The Mechanism Of Autophagy In The Whitefly-begomovirus Interactions

As the only known vector of Begomovirus, whitefly Bemisia tacbaci (Gennadius) plays a critical role in the spread of these virus. During recent years, serious damages of begomoviruses and whiteflies have triggered a large body of research on the interactions between whiteflies and begomoviruses. However, little has been known about the role of autophagy in the interactions of insect vectors with the plant viruses which they transmit. Previously, we have shown that TYLCV infection can induce autophagy in whitefly, on the other hand, activation of autophagy suppressed the accumulation of virus in whitefly. Nevertheless, how does autophagy happen in whitefly? How do viruses take advantages of autophagy? Is there non-selective autophagy in infected whitefly? And whether autophagy could be detected in all the infected whitefly? The address to these four questions could provide reference to further study on whitefly inherited immune mechanisms, and extended to the study on unique mechanism of whitefly transmission of viruses.This research focused on the influences of three viruses TYLCV, TYLCCNV and PaLCuCNV on whitefly B. tabaci autophygical pathway, to identify the possible role of autophagy in the process of anti-virus. The research included, morphological analysis on the present of whitefly autophagy flux using TEM; applying inhibitor and RNAi method to block autophagy pathway, to describe the relationship between viruses and autophagy; applying specific inducer and inhibitor to whitefly for analyzing the accumulation of viruses and transmission efficiency, and to demonstrate the function of autophagy in the interactions between TYLCV and insects. The study also explored the accumulation of different begomovirus, to realize whether virus reproduction is related to autophagy and to give new insight into autophagy and virus reproduction. At last, this study revealed the possible presence of selective autophagy in TYLCV infected MEAM1 and provided evidence for selective autophagy in insects. (1) Influence of TYLCV infection on MEAM1 autophagy fluxAfter the infection of TYLCV, TEM demonstrated the presence of autophagyflux. The result of Western Blot further confirmed that autophagy present not in a point, however is a flux in process; IF revealed the relationship between TYLCV-CP and autophagysome, indicating the activation of autophagy signal after TYLCV infection.(2) Influence on TYLCV accumulation in whitefly by autophagyAfter MEAM1 was subjected to inhibitor, qPCR and Western Blot presented obvious accumulation of TYLCV-DNA and CP in whitefly. Experiment on virus transmission indicated that the inhibition of autophagy led to the increase in virus transmission. RNAi experiment which blocks the pathway of autophagy also resulted in the increase in accumulation of TYLCV in whitefly. In conclusion, inhibition of autophagy pathway enhanced the accumulation of TYLCV in whitefly and the transmission.(3) Influence of TYLCCNV and PaLCuCNV on MEAM1 autophagyIt is revealed by Western Blot that the turnover of LC3-II (autophagy marker protein) increased after the infection of TYLCCNV, which is similar to the infection of TYLCV. Thus, TYLCCNV could also activate autophagy pathway after infection. Nevertheless, PaLCuCNV could not activate autophagy pathway. Besides, TYLCV could not go through midgut barrier of Trialeurodes vaporariorum and activate autophagy pathway.(4) Possible presence of selected autophagy in MEAM1 after TYLCV infectionThe presence of autophagysome indicated possible mitocondrialsome in MEAM1 by using TEM, with consistent infection of TYLCV. In addition, the results of colocalization of LAMP-2A and virus coat protein can provide the evidence for CMA may happen in the MEAM1 whitefly infected by TYLCV.