PLRV-Mediated Physiological Responses,Feeding And Defense Behaviors Of Myzus Persicae

The transmission of insect-vectored viruses entails complex interactions among viruses,host plants and insect vectors.Plant virus infection can alter the characters of host plants or their insect vectors,which can induce changes in the interaction between insects and plants.Virus infection can alter plant morphology,primary and secondary plant compounds,including emitted volatiles and plant nutrients.As well as,fecundity,survival,and behavior are primary traits altered in insect vectors due to virus infection.Numbers of studies hanve indicated that the plant virus can modify the physiological and behavioral characteristics of the insect vectors to enhance the transmission and spread.Plant virus infection may alter both plant morphology and chemistry;therefore,research efforts have focused on the vector’s response to such changes in their plant host.In this paper,the effects of potato leafroll virus(PLRV)infection on the changes of tobacco nutriention and its effect on the life characteristics of Myzus persicae,PLRV-induced tobacco defense response and its mediated effects on the M.persicae,probing behaviour,olfactory behavior variation between PLRV nonviruliferous and viruliferous M.persicae to E-β-farnesene(EβF),and the effects of EβF release on the PLRV transmission efficiency were operated.The main results are as follows:1.PLRV-infected tobacco plants tend to be more attractive to both nonviruliferous and viruliferous M.persicae.The vectors feeding on virus infected plants had greater fecundity,growth rate and more winged aphids emerged than that on virus non-infected plants.The total content of soluble sugar and free amino acids in infected host tobacco were increased significantly than healthy plants.The content of essential amino acids,leucine,lysine,isoleucine,methionine,arginine,threonine,and valine,as well as the non-essential amino acids,proline,tyrosine,alanine and asparagine were significantly increased after PLRV infection.2.The salicylic acid(SA)pathway of host tobacco plant was induced by PLRV infection.The activity of superoxide dismutase(SOD),polyphenol oxidase(PPO)and peroxidase(POD)were significantly increased in viruliferous M.persicae body than those in nonviruliferous aphids.The relative expression of salivary gland gene MP10 in second instar and third instar nymphs,wingless and winged aphids were significantly lower in viruliferous M.persicae compared with that feeding on virus free plants.The relative expression of salivary gland gene MP42 in the third instar and fourth instar nymphs,and the wingless aphid were significantly lower than that without virus infection.3.The olfactory response showed that the nonviruliferous aphids had significant repellent reaction to 10 μL and 100 μL EβF dose,while viruliferous aphids could show the repellent reaction at the 1 μL EβF dose,whih indicated that PLRV-viruliferous aphids were more sensitive to alarm pheromone than nonviruliferous ones.By comparing the relative expression of two EβF-specific binding protein genes OBP3 and OBP7 in M.persicae,we found that the relative expression of OBP7 gene was significantly higher in the fourth instar nymphs,wingless and winged aphids with PLRV viruliferous than that in nonviruliferous.We speculated that the higher relative expression of OBP7 gene might be the major factor prompting the viruliferous aphids more sensitive to EβF.The PLRV transmission efficiency was significantly reduced by EβF release,if the viruliferous aphids feed on tobacco plants for a short period.4.The electrical penetration graph(EPG)technique was employed to monitor the feeding behavioral performance of PLRV viruliferous and nonviruliferous M.persicae on PLRV infected and non-infected tobacco plants.When nonviruliferous M.persicae feeding on PLRV infected plants,the time of penetration difficulties(F wave)were lessened remarkably,the time of watery salivation(E1 wave)and passive ingestion of phloem sap(E2 wave)increased significantly compared with that of M.persicae feeding on healthy plants.When viruliferous M.persicae feeding on PLRV non-infected plants,time of penetration difficulties(F wave)were decreased significantly,time from start of EPG to 1st E were significantly shorter than that of nonviruliferous M.persicae.The relative expression of MPC002 gene in salivary glands of viruliferous apterae and alate M.persicae was significantly higher than that in nonviruliferous M.persicae.