Expression Patterns And Functions Of EcR And USP In Larvae Of Spodoptera Exigua

Spodoptera exigua is an important polyphagous and worldwide distribution agricultural pest, which continues to expand the occurrence regions in our country, and the degree become increasingly serious. In order to prevent and control beet armyworm, we still mainly used chemical control.But, nowadays beet armyworm resistance monitoring shows that the development of pesticide resistance gose very quickly, the effects of conventional chemical pesticides, such as organophosphate and pyrethroid pesticides, are far from ideal. It is difficult to effectively control the beet armyworm outbreak, we must look for other control methods. And ecosystems issues caused by chemical control, gained much-debated urgently, we have to develop new type of pest control means and manners. Complete metamorphosis insects in order to complete the entire life cycle should go through periodic larval molting and metamorphosis, the physiological activities of insect development have been completed successfully in the fine under the control of a series of hormones EcR and USP are on the starting position of the cascade regulation of insect development, such as metamorphosis and reproduction process, with organization and time-specific. EcR and USP have been found in a variety of insects and arthropods. There must be more comprehensive descriptions of the structures and features of EcR and USP in the different insects, so as to have a deeper understanding of their modes of action and lay a foundation for future study. And nomatter the regulation of growth and development and the reproduction of the beneficial insects or pest prevention research both have the very important practical value and the theoretical value. Despite rapidly increase of research on the insect EcR and USP in recent years, most of them focused on the EcR and USP gene function in the ecdysone-mediated signal transduction pathway and molecular mechanism of hormone regulated gene expression, all of them made important research progress. But interaction relationship between the metamorphosis-related genes, each gene play different function in insect growth and development at different time points, the JH receptor and so on, are yet to be elucidated. Still it is far from a detailed mechanism, to clarify insect molting and metamorphosis.EcR and USP gene of beet armyworm were studied in a combination way. Firstly the expression patterns of EcR and USP genes as well as EcR-A and EcR-B genes in the4th instar and5th instar larvae of beet armyworm were researched, there we used real-time quantitative PCR. Secondly EcR and USP functions were researched using RNAi technology. The results showed that the USP gene mRNA expression level in the4th instar larvae was significantly higher than the expression level of5th instar. The EcR gene mRNA expression level of5th instar larvae was significantly higher than the expression level of4th instar. EcR and USP gene mRNA expression levels in the later stage of each instar were significantly greater than the initial stage of each instar. The mRNA expression trends of EcRA and EcRB genes in the4th instar were basically the same. EcRA and EcRB were synchronized expression of the first peak in the early fifth instar also. Expression differences appeared in the final stage of fifth instar before pupation. The EcRA in the fifth instar at84h before the EcRB mRNA expression appeared second expression peak, but EcRB appeared the second expression peak at HSC. After RNAi Spodoptera exigua larvae had abnormal growth and development as well as phenotypic defects phenomenon. dsRNA treated-larvae obviously, they were difficult to complete the larva-larvae molting process, and the larvae-pupae metamorphosis process, and caused a different proportion of lethal phenotype, as well as EcR and USP gene transcript expression levels were reduced.Analysis of EcR and USP genes expression patterns about different instars larvae of beet armyworm:Illustrating expression patterns of EcR and USP genes were basic synchronization, that is, the EcR and USP genes have high expression levels in the late period of every instar, and USP before EcR appeared expression peaks in each instar, which maybe resulted from the USP before the EcR exercise biological functions. But there still existed differences between EcR expression pattern and USP xpression pattern. Specifically USP with a high expression in the4th instar, EcR with a high expression in the5th instar, this unsynchronized expression patterns may be due to that the EcR and USP may form heterodimers respectively with other nuclear receptors and to exercise physiological functions. Showing that the EcR-A and EcR-B in larvae-larvae molt process with the same expression pattern, but the difference of expression is generated in the final period of fifth instar before larvae-pupae metamorphosis, probably due to the EcR-A and EcR-B play different roles involved in different physiological functions during metamorphosis-EcR and USP gene play key role in the larvae-larvae, larvae-pupae metamorphosis.