The Research On Heterosis Of Molecular Mechanism For Chinese Sea Cucumber,Russian Sea Cucumber And Their Hybrids

Heterosis is important for sea cucumber breeding,but its molecular mechanism remains largely unexplored.In this study,parental lines of Apostichopus japonicus from Russia(R)and China(C)were used to construct hybrids(CR and RC)by reciprocal crossing.We examined the transcriptional profiles of the hybrids(CR and RC)and the purebreds(CC and RR)at different developmental times.A total of 60.27 Gb of clean data was obtained,and 176,649 unigenes were identified,of which 50,312 unigenes were annotated.For small RNA,a total of 202 miRNA were identified,including 7 known-miRNAs and 195 novel-miRNAs.A total of 175 miRNAs were identified as significantly differentially expressed miRNAs(diffmRNA).Besides,a total of 1,097-4,587 differentially expressed genes(DEGs)were identified at 9 month after fertilization.We also found 31 DEGs for GO and NR database,such as fgfs,igfs,megfs and hgfs that were up-regulated in the hybrids(RC and CR).These significant DEGs were mainly involved in the MAPK and FOXO signaling pathways,especially in the Ras-Raf-MEK1/2-ERK module,which may be a key regulator of development and growth in juvenile A.japonicus.These genes may play important roles in heterosis in A.japonicas.Besides,64 DEGs involved in the biosynthesis of saponins were selected,which may affect the development of body wall and immunity between the F1 hybrid and the purebreds.Our study provides fundamental information on the molecular mechanisms underlying heterosis in sea cucumber and might suggest strategies for the selection of rapidly growing strains of sea cucumber in aquaculture.