Studies On The Regulation Of The Exogenous MH And JHA To The Of Silk-fibroin Gene Expression In Silkworm, Bombyx Mori

The growth and development of silkworm are to be regulated directly mainly by meansof the JH which is secreted from corpus allatum and the MH which is secreted formprothoracic gland. The main function of JH in silkworm is to repress the development,metamorphosis and to determine insect states, however the main function of MH is topromote molting, development and metamorphose. The silkgland of silkworm is one kind oftypical organ whose the growth and development are also regulated by the JH and MH. Ourcountry has developed the JHA and MH applying to sericulture production since1970s. Up tonow, we has developed and produced the technology of increasing silk output and promotingsimultaneous mounting. About the mechanization of increasing silk output by exogenoushormone, predecessor developed the wide research on these aspects, including the growth anddevelopment of silkworm, metabolism of amino acid, synthesis of nucleic acid and proteinand cell ultrastructure, but there is very little research form molecular level to study themechanization. In this article, we detected the expression change pattern of4instar and the5instar about the4important gene（Fib-H、Fib-L、Ser-2、Ser-3） using the Sq RT-PCRtechnology and RT-qPCR technology as well as the different dosage of exogenous hormone tothe expression effect of silk protein gene, the main results as below:1Detecting expression of the4silk protein genes（Fib-H、Fib-L、Ser-2、Ser-3）from thebeginning of4thinstar to the4d after5^thmatured silkworm totally11points showed theexpression patterns of Fib-H、Fib-L、Ser-3were similar, on the whole, the expression of thethese genes during the4instar was lower than that during5instar. From the begining of5instar, the expression was gradually going up and reached peak before1d of maturingsilkworm or after2d of maturing silkworm, since then rapidly declined. The expressionpatterns of the two transcripts of Ser-2were similar, the expression of the two transcripts wasrelatively high in the4instar, obviously droped at molting stage and was gradually going upfrom the begining of5instar. The short fragment and the long fragment of Ser-2separatelybegan to decline from the96h and144h of the5^thinstar, since then reached lowest at maturedsilkworm.2. Using different dosage of MH and JHA to treat the different development stages of4th and5^thinstar silkworm, we detected the expression changes of4kinds of silk protein geneswhen they were respectively treated after12h and48h, meanwhile observing the growth anddevelopment. The result showed that the effects of the exogenous MH and JHA to the growthand development of silkworm was very complex, including to the expression of silk proteingenes. Not only the same hormone which was different dosages or at different periods to treatthe silkworms showed the different effects, but also the effects to the silk protein genes weredifferent, there didn’t have unified law. On the one hand, these possibly related to theendogenous hormones’activities at different development stage in silkworm, the expressionstates of silk protein genes as well as feedback regulation of exogenous hormone to endocrinegland; on the other hand, the different silkgand cells in which the different silk protein genesexpress possibly have different reaction to hormones.3According to predecessors’reports about applying MH and JHA to increase the silkproducts’technology, we respectively treated the silkworms at former and middle period of5^thinstar to detect the expression change of Fib-H、Ser-2from the time of hormone treatment tomatured silkworm. The results showed that using the low dosage of MH and JHA to treat theformer and middle period of5^thinstar larvae, the duration of the treatment groups respectivelyprolonged24h and56h, moreover the matured silkworm weight, cocoon shell weight andcocoon layer ratio rose obviously. When using the two dosages of hormone to treat thesilkworm, the expression of Fib-H and Ser-2were rose obviously, and then began to decline.The expression of Fib-H always lower than that of control, especially the JHA treatment ismore obvious; The expression of Ser-2rose significantly on the proxima luce of maturedsilkworm, and exceeded that of control. Therefore, using the MH to treat former period of5^thinstar or using the JHA to treat middle period of5^thinstar, the expression of silk protein canbe promoted in a short time, but the main reason that these methods can increase the silkoutput were prolonging the development duration and increasing the mulberry leafconsupmtion.