Thao, MyLo Ly

ABSTRACT Whiteflies (Hemiptera: Sternorrhyncha: Aleyrodidae) are plant sap-sucking insects that harbor prokaryotic primary endosymbionts (P-endosymbionts) within specialized cells located in their body cavity. Four-kilobase DNA fragments containing 16S-23S ribosomal DNA (rDNA) were amplified from the P-endosymbiont of 24 whiteflies from 22 different species of 2 whitefly subfamilies. In addition, 3-kb DNA fragments containing mitochondrial cytB , nd1 , and large-subunit rDNA (LrDNA) were amplified from 17 whitefly species. Comparisons of the P-endosymbiont (16S-23S rDNA) and host ( cytB - nd1 -LrDNA) phylogenetic trees indicated overall congruence consistent with a single infection of a whitefly ancestor with a bacterium and subsequent cospeciation (cocladogenesis) of the host and the P-endosymbiont. On the basis of both the P-endosymbiont and host trees, the whiteflies could be subdivided into at least five clusters. The major subdivision was between the subfamilies Aleyrodinae and Aleurodicinae . Unlike the P-endosymbionts of may other insects, the P-endosymbionts of whiteflies were related to Pseudomonas and possibly to the P-endosymbionts of psyllids. The lineage consisting of the P-endosymbionts of whiteflies is given the designation “ Candidatus Portiera” gen. nov., with a single species, “ Candidatus Portiera aleyrodidarum” sp. nov.

ABSTRACT Mealybugs (Hemiptera, Coccoidea, Pseudococcidae) are plant sap-sucking insects that have within their body cavities specialized cells containing prokaryotic primary endosymbionts (P-endosymbionts). The P-endosymbionts have the unusual property of containing within their cytoplasm prokaryotic secondary endosymbionts (S-endosymbionts) [C. D. von Dohlen, S. Kohler, S. T. Alsop, and W. R. McManus, Nature (London) 412:433-436, 2001]. Four-kilobase fragments containing 16S-23S ribosomal DNA (rDNA) were obtained from the P-endosymbionts of 22 mealybug species and the S-endosymbionts of 12 representative species. Phylogenetic analyses of the P-endosymbionts indicated that they have a monophyletic origin and are members of the β-subdivision of the Proteobacteria ; these organisms were subdivided into five different clusters. The S-endosymbionts were members of the γ-subdivision of the Proteobacteria and were grouped into clusters similar to those observed with the P-endosymbionts. The S-endosymbiont clusters were distinct from each other and from other insect-associated bacteria. The similarity of the clusters formed by the P- and S-endosymbionts suggests that the P-endosymbionts of mealybugs were infected multiple times with different precursors of the S-endosymbionts and once the association was established, the P- and S-endosymbionts were transmitted together. The lineage consisting of the P-endosymbionts of mealybugs was given the designation “ Candidatus Tremblaya” gen. nov., with a single species, “ Candidatus Tremblaya princeps” sp. nov. The results of phylogenetic analyses of mitochondrial DNA fragments encoding cytochrome oxidase subunits I and II from four representative mealybug species were in agreement with the results of 16S-23S rDNA analyses, suggesting that relationships among strains of “ Candidatus T. princeps” are useful in inferring the phylogeny of their mealybug hosts.