Abstract NAC transcription factors are plant-specific proteins involved in many processes during the plant life cycle and responses to biotic and abiotic stresses. Previous studies have shown that stress-induced OsNAC5 from rice (Oryza sativa L.) is up-regulated by senescence and might be involved in control of iron (Fe) and zinc (Zn) concentrations in rice seeds. Aiming a better understanding of the role of OsNAC5 in rice plants, we investigated a mutant line carrying a T-DNA insertion in the promoter of OsNAC5, which resulted in enhanced expression of the transcription factor. Plants with OsNAC5 enhanced expression were shorter at the seedling stage and had reduced yield at maturity. In addition, we evaluated the expression level of OsNAC6, which is co-expressed with OsNAC5, and found that enhanced expression of OsNAC5 leads to increased expression of OsNAC6, suggesting that OsNAC5 might regulate OsNAC6 expression. Ionomic analysis of leaves and seeds from the OsNAC5 enhanced expression line revealed lower Fe and Zn concentrations in leaves and higher Fe concentrations in seeds than in WT plants, further suggesting that OsNAC5 may be involved in regulating the ionome in rice plants. Our work shows that fine-tuning of transcription factors is key when aiming at crop improvement. plantspecific specific stresses stressinduced stress induced OsNAC Oryza L. L upregulated up regulated (Fe (Zn plants TDNA T DNA factor maturity addition coexpressed co expressed finetuning fine tuning improvement

Abstract Oryza sativa, the common cultivated rice, is one of the most important crops for human consumption, but production is increasingly threatened by abiotic stresses. Although many efforts have resulted in breeding rice cultivars that are relatively tolerant to their local environments, climate changes and population increase are expected to soon call for new, fast generation of stress tolerant rice germplasm, and current within-species rice diversity might not be enough to overcome such needs. The Oryza genus contains other 23 wild species, with only Oryza glaberrima being also domesticated. Rice domestication was performed with a narrow genetic diversity, and the other Oryza species are a virtually untapped genetic resource for rice stress tolerance improvement. Here we review the origin of domesticated Oryza sativa from wild progenitors, the ecological and genomic diversity of the Oryza genus, and the stress tolerance variation observed for wild Oryza species, including the genetic basis underlying the tolerance mechanisms found. The summary provided here is important to indicate how we should move forward to unlock the full potential of these germplasms for rice improvement.