Transcriptional And Functional Analysis Of Allatostatin-a Gene In The Diamondback Moth Plutella Xylostella

Insect neuropeptides,including a group of polypeptides synthesized,stored and released by the nervous system,are the most diverse group of signal molecules in multicellular organisms.The mature peptides（about 5–80 aa）of most neuropeptides produced by inactive propeptides show the characteristics of low content,high activity and multiple functions,and are involved in almost all behaviors and physiological responses of insects.Alloatostatin-A（AST-A）is widely distributed in insects and mainly presents in the brain,corpus allatum,hemolymph,midgut and ganglion.Previous studies reported that AST-A could affect insect juvenile hormone synthesis,amylase activities,and muscle contraction.The diamondback moth,Plutella xylostella（Lepidoptera:Plutellidae）is an important agricultural pest,of which larva feed on cruciferous plants.Because of its strong reproductive ability,wide host range and strong resistance to pesticides,it is very difficult to control the diamondback moth.Cotesia vestalis（Haliday）（Hymenoptera:Braconidae）,as its dominant endoparasitic wasp,are specialist parasitic wasp of the laval stage of P.xylostella.During the process of parasitism,the wasp injects parasitic factors,such as Cv BV,venom,and teratocytes together with eggs into the host larvae,which are involved in the regulation of the growth and development,digestion,metabolism,immune response and other physiological processes of the host.19 neuropeptide genes from 17 neuropeptide families in the central nervous system（CNS）of P.xylostella were previously identified in our laboratory,but the funtions of these genes were still less known.Therefore,this paper studied the transcription and function of the AST-A gene of P.xylostella（PxAST-A）on the basis of the data available in the laboratory.The results of the study are as follows:1.Identified and characterized mature peptides of PxAST-A,and analyzed the expression level of PxAST-A gene:Based on the genome and transcriptome data of P.xylystella,we cloned and analysed the PxAST-A sequence.According to the mature peptide sequences of AST-A from other insects,the common conservative sequence of 9 mature peptides（Y/FXFGLG）were identified from the propeptides and their C-terminal Gly were amidated.The expression level of PxAST-A was detected by q PCR.The results showed that the expression level of PxAST-A was highest in first instar larvae,and lowest in pupal stage;Among adult,the expression level of PxAST-A in male adults is higher than that in female adults;In tissues,it is significantly highly expressed in the CNS and midgut,showing a tissue-specific distribution.2.The functional study of PxAST-A showed that PxAST-A palyed a role in the growth,development and digestion and metabolism of P.xylostella:The 9C-terminal amidated peptides were synthesized and mixed equally before microinjection.The results showed:（1）In terms of growth and development,the injection of PxAST-A mature pepetides can down-regulate the expression level of ECR genes at the late 4^th instar,and can extend its pupation period;（2）In terms of digestion,it can boost the amylase activity in the midgut of P.xylostella;and（3）In terms of feeding,it can prolong the feeding pause time of P.xylostella.3.The parasitization of C.vestalis can up-regulate the transcriptional expression of PxAST-A and prolong the developmental period:The parasitization of C.vestalis can significantly up-regulate the expression of PxAST-A in the middle and late 4^th instar larva and in the midgut of P.xylostella;The amylase activity was significantly inhibited after parasitism.In addition,Cv BV injection can significantly up-regulat the expression of PxAST-A in the larva and midgut of P.xylostella.And it can also decrease the expression of Ec R and E75 in P.xylostella.Therefore,we proposed that C.vestalis might regulate the expression of host PxAST-A through Cv BV,which interfere the the growth and development of P.xylostella,and decrease its midgut amylase activity.In summary,the study of the transcription and function of PxAST-A in the P.xylostella and impact of parasitism by C.vestalis provides a basis for further research.