Occurrence of Wolbachia in Brazilian samples of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

Ocorrência de Wolbachia em amostras Brasileiras da Mosca-do-Mediterrâneo, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

SCIENTIFIC NOTE

Occurrence of Wolbachia in Brazilian samples of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

Ocorrência de Wolbachia em amostras Brasileiras da Mosca-do-Mediterrâneo, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

Lincoln S. Rocha^{I, II}; Rodrigo O. Mascarenhas^I; André L.P. Perondini^I; Denise Selivon^I

^IDepto. Biologia, Instituto de Biociências, Univ. São Paulo, 05508-900, São Paulo, SP [e-mail]

^IIEndereço atual: Lab. Parasitologia, Instituto Butantan, Av. Vital Brazil 1500, 05503-900, São Paulo, SP

ABSTRACT

Wolbachia bacteria were detected by PCR followed by sequencing of a fragment of the 16S ribosomal gene, in a natural population sample and in two laboratory colonies of the medfly, C. capitata (Wied.), from Brazil. Sequencing revealed that the fragment was compatible with the Wolbachia type A group found in several insect species. This is the first description of a natural Wolbachia infection in C. capitata, since several other samples from different regions so far analyzed seemed to be free of infection.

Key words: Bacteria, medfly, endosymbiont

RESUMO

Bactérias Wolbachia foram detectadas por PCR seguido de seqüenciamento de um segmento do gene ribossomal 16S em uma amostra de população natural e em duas colônias de laboratório de Ceratitis capitata (Wied.) do Brasil. O seqüenciamento do fragmento amplificado mostrou que este é compatível com os de Wolbachia tipo A, encontrada em numerosas espécies de insetos. Esta é a primeira descrição de uma infecção natural desse hospedeiro por Wolbachia desde que, em linhagens de C. capitata provenientes de outras regiões, não foram encontradas essas bactérias.

Palavras-chave: Bactéria, endossimbionte

Wolbachia are intracellular alpha-proteobacteria which infest a very large number of arthropods usually affecting their reproductive biology, inducing feminization, parthenogenesis, male killing and cytoplasmic incompatibilities (Werren 1997). The bacteria are transovarially inherited, but may be transmitted horizontally between taxa (Vavre et al. 1990, Heath et al. 1994). Moreover, artificial transfection has been successfully achieved among several insect species (Braig et al. 1994, Sasaki et al. 2002, Riegler et al. 2004). Due to their ability to manipulate their hosts' reproduction, causing incompatibilities among strains, the use of these bacteria as agents for insect-pest biological control or population suppression has been suggested as an alternative to the sterile insect technique (SIT) (Beard et al. 1993, Sinkins et al. 1997).

Wolbachia was reported to infest species of the tephritid fruit flies (Werren et al. 1995, Kittayapong et al. 2000, Selivon et al. 2002, Riegler & Stauffer 2002), but has not been found in several established strains of the medfly Ceratitis capitata (Wied.) (Bourtzis et al. 1994). Zabalou et al. (2004), successfully infected a medfly strain with Wolbachia derived from the tephritid Rhagoletis cerasi (L.). Laboratory tests showed that the bacteria induced cytoplasmic incompatibilities in the new host indicating its potential use as an alternative method for the control of these insect-pest populations.

The medfly was introduced in Brazil, where it was first detected in 1901 by Ihering. Since then, it has spread over the country and became a major pest of fruit culture, attacking a large number of commercial fruits (Zucchi 2001). During a screening for Wolbachia in Brazilian fruit flies, we found samples of C. capitata which were infected by this endosymbiont. For our knowledge, this is the first report on a natural infection of C. capitata by Wolbachia. Since this information might be useful for control programs of this insect-pest (see Zabalou et al. 2004), we report herein the data on Wolbachia naturally infecting the medfly in Brazil.

Three samples of C. capitata were examined for the presence of Wolbachia. One sample came from a natural population collected in oranges from São Bento do Sapucaí, State of São Paulo (22º46'S/ 45º04'W), and the others, from laboratory colonies maintained at the Centro de Energia Nuclear na Agricultura (CENA/USP) and in our laboratory at the Universidade de São Paulo, all originally collected in Brazilian regions.

Total DNA of C. capitata was extracted from adult females and embryos according to the technique described by Jowett (1998). Detection of Wolbachia was done by PCR in 10 individual specimens of each sample, using the primers WSpec-f 5'-CATACCTATTCGAAGGGATAG- 3' and WSpec-r 5'-AGCTTCGAGTGAAACCAATTC- 3', which amplify a 438 bp fragment of the 16S rDNA gene (Werren & Windsor 2000). The PCR reaction was carried out with 3µl DNA sample, 2.5µl 10x buffer, 0.75µl MgCl₂ (50mM), 1µl nucleotide mix (5mM each), 0.35µl (20mM) of each primer, 0.25µl Taq Polymerase (Gibco BRL Life Technologies), completed with distilled deionized water to a final volume of 25µl. The W-Spec amplification conditions consisted of two cycles of two min at 95ºC, one min at 60ºC, one min at 72ºC, 35 cycles of 30 s at 95ºC, one min at 60ºC, 45 s at 72ºC and a final extension of five min at 72ºC (Werren & Windsor 2000).The presence of the amplified fragment was checked by electrophoresis on 1.5% agarose gel. The PCR-amplified DNA fragments were sequenced using the two primers above decribed and the Big Dye system (Applied Biosystems) in an automated DNA sequencer ABI377 (Applied Biosystems). Sequence analyses and alignments were made using the software Sequence Navigator (Applied Biosystems) and BLAST at NCBI (National Center of Biotechnology Information, www.ncbi.nih.gov/BLAST).

The Wolbachia-specific 16S rDNA 438bp fragment was detected in all individuals from the three samples of C. capitata. Seven amplified fragments were totally sequenced, being four from the natural population sample and three from our laboratory colony. A reliable internal portion of 365 bp of the sequence was used in the following sequence analysis. The sequences were identical within and among samples and are available at the GenBank website (www.ncbi.nih.gov, accession # AY910011). The sequence obtained from the fragment showed 95% to 98% identity with Wolbachia type A sequences from a large number of insect species available at the GenBank database. Eleven bacterial sequences reached the condition e-value = 0, among which the most similar to the Wolbachia sequence here found were from coleopterans [Diabrotica virgifera Le Conte, D. cristata Le Conte, D. lemniscata Le Conte (acession # AY007551, AY007550, AY007547, respectively)], hymenopterans [Nasonia longicornis Darling, N. giraulti Darling (acession # M84691, M84690, respectively), and the dipteran Phlebotomus papatasi (Scopoli) (acession # U80584). The data on Wolbachia from tephritid flies (Werren et al. 1995, Kittayapong et al. 2000, Riegler & Staufer 2002), including brazilian samples of the Anastrepha sp2 aff. fraterculus (Selivon et al. 2002) and from the lepidopteran parasitoid Trichogramma atopovirilia Oatman & Platner (Ciociola et al. 2001) could not be used for these comparisons since fragments of different genes were amplified.

For our knowledge, this is the first record of Wolbachia being naturally hosted by the fruit fly C. capitata. The fact that Wolbachia was not found in many other strains of C. capitata (Bourtzis et al. 1994, Zabalou et al. 2004) suggests that this insect might have acquired a neotropical strain of Wolbachia after its introduction in Brazil. Unfortunately, the thirty sequences (including the above mentioned), ranging from 95-98% similarity to the sequence here found in C. capitata, were from insects sampled outside the neotropical region and could not be used to test this hypothesis. An alternative hypothesis would be that the introduced flies derived from populations which were infected with Wolbachia, although this infection was not yet detected. Further analysis on neotropical insects could provide clues on the origin of Wolbachia infection in Brazilian strains of C. capitata.

Acknowledgment

The authors would like to thank Dr. Julio M. M. Walder for providing the C. capitata sample from the Centro de Energia Nuclear na Agricultura. This study was supported by FAPESP (98/10701-4 and 03/02698-7) and CNPq. ROM is recipient of a master's degree scholarship (CNPq), LSR had a PhD scholarship from FAPESP; DS and ALPP are fellows of CNPq.

Literature Cited

Received 18/II/05. Accepted 24/V/05.

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Publication Dates

• Publication in this collection
  20 Mar 2006
• Date of issue
  Dec 2005

History

• Received
  18 Feb 2005
• Accepted
  24 May 2005