title: Polymorphism in a serine protease inhibitor gene and its association with the resistance of bay scallop (Argopecten irradians) to Listonella anguillarum challenge.
abstract: Serine protease inhibitors (SPIs) play a crucial role in regulation of both host and bacterial serine protease. They are classified into several protein families, where Kazal-type inhibitors are one of families with multi-domain. In the present study, the polymorphism of AiSPI from Bay scallop Argopecten irradians was found to be associated with disease resistance of bay scallop against Listonella anguillarum. Nine single nucleotide polymorphisms (SNPs) were identified in the exon region of AiSPI, where five SNPs were non-synonymous mutation. Three of these mutations were located in "kazal-like 3"domain, two SNP loci positioned at +536, +1312 were selected for further association studies. For the locus +536, the genotype frequency of A/G in the resistant stock (12.8%) was significantly lower (p < 0.05) than that in the susceptible stock (35.1%), while, the genotype A/A in the resistant stock (87.2%) was significantly higher in comparison with susceptible stock (64.9%) (p < 0.05). The G allele frequencies were 6.4% and 17.6% in resistant stock and susceptible stock, respectively, and χ2-test revealed a significant difference in the frequency distribution between the two stocks (p < 0.05). But there was no significant association between the mutation C-T at locus +1312 with either resistant or susceptible group (p > 0.05). The genotype frequencies of T/T, T/C, C/C at locus +1312 were 94.6%, 2.7% and 2.7% respectively in the susceptible stock, while 100%, 0% and 0% respectively in the resistant stock. The amino acid change for the mutation at locus +536 A-G was from asparagine to serine, and the predicted homology model of this amino acid variation could affect its function as well as the structural integrity of the domain. In vitro elastase inhibition assay of the protein variants at locus +536 was conducted to explicate the effect of SNP. The increasing concentration of protein (0 mmol/L- 2.93 mmol/L) was incubated with 80 nmol/L elastase where the residual enzyme activity values for rAiSPI (N) with A variant and rAiSPI (S) with G variant were started to reduce from 0.40 to 0.215 and 0.435 to 0.356, respectively. The elastase inhibition ability of rAiSPI (N) variant was significantly higher than that of rAiSPI (S) (p < 0.01). The results suggested that the mutation at locus +536A/A significantly associated with disease resistance of bay scallop would shed light for selective breeding program.
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China; Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Centre for Climate Change Studies, Sathyabama University, Jeppiaar Nagar, Rajiv Gandhi Salai, Solinganallur, Chennai, Tamil Nadu 600 119, India.
authors.forename: Vinu S
authors.initials: VS
authors.lastname: Siva
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China.
authors.forename: Lingling
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Limei
authors.initials: L
authors.lastname: Qiu
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.
authors.forename: Jialong
authors.initials: J
authors.lastname: Yang
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China.
authors.forename: Chuanyan
authors.initials: C
authors.lastname: Yang
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian 116023, China. Electronic address: lshsong@dlou.edu.cn.
authors.forename: Linsheng
authors.initials: L
authors.lastname: Song
mesh_terms: D000818:Animals; D001483:Base Sequence; D007113:Immunity, Innate / Q000235:genetics*; D053526:Listonella / Q000276:immunology / Q000502:physiology*; D009154:Mutation; D049897:Pectinidae / Q000235:genetics* / Q000276:immunology* / Q000382:microbiology; D020641:Polymorphism, Single Nucleotide; D015842:Serine Proteinase Inhibitors / Q000235:genetics* / Q000378:metabolism
chemical_list: D015842:Serine Proteinase Inhibitors
keywords: Argopecten irradians; Bay scallop; Disease resistance; Disease susceptibility; Serine protease inhibitor; Single nucleotide polymorphism