Molecular studies on the formation of calcified hard tissues in marine crustaceans

点击翻译按钮获取中文摘要

This study was carried out to identify mRNAs encoding proteins which regulate formation of the exoskeleton (with particular intesest in the calcification process) in the marine crustacean Penaeus japonicus. For this purpose, mRNAs that were expressed specifically or predominantly at postmolt stages (the exoskeleton becomes calcified at these stages) in cuticular body parts were sought using the differential display and Northern analyzes.In this study, six mRNA species exhibiting the above expression profile were identified, and for four out of the six, cDNA clones isolated. Nucleotide sequences were obtained and analyzed for three mRNA species (named DD-1,4, and 9). DD-1 contained a coding sequence for an asparagine-rich alkaline protein which resembled no known proteins. The conceptual DD-9 protein exhibited sequence similarities to a family of small proteins constituting insect cuticle. DD-4 seemed to encode a proline-rich acidic protein whose sequence was similar to that of the calcium binding protein calphotin. It is of great interest to elucidate the function of the DD-4 protein in the calcification of the crustacean exoskeleton.In this study, a cDNA encoding a putative chitinase (endo-type chitinolytic enzyme) was isolated from cuticular body parts of P.japonicus. This protein was distinct form the chitinases expressed in the digestive organ hepatopancreas.