Effects Of Bemisia Tabaci(Gennadius)Feeding And Exogenous JA Treatment On Endogenous JA And SA Of Capsicum Annuum L.

Capsicum annuum L.,popular vegetable widely cultivated throughout the country,is often plagued with a variety of pests and diseases during the production,among which,Bemisia tabaci(Gennadius))is one of the most major pests that endanger the production of C.annuum L.Activity of Bemisia tabaci in the planting areas often leads to yield reduction of peppers,In severe cases,the yield loss can reach more than 70%,and even up to 100%.At present,chemical methods are mainly used to control B.tabaci.But with the long-term use of chemical pesticides,the resistance of Bemisia tabaci to the pesticides increased,leading to increased ecological risk.Our previous studies have shown that B.tabaci has obvious selectivity for the feeding of different varieties of pepper,and the resistant varieties shown less feeding opptunity and caused less damage after feeding compared with the susceptible varieties.Therefore,uncover the resistance mechanism of pepper varieties to B.tabaci and breeding/screening pepper varieties resistant to B.tabaci is an feasible way to improve the quality and yield of peppers.The plant resistance to insect pests can be divided into inducible resistance and constitutive resistance.Exogenous jasmonic acids(JA)and Methyl jasmonate(MeJA)can induce plants to produce resistant substances that have repellent action against pests and achieve defense purposes.In this study,the susceptible pepper cultivars Sujiao No.15 and the resistant cultivar Xinsujiao No.5 were selected as research materials,and they were treated with B.tabaci feeding and exogenous MeJA.Induced responses in defances hormones(JA,SA)and relative gene expression level envolved in JA and SA synthesis and signal transduction were checked by physiological and molecular biological methods respectively.We also analyzed the protemic changes before and after treatment in pepper leaves by using the isobaric tags for relative and absolute quantification(iTRAQ)proteome methods.Our results could be the theoretical foundation for elucidating the resistance mechanism of pepper to to B.tabaci at the molecular level.The main findings are as follows:1.To research on the different responces of B.tabaci feeding on different varieties of pepper(susceptible variety Sujiao No.15,resistant variety Xinsujiao No.5),we determined the inner JA and SA contents of pepper leaves feeding by the different pest population(0 head/leaf,30 heads/leaf,60 heads/leaf,90 heads per head)at a set time(48 h)and a set population of pests(60 head/leaf)feeding for a prolonged time(96 h).Relatively experession level of genes related to JA and SA synthesis and signal transduction(LOX,AOS,AOC,OPR3,EDS5,PAD4,WRKY70)were also be studid.The results showed that the content of JA in leaves of resistant cultivars was relatively low and that of SA was relatively high compared with that of susceptible pepper cultivars.The JA and SA contents in the leaves of two varieties were significantly affected when the population density of B.tabaci was 60 heads/leaf.After the B.tabaci feeding,the JA content in the sensible and resistant pepper leaves first decreased and then increased trend.The trend of SA content was opposite to that of JA.After B.tabaci feeding,the SA content of both varieties showed a trend of first increasing and then decreasing.Analyiss also showed that,within a certain period of time(24-96 h),the contents of JA and SA in the leaves of susceptible and resistant peppers all increased significantly compared with their control.and the resistance The increasing rate in resistant species is higher than that of susceptible species.Using RT-PCR to further analyze the expression levels of JA,SA synthesis and signal transduction pathway related genes at the molecular level,the results showed that B.tabaci could induced the increase expression levels of JA synthesis related genes LOX,AOC and SA transport related gene EDS5 in the resistant varieties.2.The effects of exogenous MeJA on the contents of JA and SA and the relatively expression levels of JA and SA related genes in pepper leaves were studied by spraying 10-5 mol/L MeJA on plantlets of two pepper varieties..The results showed that the content of JA increased significantly in susceptible and resistant pepper leaves after exogenous application of MeJA.The sensible variety reached its maximum at 12 hours after treatment,while the resistant cultivar reached its maximum at 24 hours.Exogenous MeJA also induced SA content changes in pepper leaves.The SA contents in susceptible and resistant varieties first decreased and then increased,but shown no significant difference in statistical analysis.RT-PCR results displayed up-regulated expression levels of JA synthesis related genes such as LOX,AOC and OPR3 in resistant cultivars and no significant up-regulation,in sensible cultivars after treatment with MeJA,indicating that the treatment of MeJA can effectively induce the expression of endogenous JA synthesis and gene expression related to the signal transduction pathway in pepper,and synthesize a large amount of JA,which plays an important role in plant resistance to insects.3.To further explore the role of JA and SA-associated proteins and other possible defense-related proteins in the induction of resistance of pepper in response to whitefly feeding and exogenous JA induction,the method of isotopically labeled relative and absolute quantification(iTRAQ)were used to compare the relatively proteomic experession level in pepper leaves before and after B.tobaci feeding and the treatment of MeJA.A total of 149 differentially expression proteins(DEPs)were identified.By bioinformatics analysis,these proteins belonged to stimuli-responsive and defense-related proteins 42(28.19%),36 primary metabolic-related proteins(24.16%),21 protein synthesis and regulatory proteins(14.09%),13(8.72%)of redox proteins,12(8.05%)of nucleic acid metabolism related proteins,10(6.71%)of secondary metabolite synthesis related proteins,9(6.04%)of polysaccharide metabolic proteins and some other proteins 6(4.03%)respectively;Among all the DEPs,the stimuli response and defense related proteins were the most common types of functional annotations and mainly included oxygen stress related proteins(such as CAT,POD,etc.),JA synthesis,and lipid metabolism related proteins.(such as LOX,OPR3,GDSL,etc.),Pathogen-related related proteins(such as PR10,PR12,PR13,etc.)and other proteins involved in biotic stress and abiotic stress,B.tabaci feeding significantly induced Up-regulated expression of these proteins in susceptible and resistant cultivars.The expression level of some resistant related proteins such as PR 10 and PR13 in resistant cultivars were significantly higher than that of susceptible cultivars.