The Mechanism Of Cathepsin Affects The Transmission Of Tomato Chlorosis Virus By Q Bemisia Tabaci

Tomato chlorosis virus(To CV)is an emerging threat to tomato crops in China that is mainly transmitted by Bemisia tabaci,it can co-infect with Tomato yellow leaf curl virus(TYLCV)in the field,causing serious economic losses on tomato production.Cathepsin is the main protease in lysosomes.It not only helps lysosomes to maintain cell homeostasis,but also releases from lysosomes as a digestive enzyme into the intestine to digest the proteins eaten by insects.Cathepsin plays a very important role in the process of immunity and intestinal digestion.In this research,we studied the influence of co-infection of To CV and TYLCV on the transmission of To CV,and screened out the significantly different cathepsin genes by transcriptome sequencing of Q whitefly feding on different infection ways of tomato.Then the mechanism of cathepsin effects in the process of transmission of To CV by B.tabaci was explored,which could provide the foundation for the study of the synergism of TYLCV and To CV and the interaction mechanism between plant-virus and vector insects.The main results were described as follows:1.The experiments of To CV transmission showed that the co-infection of To CV and TYLCV promoted the transmission ability of whitefly to To CV:the virus carrying rate of whitefly feded tomato co-infection To CV and TYLCV was 80%,and the copy number of To CV in whitefly reached 6.79×10~7 copies/μL after 48 AAP,that was significantly higher than the whitefly feded on tomato infected To CV;Only 25whitefly feded on co-infection tomato can cause a 100%transmission rate,while 50whiteflies feded on To CV infection tomato can cause a 100%transmission rate.2.A total of 135 differentially expressed genes(DEGs)were identified by transcriptome sequencing of Q whitefly feded on tomato two of different infection ways,with 79 up-regulated and 56 down-regulated genes.After compared with the KEGG database,we found that the differentially expressed genes were mainly concentrated in the lysosomal pathway,which Cath B and Cath F genes were the main genes.3.The activity of Cath F increased significantly in the early acquisition of To CV,and the activity of Cath B increased significantly when the concentration of To CV in whitefly reached saturation.The activity of Cath B and Cath F gradually declined with the loss of To CV in B.tabaci,and tended to normal level after 4 days.4.We measured the ability of acquisition,retention and spread of To CV by using enzyme inhibitor reduced Q whitefly cathepsin activity.The results showed that the accumulation of To CV in Q whitefly feded enzyme inhibitor group was significantly higher than the control group in the same acquisition and retention time of To CV,and20 B.tabaci transmission rate of To CV was about 80%after 48 h AAP,which was significantly higher than that of the control group which was 56%.It showed that the decrease of cathepsin activity improved the ability of Q whitefly to acquire,retain and transmit To CV.