Genome-Wide Analysis of the Cyclin-Dependent Kinases(CDK)and Cyclin Family in Molluscs

Cell cycle regulation that plays a pivotal role during organism growth and development is primarily driven by cyclindependent kinases(CDKs)and Cyclins.Although CDK and Cyclin genes have been characterized in some animals,the studies of CDK and Cyclin families in molluscs,the ancient bilaterian groups with high morphological diversity,is still in its infancy.In this study,we identified and characterized 95 CDK genes and 114 Cyclin genes in seven representative species of molluscs,including Octopus bimaculoides,Pomacea canaliculata,Biomphalaria glabrata,Lottia gigantea,Mizuhopecten yessoensis,Crassostrea gigas and Aplysia californica.Genes in CDK and Cyclin families were grouped into eight and 15 subfamilies by phylogenetic analysis,respectively.It should be noted that duplication of CDK9 gene was detected in P.canaliculate,L.gigantea and M.yessoensis genomes,which has never been recorded in animals.It is speculated that duplication may be the main course of expansion of the CDK9 subfamily in the three molluscs,which also sheds new light on the function of CDK9.In addition,Cyclin B is the largest subfamily among the Cyclin family in the seven molluscs,with the average of three genes.Our findings are helpful in better understanding CDK and Cyclin function and evolution in molluscs.