Maternally inherited bacterial symbionts infecting arthropods have major implications on host ecology and evolution. Among them, the genus Arsenophonus has particular characteristics (large host spectrum, wide range of symbiotic relationships), making it a good model to study the evolution of host-symbiont associations. We realized a survey of
Arsenophonus diversity in whitefly species, especially the Bemisia tabaci species complex. This polyphagous pest,
composed of genetic groups that differ in many ecological aspects, harbor several lineages of Arsenophonus. The evolutionary history of these bacteria at a fine host taxonomic level was studied in association to host geographical range and ecology.
- Samples were screened for Arsenophonus infection by amplification of the 23s rRNA gene. B. tabaci genetic groups were identified based on the mtCOI gene. - Arsenophonus diversity was investigated on three genes, ftsK, yaeT and FbaA.
- Phylogenetic analyses were performed using maximum-likelihood (ML) and Bayesian inferences (BI) for the concatenated data set.
- Putative recombinant regions were searched using methods available in RDP3.
High diversity of Arsenophonus symbionts in B. tabaci.
Intergenic recombination events suggested that Arsenophonus is not a strict clonal bacterium. Some strains were found in other Hemiptera and could be the ancestral clade in whiteflies while others were found in Hymenoptera and Diptera and may have been acquired more recently by
whiteflies through horizontal transfers.
L. Mouton
1*, M. Thierry
2, H. Henri
1, R. Baudin
2, O. Gnankine
4, B. Reynaud
2, E. Zchori-Fein
5, N. Becker
3, F. Fleury
1and H. Delatte
2
Among 152 individuals, 19 allelic profiles and
6 phylogenetic groups of Arsenophonus have been identified which correlated with B. tabaci genetic groups (Fig. 2).
There is no evidence of intragenic recombination within the three genes but
intergenic recombination events were detected within 2 individuals belonging to the ASL genetic group from Burkina Faso (Fig. 2).
Phylogenetic analyses revealed the existence of 2 clades of Arsenophonus. One is composed of strains found in other Hemiptera and the other of strains found in Hymenoptera and Diptera (Fig. 3).
INTRODUCTION
MATERIALS AND METHODS
RESULTS
CONCLUSION
Phylogeny constructed with representative sequences of this study and sequences from Duron et al., 2010*. Recombinants were discarded. Bootstrap values (ML analysis) and posterior probability (BI) are shown at the nodes. Arsenophonus from H. equina was used as outgroup.
Strains retrieved from the literature are named by their host species and are in italics.
0.02 Hippobosca equina Trialeurodes vaporariorum Réunion Spain Burkina Faso Muscidifurax uniraptor Burkina Faso Burkina Faso Madagascar Seychelles Burkina Faso Cacopsylla alaterni Nasonia vitrepennis Pachycrepoideus vindemmiae Réunion Burkina Faso Triatoma infestans Aphis spiraecola Burkina Faso Burkina Faso Spain Bemisia tabaci Réunion Burkina Faso Protocalliphora azurea Triatoma guasayna Réunion Tanzania Aphis gossypii Madagascar Réunion Spalangia cameroni 99/1 100/1 100/1 100/1 60/0.96 98/1 94/0.99 60/0.77 100/1 84/0.95 82/0.95 T. vaporariorum Ms Ms Q2 ASL B. afer ASL AnSL Q3
Bootstrap values (ML analysis) and posterior probability (BI) are shown at the nodes. The tree was midpoint rooted. Recombinant individuals are indicated in red.
ASL + AnSL Q3 ASL Ms Q2 T. vaporariorum + Ms B. afer 0.05 100/1 100/1 86/1 92/1 100/1 96/1 99/1 98/1 B1-47 (Burkina Faso) B1-42 (Burkina Faso) Réunion Réunion (Ms) Réunion (T. vaporariorum) Tanzania (Ms) Madagascar (Ms) Tanzania (Ms) Réunion Israel France Spain Burkina Faso Burkina Faso Togo Burkina Faso Burkina Faso Togo Burkina Faso Madagascar Mauritius Seychelles Mayotte Réunion
Evidence of diversity and recombination in
Arsenophonus symbionts of the Bemisia tabaci
species complex
Q2, Q3, AnSL, ASL and Ms indicate the genetic groups of Bemisia tabaci.
Samples were collected in mainland France (FR), Spain (ES), Israel (IL), Burkina Faso (BF), Togo (TG), Benin (BJ), Tanzania (TZ), Seychelles (SC), Comoros Grande Comore (KM), Mayotte (YT), Madagascar (MG), Mauritius (MU) and Reunion (RE).
Figure 1. Sampling sites and prevalence of Arsenophonus (blue) among whiteflies
Figure 2. Phylogeny of Arsenophonus from whitefly species
Figure 3. Phylogeny of symbiotic Arsenophonus of arthropods
*Duron, O., T. Wilkes, and G. Hurst. 2010. Interspecific transmission of a male-killing bacterium on an ecological timescale. Ecology Letters 13: 1139-1148.
Q2 (FR) Q2 (ES) ASL (BF) AnSL (TG) AnSL (BJ) Q2 (IL) (SC) Ms (KM) Ms (YT) Ms (MG) Ms (MU) Ms Ms (TZ) 28% 73% 83% 35% 65% 11% 66% 35% 20% 57% 75% (RE) T. vaporariorum Q3 (BF) (RE) B. afer (RE) Ms (RE) Q2 100% 92% 100% 100% 100% 100%
1 Université Claude Bernard Lyon 1, Laboratoire de Biométrie et Biologie Evolutive, Villeurbanne, France ; 2 CIRAD, UMR Peuplements Végétaux et Bioagresseurs en Milieu Tropical,Saint Pierre La Réunion, France
4 Université de Ouagadougou, Laboratoire d’Entomologie Fondamentale et Appliquée, Ouagadougou , Burkina Faso ; 5 Agricultural Research Organization, Department of Entomology, Newe Ya'ar Research Center, Ramat Yishay, Israel 3 Museum National d’Histoire Naturelle, Structure et Evolution de la Biodiversité, Paris, France.
*laurence.mouton@univ-lyon1.fr
Grande Comore Tanzania
Mouton, Thierry et al., BMC Microbiology (in press)