Effect Of Rice Volatiles Induced By Insect Pest On The Oviposition Of Chilo Suppressalis

The rice stem borer,Chilo suppressalis(Walker),poses a major threat to rice production in many Eurasian countries such as China and Japan.It primarily occurs in the Yangtze River basin and the southern rice-producing areas of China,with its larvae causing damage to the rice neck.Effective population control of C.suppressalis and reducing the resulting loss of rice yield is a pressing issue in rice production.During the preliminary test,it was observed that 2-heptanol had a suppressive effect on the oviposition of female C.suppressalis moths,whereas α-cedarene had a stimulating effect.Subsequently,the potential mechanism underlying the impact of these two volatiles on the reproduction of C.suppressalis was investigated through the expression of genes related to the physiological development of insects and the intestinal microflora.This study provides a reference for the development of green control technology for C.suppressalis based on oviposition regulation.The main findings are as follows:1.After testing different concentrations of 2-heptanol and examining the effect ofα-cedarene on egg production in C.suppressalis females,it was found that at concentrations of 0.1 μg/μl and 1 μg/μl,2-heptanol suppressed the egg production of female moths,with the most significant inhibition observed at 0.1 μg/μl(P<0.01).On the other hand,α-cedarene significantly stimulated egg production in female C.suppressalis moths at a concentration of 10 μg/μl(P<0.01).2.The expression dynamics of vitellogenin(Vg)and early response gene Krüppel homolog 1(Kr-h1)of juvenile hormone(JH)in C.suppressalis that exposed to two volatiles were determined.The results show that,The expression level of Kr-h1 gene in ovaries of female moths exposed to α-cedarone was significantly higher than that in the n-hexane control group,and the expression level of Kr-h1 gene in adipose bodies was significantly higher than that in the 2-heptanol treatment group;After exposure to two volatiles,the expression of Vg gene in female moth ovaries significantly decreased in a short period of time,but there was no significant difference between the female moth ovaries and the n-hexane control group at 36 hours.The expression level of Vg gene in adipose tissue was significantly decreased at 24 hours and 36 hours,respectively,and there was no significant difference between the female moth ovaries and the control group at other time points3.The results of high-throughput transcriptome sequencing showed that the reproductive-related pathway genes were significantly up-regulated in female C.suppressalis moths when it was exposed to α-cedarene for 12 h and 36 h,and the q PCR confirmed this result.The results also showed that key genes in pathways related to insect stress resistance,hormone precursors,and detoxification enzymes were significantly up-regulated.When the pest was exposed to 2-heptanol for 12 h,the immune-related pathway genes,particularly the genes in the immune pathways induced by bacteria,were significantly up-regulated in female C.suppressalis moths.Detoxification enzyme-related genes were also significantly up-regulated,while key genes in the protein ubiquitination pathway were significantly down-regulated.4.Based on the transcriptome sequencing results,we further studied the dynamic changes of gut microbial community in female C.suppressalis exposed to 2-heptanol.The 16 S amplicon sequencing results showed that after 12 h of exposure to 2-heptanol,the abundance of gut microbial community in female C.suppressalis was significantly reduced.Among them,the relative abundance of two microbial taxa,Enterococcus and Pantobacterium,was significantly lower than that in other treatments.Further studies are needed to investigate whether these two microbes are involved in regulating the egg production of C.suppressalis.In summary,exposure to α-cedarene led to upregulation of reproductive-related pathways genes in female C.suppressalis moth,with significant increases the expression level of Vg and Kr-h1,which may be the potential mechanism to promote the oviposition of the female moth.In contrast,exposure to 2-heptanol initially upregulated the immune-stimulating pathway in female moths at the early stage,but caused downregulation of genes related to protein ubiquitination at the later stage,and decreased the abundance of immune bacterial communities in the female moth body,which may be one of the reasons for the suppression in oviposition of female moths.However,the molecular mechanisms underlying the effects of these two rice volatiles on female C.suppressalis oviposition require further investigation.