Insect Science

It has long been known that armored scale insects harbor endosymbiotic bacteria inside specialized cells called bacteriocytes. Originally, these endosymbionts were thought to be fungal symbionts but they are now known to be bacterial and have been named Uzinura diaspidicola. Bacteriocyte and endosymbiont distribution patterns within host insects were visualized using in situ hybridization via 16S rRNA specific probes. Images of scale insect embryos, eggs and adult scale insects show patterns of localized bacteriocytes in embryos and randomly distributed bacteriocytes in adults. The symbiont pocket was not found in the armored scale insect eggs that were tested. The pattern of dispersed bacteriocytes in adult scale insects suggest that Uzinura and Blattabacteria may share some homologous traits that coincide with similar life style requirements, such as dispersal in fat bodies and uric acid recycling.

Abstract Previously, we reported that Candidatus Liberibacter asiaticus (Las)‐infected Diaphorina citri are characterized by lower levels of cytochrome P450 monooxygenases than uninfected counterparts. In the present study, we investigated expression levels of family 4 cytochrome P450 ( CYP4 ) genes in Las‐infected and uninfected D. citri adults. Five novel CYP4 genes ( CYP4C67 , CYP4DA1 , CYP4C68 , CYP4DB1 and CYP4G70 ) were identified. Four of the five CYP4 genes were expressed at significantly higher levels in uninfected than Las‐infected males, whereas only one was expressed at significantly higher levels in uninfected than Las‐infected females. These results suggest that levels of cytochrome P450 monooxygenases in D. citri may be linked to expression levels of these CYP4 genes. Expression of all five CYP4 genes was induced by exposure of D. citri to imidacloprid, suggesting their possible involvement in metabolism of this toxin. Higher expression of the five CYP4 genes was found in nymphs than adults, which is congruent with previous results indicating higher levels of cytochrome P450 monooxygenases in nymphs than adults. These five CYP4 genes may be promising candidates for RNA‐interference to silence overexpression of genes associated with insecticide resistance in D. citri . These newly identified genes may also serve as DNA‐based screening markers for cytochrome P450‐mediated insecticide resistance in field populations of D. citri .