophila, a close relative halophyte of Arabidopsis, although it is upregulated over a long-period of stress (Gao et al., 2008GAO, F. et al. Proteomic analysis of long-term salinity stress-responsive proteins in Thellungiella halophila leaves. Chinese Science Bulletin, 53(22):3530-3537, 2008. ). It is known that these genes are involved in various biotic and abiotic stresses, thus demonstrating the complex mechanism of stress response adaptation in plants (Wang et al., 2016WANG, H. et al. Recent advances in utilizing transcription factors to improve plant abiotic stress tolerance by transgenic technology. Frontiers in Plant Science , 7:67, 2016.; Banerjee et al., 2019BANERJEE, A. et al. Salt acclimation differentially regulates the metabolites commonly involved in stress tolerance and aroma synthesis in indica rice cultivars. Plant Growth Regulation, 88:87-97, 2019.).

Finally, transcripts of yet another TF investigated in this study, myb9 gene, are found to drop slightly in rugosa rose seedlings subjected to salt shock treatment (Figure 2). The MYB TF factor, as well as other TFs, including AP2/ERF, NAC, bZIP, MYC, WRKY, and Cys2/His2-type zinc finger protein families can activate and repress many functional genes related to stress in response to environmental stresses (Golldack; Lüking; Yang, 2011GOLLDACK, D.; LÜKING, I.; YANG, O. Plant tolerance to drought and salinity: Stress regulating transcription factors and their functional significance in the cellular transcriptional network. Plant Cell Reports, 30(8):1383-1391, 2011.; Shavrukov, 2013SHAVRUKOV, Y. Salt stress or salt shock: Which genes are we studying? Journal of Experimental Botany , 64(1):119-127, 2013.). Therefore, it is likely that myb9 may not play an important role in salt shock response in rugosa rose. Therefore, various other myb genes should be investigated in future studies to determine their potential roles in salinity shock responses in rose.

CONCLUSIONS

In this study, R. rugosa did not exhibit any salt injury symptoms after 30 days of salinity stress or 3 h of salt shock, thus suggesting that rugosa or Japanese rose has high levels of resistance to salinity stress. This observed tolerance of R. rugosa to salt stress may be related to high levels of expression of NHX1 following exposure to long salt stress duration and to salt shock treatments. These findings contribute new knowledge to our understanding of salt stress tolerance in rose plants, and likely to other plants.

ACKNOWLEDGEMENTS

This study was supported in part by research funds provided by the Coordination for the Improvement of Higher Education Personnel (CAPES), the National Council for Scientific and Technological Development (CNPq), and the Research Support Foundation of the states of Minas Gerais (FAPEMIG), all in Brazil. In addition, research funding was also received from the Office of Research of the College of Agricultural, Consumer, and Environmental Sciences at the University of Illinois at Urbana-Champaign.

REFERENCES

  • ABUQAMAR, S. et al. A mutation in the expansin-like a2 gene enhances resistance to necrotrophic fungi and hypersensitivity to abiotic stress in arabidopsis thaliana. Molecular Plant Pathology, 14(8):813-827, 2013.
  • ALMEIDA, D. M.; OLIVEIRA, M. M.; SAIBO, N. J. M. Regulation of Na+ and K+ homeostasis in plants: Towards improved salt stress tolerance in crop plants. Genetics and Molecular Biology, 40(1):326-345, 2017.
  • ARAFA, A. A.; KHAFAGY, M. A. The effect of glycinebetaine or ascorbic acid on grain germination and leaf structure of sorghum plants grown under salinity stress. Australian Journal of Crop Science, 3(5):294-304, 2009.
  • BANERJEE, A. et al. Salt acclimation differentially regulates the metabolites commonly involved in stress tolerance and aroma synthesis in indica rice cultivars. Plant Growth Regulation, 88:87-97, 2019.
  • BARROS, C. V. S. D.; MELO, Y. L.; SOUZA, M. D. F. Sensitivity and biochemical mechanisms of sunflower genotypes exposed to saline and water stress. Acta Physiology Plantarum, 41:159, 2019.
  • BASSIL, E. et al. The arabidopsis Na+/H+ antiporters NHX1 and NHX2 control vacuolar PH and K+ homeostasis to regulate growth, flower development, and reproduction. The Plant Cell, 23(9):3482-3497, 2011.
  • BECHTOLD, U.; FIELD, B. Molecular mechanisms controlling plant growth during abiotic stress, Journal of Experimental Botany, 69(11):2753-2758, 2018.
  • BOUAZIZ, D. et al. Overexpression of StDREB1 transcription factor increases tolerance to salt in transgenic potato plants. Molecular Biotechnology, 54(3):803-817, 2013.
  • BRUUN, H. H. Rosa rugosa thunb. Ex Murray. Journal of Ecology, 93(2):441-470, 2005.
  • BRUUN, H. H. Prospects for biocontrol of invasive rosa rugosa. Biocontrol, 51:141-181, 2006.
  • BUCHANAN, C. D. et al. Sorghum Bicolor’s transcriptome response to dehydration, high salinity and ABA. Plant Molecular Biology, 58(5):699-720, 2005.
  • BYRT, C. S. et al. Root cell wall solutions for crop plants in saline soils. Plant Science, 269:47-55, 2018.
  • CHEN, L. et al. Tobacco alpha-expansin EXPA4 plays a role in Nicotiana benthamiana defence against Tobacco mosaic virus Planta, 247(8):355-368, 2018.
  • CHEN, Y. et al. A comprehensive expression analysis of the expansin gene family in potato (Solanum tuberosum) discloses stress-responsive expansin-like B genes for drought and heat tolerances. PLoS One, 14(7):e0219837, 2019.
  • DAI, F. et al. RhNAC2 and RhEXPA4 are involved in the regulation of dehydration tolerance during the expansion of rose petals. Plant Physiology, 160(4):2064-2082, 2012.
  • DIRR, M. A. Tolerance of seven woody ornamentals to soil-applied sodium chloride. Journal Arboriculture, 4(7):162-165,1978.
  • FIGUEIREDO, J. R. M. et al. Development changes in calla lily plants due to salt stress. Acta Physiology Plantarum, 39:147, 2017.
  • GAO, F. et al. Proteomic analysis of long-term salinity stress-responsive proteins in Thellungiella halophila leaves. Chinese Science Bulletin, 53(22):3530-3537, 2008.
  • GAO, J. et al. Variation in tissue Na+ content and the activity of SOS1 genes among two species and two related genera of chrysanthemum. BMC Plant Biology, 16:98, 2016.
  • GEILFUS, C. M. et al. Differential transcript expression of wall-loosening candidates in leaves of maize cultivars differing in salt resistance. Journal of Plant Growth Regulation , 30(4):387-395, 2011.
  • GOLLDACK, D.; LÜKING, I.; YANG, O. Plant tolerance to drought and salinity: Stress regulating transcription factors and their functional significance in the cellular transcriptional network. Plant Cell Reports, 30(8):1383-1391, 2011.
  • GUPTA, S. M. et al. DRE-binding transcription factor gene (LlaDREB1b) is regulated by various abiotic stresses in Lepidium latifolium L. Molecular Biology Reports, 40(3): 2573-2580, 2013.
  • HILL, N. et al. Rosa rugosa as an invader of coastal sand dunes of cape breton island and mainland of Nova Scotia. Canadian Field-Naturalist, 124(2):151-158, 2010.
  • HUANG, C. et al. Increased sensitivity to salt stress in an ascorbate-deficient arabidopsis mutant. Journal of Experimental Botany , 56(422):3041-3049, 2005.
  • KAGAMI, T.; SUZUKI, M. Molecular and functional analysis of a vacuolar Na+/H+ antiporter gene of Rosa hybrida Genes & Genetic Systems, 80(2):121-128, 2005.
  • KELAGER, A.; PEDERSEN J. S.; BRUUN, H. H. Multiple introductions and no loss of genetic diversity: Invasion history of japanese rose, rosa rugosa, in Europe. Biological Invasions, 15(5):1125-1141, 2013.
  • KUMAR, S. et al. Co-expression of arabidopsis NHX1 and bar improves the tolerance to salinity, oxidative stress, and herbicide in transgenic mungbean. Frontiers in Plant Science , 8:1896, 2017.
  • LIU, H. et al. AtNHX3 Is a vacuolar K+/H+ antiporter required for low-potassium tolerance in Arabidopsis thaliana Plant, Cell and Environment, 33(11):1989-1999, 2010.
  • LIU, Q. et al. Overexpression of a novel chrysanthemum nac transcription factor gene enhances salt tolerance in tobacco. Biotechnology Letters, 33(10):2073-2082, 2011.
  • LORENZO, H. et al. Effects of sodium on mineral nutrition in rose plants. Annals of Applied Biology, 137(1):65-72, 2000.
  • LU, P. et al. RhEXPA4, a rose expansin gene, modulates leaf growth and confers drought and salt tolerance to arabidopsis. Planta , 237(6):1547-1559, 2013.
  • MAHASAL, K.; CHAOPAKNAM, A.; NGAMPANYA, B. Expression analysis of Na+/H+ exchanger and monosaccharide transporter genes in rice suspension cells under salt stress. Thai Journal of Agricultural Science, 44(5):125-128, 2011.
  • MASSA, D.; MATTSON, N. S.; LIETH, H. J. Effects of saline root environment (NACl) on nitrate and potassium uptake kinetics for rose plants: A Michaelis-Menten modelling approach. Plant and Soil, 318(1-2):101-115, 2008.
  • NA, J. et al. Antistress effects of Rosa rugosa Thunb. on total sleep deprivation-induced anxiety-like behavior and cognitive dysfunction in rat: Possible mechanism of action of 5-HT 6 receptor antagonist. Journal of Medicinal Food, 19(9):870-81, 2016.
  • NIU, G.; RODRIGUEZ, D. S.; AGUINIGA, L. Effect of saline water irrigation on growth and physiological responses of three rose rootstocks. HortScience, 43(5):1479-1484, 2008.
  • OLECH, M.; NOWAK, R. Influence of different extraction procedures on the antiradical activity and phenolic profile of rosa rugosa petals. Acta Poloniae Pharmaceutica, 69(3):501-507, 2012.
  • PIRES, I. S. et al. Different evolutionary histories of two cation/proton exchanger gene families in plants. BMC Plant Biology , 13:97, 2013.
  • RAZZAQUE, S. et al. Gene expression analysis associated with salt stress in a reciprocally crossed rice population. Scientific reports, 9:8249, 2019.
  • REIS, M. V. et al. Salinity in rose production. Ornamental Horticulture, 22(2):228-234, 2016.
  • REN, G. et al. Determination of the volatile and polyphenol constituents and the antimicrobial, antioxidant, and tyrosinase inhibitory activities of the bioactive compounds from the by-product of Rosa rugosa Thunb. var. Plena regal tea. BMC Complementary and Alternative Medicine, 18(1):307, 2018.
  • SASIDHARAN, R.; VOESENEK, L. A. C. J.; PIERIK, R. Cell wall modifying proteins mediate plant acclimatization to biotic and abiotic stresses. Critical Reviews in Plant Sciences, 30(6):548-562, 2011.
  • SHALATA, A.; NEUMANN, P. M. Exogenous ascorbic acid (Vitamin C) increases resistance to salt stress and reduces lipid peroxidation. Journal of Experimental Botany , 52(364):2207-2211, 2001.
  • SHAVRUKOV, Y. Salt stress or salt shock: Which genes are we studying? Journal of Experimental Botany , 64(1):119-127, 2013.
  • STEFANOWICZ, A. M. et al. Invasion of Rosa rugosa Induced changes in soil nutrients and microbial communities of coastal sand dunes. Science of the Total Environment, 677: 340-349, 2019.
  • SUN, H. et al. ENAC1, a NAC transcription factor, is an early and transient response regulator induced by abiotic stress in rice (Oryza sativa L.). Molecular Biotechnology , 52(2):101-110, 2012.
  • TAKAHASHI, R. et al. Analysis of the cell wall loosening proteins during rose flower opening. Acta Horticulturae, 755:483-88, 2007.
  • UNTERGASSER, A. et al. Primer3: New capabilities and interfaces, Nucleic Acids Research, 4(15), e115, 2012.
  • WANG, Z.; DANE, F. NAC (NAM/ATAF/CUC) transcription factors in different stresses and their signaling pathway. Acta Physiologiae Plantarum, 35(5):1397-1408, 2013.
  • WANG, H. et al. Recent advances in utilizing transcription factors to improve plant abiotic stress tolerance by transgenic technology. Frontiers in Plant Science , 7:67, 2016.
  • XIE, Y.; ZHANG, W. Antihypertensive ctivity of Rosa rugosa Thunb. flowers: Angiotensin I converting enzyme inhibitor. Journal of Ethnopharmacology, 144(3):562-566, 2012.
  • YANG, Z. Y.; ZHAO, L. Y.; XU, Z. D. Impacts of salt stress on the growth and physiological characteristics of Rosa rugosa Journal of Applied Ecology, 22(8):1993-1998, 2011.
  • ZHANG, C. et al. Purification, characterization, antioxidant and moisture-preserving activities of polysaccharides from Rosa rugosa petals. International Journal of Biological Macromolecules, 124:938-945, 2019.
  • ZHAO, K. et al. Isolation and characterization of dehydration-responsive element-binding factor 2C (MsDREB2C) from Malus sieversii Roem. Plant and Cell Physiology, 54(9): 1415-1430, 2013.

Publication Dates

  • Publication in this collection
    23 Nov 2020
  • Date of issue
    2020

History

  • Received
    26 May 2020
  • Accepted
    21 Oct 2020
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