Identification And Analysis Of ABC Transporter Family In Rice Leaffolder,Cnaphalocrocis Medinalis (Guenée)

The rice leaffolder,Cnaphalocrocis medinalis（Guenée）（Lepidoptera:Pyralidae）,is one of the most important migratory rice pests in China.They have wide distribution range and a number of types of host plants.They have caused great economic losses to agriculture of China in the past half century.At present,all kinds of chemical insecticide are still the main control methods of C.medinalis.However,with the unreasonable use of chemical pesticides for a long time,the sensitivity of C.medinalis to chemical pesticides decreased.ABC transporters（ATP-binding cassette transporters,adenosine triphosphate combined transporter box）is a class of transmembrane protein that uses adenosine triphosphate（ATP）for the inverse concentration gradient transport of substances inside and outside the cell.It has been found that a variety of insects can transport exogenous substances from the inside of the cell to the outside through ABC transporters,that can help to reduce the concentration of intracellular exogenous substances and insecticide susceptibility.In view of the importance of ABC transporter,we identified the ABC transporter family genes of the C.medinalis based on transcriptome sequence data and ABC transporter gene sequence.We determined the expression pattern of ABC transporter in different instars and different parts of intestinal tract by q PCR.The expression pattern of ABC transporter after chemical insecticide stress was studied and analyzed.These results have important theoretical and practical significance for elucidating the structural characteristics and expression pattern of ABC transporter family in the C.medinalis.The main results are as follows:1.Identification and analysis of ABC transporter gene in Cnaphalocrocis medinalisA total of 41 ABC transporter genes were identified by MEGA X,TOPCONS and Model Swiss based on transcriptome data.The genes were divided into 8 subfamilies（A-H）by phylogenetic analysis with reference to the known ABC transporter sequences of Bombyx mori.There were 10 ABCA subfamily genes,6 ABCB subfamily genes,7 ABCC subfamily genes,1 ABCD subfamily gene,1 ABCE subfamily gene,3 ABCF subfamily genes,11 ABCG subfamily genes and 2 ABCH subfamily gene.The relevant ABC transporter information that based on transcriptome data included the protein length range of 66～1855 amino acids,isoelectric point range of 5.14～10.02,and molecular weight range of 7.12～208.67k Da.Meanwhile,the conserved domain structures of 41 ABC transporters were predicted and three-dimensional models were established.2.Expression pattern analysis of ABC transporter genes in different larval instars and different parts of digestive tracts of Cnaphalocrocis medinalisCm UCCR as the reference gene,the relative expression levels of 12 ABC transporter genes,including Cm ABCB5,Cm ABCC1,Cm ABCC4,Cm ABCD1,Cm ABCE1,Cm ABCF1,Cm ABCF2,Cm ABCF3,Cm ABCG1,Cm ABCG2,Cm ABCG3 and Cm ABCG5,in larvae at different instars and different parts of digestive tracts were determined by 2^-△△CT analysis method using q PCR technique.The results showed that the relative expression levels of ABC transporter gene in larvae of different instars were significantly different（P<0.05）.The relative expression levels of 12 genes in the 2nd and 3rd instar larvae were low,and the relative expression levels in the 5th instar larvae were the highest.In addition,in the digestive system,the relative gene expression in the midgut of larvae was significantly higher than that in the foregut and hindgut（P<0.05）.The results show that most ABC transporters genes in the digestive tract of 4th instars larvae are expressed in the midgut,and generally intestine high expression of genes are often related to metabolism of exogenous substances and guidance of resistance formation.Therefore we can speculate that maybe ABC transporters of C.medinalis larvae is related to its detoxification metabolism and the formation of resistance.3.Expression pattern analysis of ABC transporter genes in Cnaphalocrocis medinalis under insecticide stressCm UCCR was used as reference gene and 2^-△△CT analysis method was used by q PCR technique.The relative expression levels of 12 ABC transporter genes such as Cm ABCB5,Cm ABCC1,Cm ABCC4,Cm ABCD1,Cm ABCE1,Cm ABCF1,Cm ABCF2,Cm ABCF3,Cm ABCG1,Cm ABCG2,Cm ABCG3 and Cm ABCG5 were determined and analyzed under the stress of three insecticides（chlorantraniliprole,emamectin benzoate and avermectin）The results showed that the relative expression levels of ABC transporter genes in larvae under some insecticide stress treatments had significant changes（P<0.05）.The relative expression levels of each gene in the chlorantraniliprole treatment group were significantly increased compared with the control group（P<0.05）,while there were no significant differences between the emamectin benzoate treatment group and the control group,and between the avermectin treatment group and the control group.Some insecticide treatments significantly affected the expression of ABC transporter gene in rice leaf roller larvae.Therefore,we hypothesized that ABC transporter may be related to detoxification metabolism in the C.medinalis.