Wolbachia infection in Argentinean populations of Anastrepha fraterculus sp1: preliminary evidence of sex ratio distortion by one of two strains

Abstract

BackgroundWolbachia, one of the most abundant taxa of intracellular Alphaproteobacteria, is widespread among arthropods and filarial nematodes. The presence of these maternally inherited bacteria is associated with modifications of host fitness, including a variety of reproductive abnormalities, such as cytoplasmic incompatibility, thelytokous parthenogenesis, host feminization and male-killing. Wolbachia has attracted much interest for its role in biological, ecological and evolutionary processes as well as for its potential use in novel and environmentally-friendly strategies for the control of insect pests and disease vectors including a major agricultural pest, the South American fruit fly, Anastrepha fraterculus Wiedemann (Diptera: Tephritidae).ResultsWe used wsp, 16S rRNA and a multilocus sequence typing (MLST) scheme including gatB, coxA, hcpA, fbpA, and ftsZ genes to detect and characterize the Wolbachia infection in laboratory strains and wild populations of A. fraterculus from Argentina. Wolbachia was found in all A. fraterculus individuals studied. Nucleotide sequences analysis of wsp gene allowed the identification of two Wolbachia nucleotide variants (named wAfraCast1_A and wAfraCast2_A). After the analysis of 76 individuals, a high prevalence of the wAfraCast2_A variant was found both, in laboratory (82%) and wild populations (95%). MLST analysis identified both Wolbachia genetic variants as sequence type 13. Phylogenetic analysis of concatenated MLST datasets clustered wAfraCast1/2_A in the supergroup A. Paired-crossing experiments among single infected laboratory strains showed a phenotype specifically associated to wAfraCast1_A that includes slight detrimental effects on larval survival, a female-biased sex ratio; suggesting the induction of male-killing phenomena, and a decreased proportion of females producing descendants that appears attributable to the lack of sperm in their spermathecae.ConclusionsWe detected and characterized at the molecular level two wsp gene sequence variants of Wolbachia both in laboratory and wild populations of A. fraterculus sp.1 from Argentina. Crossing experiments on singly-infected A. fraterculus strains showed evidence of a male killing-like mechanism potentially associated to the wAfraCast1_A - A. fraterculus interactions. Further mating experiments including antibiotic treatments and the analysis of early and late immature stages of descendants will contribute to our understanding of the phenotypes elicited by the Wolbachia variant wAfraCast1_A in A. fraterculus sp.1.

Wolbachia pipientis Associated With Tephritid Fruit Fly Pests: From Basic Research to Applications

“…Adequate assessment of fertilization must be performed to ensure that failed embryos are not confused with unfertilized eggs. This may require testing for insemination of females that produce no larval progeny (e.g., Zabalou et al, 2009;Conte et al, 2019), or exclusion of females that predominantly lay unfertilized eggs, such as old Drosophila melanogaster virgin females (Menon et al, 2014).…”

Wolbachia pipientisassociated to tephritid fruit fly pests: from basic research to applications

“…Based mostly on PCR and sequencing approaches, ˜66% of ˜86 tephritid species screened have at least one record of positive Wolbachia infection (excluding pseudogenes) in laboratory and natural populations (Table S1; only supergroups A and B have been found in tephritids). For the genus Anastrepha , all but one species ( A. ludens ) of 17 screened to date harbor Wolbachia [142, 144–148, 149; and this study, 150]. Most Anastrepha species harbor Wolbachia strains assigned to supergroup A. Anastrepha striata Schiner and Anastrepha serpentina Wiedemann, however, harbor supergroup B in southern Mexico [147; and this study] and supergroup A in Brazil [146].…”

“…Most Anastrepha species harbor Wolbachia strains assigned to supergroup A. Anastrepha striata Schiner and Anastrepha serpentina Wiedemann, however, harbor supergroup B in southern Mexico [147; and this study] and supergroup A in Brazil [146]. Up to three Wolbachia sequence types have been detected per locality within morphotypes of the A. fraterculus complex [142, 150], but co-infection of a single individual is generally not observed [except for one report in A. fraterculus ; 151].…”

“…A recent study by Conte et al [142] examined the phenotypic effects induced by two Wolbachia strains native to A. fraterculus (sp1). No evidence of bidirectional cytoplasmic incompatibility was detected in reciprocal crosses.…”

“…the recent discovery of Spiroplasma in two species of Glossina; 229]. With few exceptions [142, 147; Asimakis et al, unpublished, 230], research on tephritid facultative heritable bacteria has not examined the possibility of players other than Wolbachia . Therefore, we urge that such research include screens for other symbionts, including viruses, protozoans, and fungi.…”