The phenylalanine synthesized by whitefly–Portiera symbiosis enhances host survival under fungi infection

The metabolic cooperation for the phenylalanine synthesis between the host and its obligate symbiont is widespread in hemipteran insects. However, the mechanisms underlying phenylalanine synthesis and its role in hemipteran insects are largely unknown. Our previous study indicates that the whitefly Bemisia tabaci glutamate–oxaloacetate transaminase gene GOT2 compensates for tyrB missing from Portiera. Here, we found that the whitefly GOT2 and Portiera can cooperate for the synthesis of phenylalanine mainly by silencing GOT2. We further revealed that the phenylalanine synthesized by whitefly–Portiera symbiosis promotes cuticle formation on adult whiteflies. Then, we demonstrated that repression of phenylalanine synthesis by silencing whitefly GOT2 does not significantly increase the whitefly mortality under high temperature and low humidity conditions, but it enhances the whitefly mortality when whiteflies were infected with the entomopathogenic fungi Beauveria bassiana. Our results provide experimental evidence on how symbiosis contributes to adult whitefly cuticle formation, revealing parallel histories of the phenylalanine synthesized by the host and its obligate symbiont facilitated cuticle formation in insects housing the bacteriocyte symbionts. This study indicates that the phenylalanine synthesized by insect–bacteria symbiosis may confer the insect adaptation to entomopathogenic fungi. Our findings will also help us to develop an insect symbiosis disruption strategy for pest control.