| Sitotroga cerealella Olivier is a serious stored grain pest in the world.Now the chemical control against the moth is the major method.But as the problem of “3R” becomes more and more serious,it is extremely urgent to select a safe and effective environment-friendly pesticide.Many studies have indicated that botanical pesticides possess the characteristics of low toxicity,friendly environment,wide insecticidal spectrum,and more targets,which can solve the problem of “3R” effectively we are facing now.The early research in our laboratory found the major component of garlic essential oil diallyl trisulfide possesses the characteristics to interfere with mating behavior of Sitotroga cerealella.Meanwhile,the result of transcriptome also showed it can regulate the transcriptional level of many genes related with the moth reproduction treated with sub lethal dose.In order to clarify the mechanism of diallyl trisulfide on reproduction against Sitotroga cerealella,this study will research effects of diallyl trisulfide on the moth’s development of ovary,oogenesis,fecundity,and chorion gene expression.The main results are as followed :1.The influence of diallyl trisulfide on development of ovarian tube against females Sitotroga cerealella.The ovaries were dissected from the females newly,6h,12 h,and 24 h after emergence,respectively;And the different developmental stages were observed with anatomical lens.The results indicated there were follicles at different developmental stages in ovarian tubules.The ovarian tubules were shorter,the quantity and volume of eggs were less at newly emergence.And then the ovarian tubules became longer and longer,the quantity and volume of eggs were more with time increasing.However,the ovary development treated with diallyl trisulfide was restrained remarkably at 6 h,12 h,and 24 h after fumigation by.The length of ovarian tubules was inhibited significantly compared with that of contrast,and the numbers of follicle in ovarian tube were less than that of contrasts,in addition,the size of the egg chamber located with the base of ovary was also restrained.2.The influence of diallyl trisulfide on ovary developmental ultrastructure of Sitotroga cerealella.Females Sitotroga cerealella were fumigated 6 h after emergence treated with diallyl trisulfide for 7 h,dissected,and then the developmental ultrastructure of ovaries was observed by transmission electron microscopy.The results showed that morphological features of follicles in ovarioles were changed much.For the contrasts,the follicular microvilli of ovary at the base of tube has disappeared,showing it was at the period of egg-shell formation.However,for the groups treated with diallyl trisulfide,those were easily visible,which means it was just at the late stage of egg yolk accumulation.There were many large yolk granules accumalated in the follicular oocytes located in the end of ovarian tube in contrasts,while smaller in that of groups treated with diallyl trisulfide showing development was slowercompared with contrasts.The morphological features of ovarian follicles have no significantdifference between contrasts and treatment groups in central tube.The Sitotroga cerealella after emergence 6 h,were fumigated for 24 h by diallyl trisulfode,using electron microscope observed the ovary.The results indicated three parts of the follicle structure were formed eggshell,there was no significant difference between the control and the treatment group.Therefore,the fumigation by diallyl trisulfode can inhibit the ovary of Sitotroga cerealella developmental speed,but can not prevent the oogenesis of Sitotroga cerealella.3.The influence of diallyl trisulfide on fecundity against females Sitotroga cerealella.The females Sitotroga cerealella were fumigated 6 h and the results showed the numbers of eggs laid,the eggs left in moths,and the number of eggs pregnanted per female were no significantly different(P>0.05).However,the eggs laid were decreased obviously,and the eggs left in body were higher than that of contrasts when femaleswere treated 12 h and 24 h after fumigation,which indicated diallyl trisulfide possesses the ability to inhibit ovipositon and the process of egg production.4.The influence of diallyl trisulfide on expression of three chorion genes against females Sitotroga cerealella.The primers of three chorion genes of Sitotroga cerealella were designed from the transcriptome library and the full-length gene sequence of three chorion genes were cloned respectively.The results showed the open reading-fragment of gene S.cerealella Chorion 191 was 438 bp,encoded 145 amino acids,molecular weight predicted was 14.7kDa,and isoelectric point was 4.9;the open reading-fragment of gene S.cerealella Chorion 668 was 555 bp,encoded 185 amino acids,molecular weight predicted was 17.1kDa,and isoelectric point was 4.9;the open reading-fragment of gene S.cerealella Chorion 7774 was 564 bp,encoded 188 amino acids,molecular weight predicted was 17.4kDa,and isoelectric point was 4.4.The expression profiles of the three chorion genes were similar,and the expression signals were observed at the pupal stage.The transcriptional level of the three chorion genes was significantly increased at 6h after emergence,and reached the highest level at 12 h after emergence,and then decreased with time increasing.The expression of S.cerealella Chorion 191,S.cerealella Chorion 668,and S.cerealella Chorion 7774 of the female 6 h after emergence did not change significantly 7 h after fumigation by diallyl trisulfide compared with that of contrasts.In a word,all the research work will help us to know the mechanism of diallyl trisulfide on the reproduction control against females S.cerealella.diallyl trisulfide possesses the characteristics to inhibit ovarian development,oogenesis development,decrease the capability to lay egg,all which results in oviposition inhibition.These results will lay a foundation for the further study on the molecular mechanism of diallyl trisulfide on reproductive control against Sitotroga cerealella,and also find a new target and a new idea for controlling these pests. |
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