ThewMelWolbachiastrain was known for cytoplasmic incompatibility (CI)-induction and blocking the transmission of dengue. However, it is unknown whether it can establish and induce CI in a non-dipteran host insect. Here we artificially transferredwMel fromDrosophila melanogasterinto the whiteflyBemisia tabaci. Fluorescencein situhybridisation demonstrated thatwMel had successfully transfected the new host. Reciprocal crossing was conducted withwMel-transfected and wild-type isofemale lines, indicating thatwMel could induce a strong CI without imposing significant cost on host fecundity. We then determined the maternal transmission efficiency ofwMel in the offspring generations, showing a fluctuating trend over a period of 12 generations. We thus detected the titre ofwMel during different developmental stages and in different generations by using real-time quantitative PCR, revealing a similar fluctuating mode, but it was not significantly correlated with the dynamics of transmission efficiency. These results suggest thatwMel can be established inB.tabaci, a distantly related pest insect of agricultural importance; moreover, it can induce a strong CI phenotype in the recipient host insect, suggesting a potential for its use in biological control ofB. tabaci.

Geranylgeranyl diphosphate synthase (GGPP synthase or GGPPS) is among the short-chain prenyltransferases, catalyzing the formation of the acyclic precursor GGPP for the biosynthesis of a variety of isoprenoids. GGPPSs have been extensively studied in plants, eubacteria, archaebacteria, yeast and mammals, but up to now information about an insect GGPPS is still scarce. Here we cloned the cDNA encoding an insect GGPPS from the cotton aphid (designated as AgGGPPS). AgGGPPS had an open reading frame of 930 bp, coding for 309 amino acids, with a theoretical pI/Mw of 6.21/35.7kDa. Sequence analysis showed that the amino acid sequence of AgGGPPS included the conserved aspartaterich motifs characterized by all prenyltransferases known to date, and could be classified as type-III GGPPS. Phylogenetic analysis showed that all animal GGPPSs were placed in a large group next to fungal GGPPS, and plant and bacterial GGPPSs formed another large group. AgGGPPS was over-expressed in Escherichia coli, and recombinant protein was purified by affinity chromatography. In vitro enzymatic activity assay coupled with product identification by gas chromatography- mass spectrometry demonstrated that AgGGPPS could catalyzed the formation of GGPP with DMAPP, GPP or FPP as the allylic cosubstrates in the presence of IPP, suggesting that AgGGPPS accepted not only FPP but also GPP and DMAPP as the allylic cosubstrate, different from other type-III GGPPSs which accepted only FPP as the allylic cosubstrate. This is the first report that a novel catalytic property exists in the type-III animal GGPPSs.