Research in expression differences of bre-3 and bre-5 mRNA in Plutella xylostella susceptible and resistant to Cry1Ac

DBM1Ac-R strain of Plutella xylostella was selected with Cry1Ac in laboratory and showed 356-fold resistance to Cry1Ac compared with a susceptible strain (DBM1Ac-S).The relative expression of synthetase gene of Glycosphingolipid(GSLs) bre-3 and bre-5 mRNA of DBM1Ac-S and DBM1Ac-R strains were determined using real-time qPCR,from 2nd-instar to mature larvae,pupa and midgut of 4th-instar.The results showed that both bre-3 and bre-5 mRNA were found to express in different development stages and midgut;The relative expression of bre-3 mRNA in DBM1Ac-S strain was significant higher than DBM1Ac-R strain,exhibiting 2.36,5.54 and 2.68 times in 3th-instar,4th-instar and mature larvae respectively;The relative expression of bre-5 mRNA in DBM1Ac-S strain were 1.19,3.13,1.78,1.75 and 1.65 times respectively compared with DBM1Ac-R strain from 2th-instar to mature larvae.The results suggested that there may be a correlation between the lower relative expression of bre-3 and bre-5 mRNA in DBM1Ac-R from 3th to mature larvae and the long-term Cry1Ac toxin selection to DBM1Ac-R strain.In the same stage of DBM1Ac-S and DBM1Ac-R strains,the mRNA level expression of bre-5 was higher than bre-3,showing obvious advantage of gene expression.These findings will provide important basis for further study on GSLs,one of the receptors of Bacillus thuringiensis crystal proteins.