Identification Of I84 Proteases Inhibitor Family In Mollusca And Preliminary Study On Its Function

Protease inhibitors are proteins or small polypeptides ubiquitously present in all organisms,functioning in numerous biological processes.The Family I84 of protease inhibitors in the MEROPS database is a novel protease inhibitor family that has been reported from the eastern oyster Crassostrea virginica and the Chinese razor clam Sinonovacula constricta and is considered to play a role in the host defense of mollusk species.However,there have been few reports systematically describing its distribution.In the present study,analyses of sequence data in public databases did not disclose Family I84 protease inhibitor molecules in non-molluscan animals.Thus,we performed a genome-wide identification of Family I84 homologous genes and analyzed their gene structure,phylogeny in Argopecten irradians,C.gigas,C.virginica,Pecten maximus,S.constricta and Tegillarca granosa.A total of 100 members were identified;4cysteine-rich motifs were detected;and varied gene structure showed high divergence of Family I84.Seven new Family I84 members have been identified from the Asiatic hard clam Meretrix meretrix,the Mediterranean mussel Mytilus galloprovincialis and the Pacific abalone Haliotis discus hannai via c DNA cloning.Measurements of the gene expres SIon in response to salinity stressing and PAMP molecule injections using RT-q PCR generated evidence for the involvements of the identified new family members in host defense of related animals.On the other hand,a comprehensive analysis of available sequence data using a variety of programs and databases did not identify any proteins of non-Molluscan origin that had the molecular attributes allowing them to be assigned as the Family I84 protease inhibitors.Therefore,results of the present research indicated that the Family I84 of protease inhibitors is likely a Mollusca-specific protein family playing a role in the host defense of mollusks uniquely.To our knowledge,it’s the first identification at genome level of Family I84 in bivalves comprehen SIve reference value for the subsequent study of the function.