Transcriptome analysis reveals TOR signalling-mediated plant flush shoots governing Diaphorina citri Kuwayama oviposition.

ABSTRACT

Asian Citrus Psyllid (ACP), Diaphorina citri, is a key vector transmitting the causative agent of Huanglongbing (HLB) disease. Population growth of ACP is evident after feeding on plant flush shoots, as they only oviposit here. However, the underlying mechanism as to why flush shoots govern oviposition is unclear. This study compares the fecundity and ovarian morphology of ACP between young flush and mature leaves. Furthermore, the transcriptome of mated females infesting Murraya paniculata was analysed. Finally, the gene of the key Target of Rapamycin (TOR) signalling pathway was silenced by RNAi. Results indicated that flush shoot feeding activated the development of the psyllids ovary and therefore induced oviposition. A total of 126 and 2794 differentially expressed genes were detected at 1 and 5 days, respectively, after pest infestation of flush shoots compared to mature leaves. Many genes are involved in protein metabolism, Mitogen-Activated Protein Kinase (MAPK) signalling pathway, hormone synthesis, and TOR signalling pathway all thought to activate reproduction. Silencing of the positive regulator gene DcRheb in the TOR pathway resulted in lower levels of ecdysone and juvenile hormone and decreased vitellogenin synthesis, further disrupting reproductive ability. This study enhances understanding of the molecular mechanism underlying ACP's reproductive strategy.