Four phospholipase A 2 genes encoded in the western flower thrips genome and their functional differentiation in mediating development and immunity

Eicosanoids are synthesized from phospholipids by the catalytic activity of phospholipase A (PLA ). Even though several PLA s are encoded in the genome of different insect species, their physiological functions are not clearly discriminated. This study identified four PLA genes encoded in the western flower thrips, Frankliniella occidentalis. Two PLA s (Fo-PLA C and Fo-PLA D) are predicted to be secretory while the other two PLA s (Fo-PLA A and Fo-PLA B) are intracellular. All four PLA genes were expressed in all developmental stages, of which Fo-PLA B and Fo-PLA C were highly expressed in larvae while Fo-PLA A and Fo-PLA D were highly expressed in adults. Their expressions in different tissues were also detected by fluorescence in situ hybridization. All four PLA s were detected in the larval and adult intestines and the ovary. Feeding double-stranded RNAs specific to the PLA genes specifically suppressed the target transcript levels. Individual RNA interference (RNAi) treatments led to significant developmental retardation, especially in the treatments specific to Fo-PLA B and Fo-PLA D. The RNAi treatments also showed that Fo-PLA B and Fo-PLA C expressions were required for the induction of immune-associated genes, while Fo-PLA A and Fo-PLA D expressions were required for ovary development. These results suggest that four PLA s are associated with different physiological processes by their unique catalytic activities and expression patterns.