Inverse Effect Of Fungicides On Reproduction Of The Vector Insect The Small Brown Planthopper(SBPH),Laodelphax Striatellus(Fallén),and Its Mechanism

Outbreak of vector insect pests causes more serious damage to crops because they not only injure crops through feeding but also transmit virus diseases.The small brown planthopper(SBPH),Laodelphax striatellus,is a serious vector pest of rice,wheat,and maize,it can transfer from wheat field to rice field.SBPH outbreak occurred in rice in recent years in many provinces in China,and resulted in devastating losses of rice.However,the cause and mechanisms of the outbreak is unknown.The present paper investigated stimulating or suppressing effect of two fungicides,jinggangmycin(JGM)and carbendazim(CBM)on reproduction of SBPH,and their molecular mechanisms.The results are as follows:1.Inverse effect of two fungicides on reproduction of SBPH SBPH is one of the important insect pests of rice,and it is also a pesticide-induced resurgence pest.In this chapter,the effects of two fungicides,JGM and CBM,on the reproduction of SBPH were studied.The results showed that JGM suppressed SBPH reproduction while CBM stimulated the reproduction.In order to explore its causes,we conducted a series of physiological and biochemical and related gene studies.The body weight of JGM-treated females reduced and the body become smaller with shorter oviducts,protein content decreased.There were inverse effects for CBM-treated females.2.Proteomics analysis of SBPH following JGM and CBM treatment A total of 4749 proteins were identified in JGM-treated group,including 95 differential proteins(62 up-regulated,33 down-regulated).And 5828 proteins were identified in CBM-treated group,including 818 differential proteins(452 up-regulated,366 down-regulated).Moreover,we found that there were 3 differential proteins which CBM treatment group showed down-regulated expression while JGM treatment group showed up-regulated expression.In contrast,there were 13 differential proteins which CBM treatment group showed up-regulated expression while JGM treatment group showed down-regulated expression.Among them,the expression of vitellogenin was down-regulated in JGM-treated group while up-regulated in CBM-treated group,which is consistent with reproduction effect induced by two fungicides.In addition,20 differentially expressed proteins were detected in the treatment group(12 up-regulated and 8 down-regulated)in reproductive,reproductive processes,biological regulation,and metabolic processes.In the carbendazim treatment group,Fifty differential proteins were related to reproductive,reproductive processes,biological regulation(24 up-regulated and 26 down-regulated).3:Effects of LCHAD and HSD silencing on reproduction of SBPHThe results of proteomic analysis showed that JGM induced down-regulated expression of long chain-3-hydroxyacyl-CoA dehydrogenase(LCHAD)of SBPH while CBM induced up-regulated expression of hydroxysteroid dehydrogenase-like protein 2-l:ike(HSD).Thus,we silenced the two genes to observe reproduction of SBP through the use of feeding method.The relative expression of LCHAD following silencing LCHAD decreased by 56.7%(Control+ dsLCHAD VS Control)and 58.4%(Control + dsLCHAD VS Control + dsGFP),respectively.The number of eggs laid by SBPH females silenced LCHAD decreased by 53.5%(Control + dsLCHAD VS Control)and 51.6%(Control + dsLCHAD VS Control + dsGFP),respectively.Silenced LCHAD prolonged pre-oviposition period and longevity of females but no significant effect on the oviposition period was observed.Silenced HSD reduced HSD expression by 71.7%(CBM + dsHSD VS CBM + dsGFP)and 72.6%(CBM + dsHSD VS CBM + dsGFP),respectively.(CBM + dsHSD VS CBM)and 72.0%(CBM + dsHSD VS CBM + dsGFP),respectively,the number of eggs laid decreased by 72.8%(CBM + dsHSD VS CBM)and 72.0%(CBM + dsHSD VS CBM+ dsGFP).Silencing HSD reduced oviposition period and longevity of females while no significant effect on pre-oviposition period was observed.Anatomical ovarian showed that LCHAD arnd HSD silencing resulted in the shorted and thinned oviducts of JGM-treated females,with no obvious egg cells.In contrast,oviducts of CBM-treated females thickened and had many yellow banana type egg cells.