缢蛏IGFALS基因的表达特征及IGF系统对生长的调控作用

IGFALS expression characteristics and regulation of IGF system on growth of Sinonovacula constricta

类胰岛素生长因子(insulin-like growth factor,IGF)信号通路在机体的发育、繁殖以及生长等过程中起着重要的调控作用。类胰岛素生长因子酸不稳定亚基(IGF acid-labile subunit,IGFALS)是IGF系统中的重要一员,可通过延长IGF的半衰期参与IGF信号通路的调控。本研究首次在缢蛏转录组数据库中筛选鉴定了两个IGFALS基因,包含完整的开放阅读框,分别命名为IGFALSa和IGFALSb。IGFALSa基因的cDNA序列为4809 bp,编码996个氨基酸;IGFALSb基因的cDNA序列为1925 bp,编码546个氨基酸。在缢蛏不同发育期的表达分析中发现,IGFALSa和IGFALSb在幼虫的前期发育阶段均只有少量表达,而随着幼虫的发育,其表达量逐渐上升;组织表达分析表明,IGFALSa在外套膜和性腺中高表达,IGFALSb则在水管中高表达。利用不同质量浓度胰岛素短期刺激缢蛏稚贝,当质量浓度为10 mg/L时,两个IGFALS基因表达量均显著上调,其下游基因IRS、PDK1、MPKP1的表达量也显著上调;进一步利用10 mg/L胰岛素长期喂养缢蛏稚贝,结果显示其壳长和壳宽的日生长率均显著提升。

Insulin-like growth factor(IGF)signaling pathway plays an important regulatory role in the development,reproduction and growth of the organism.IGF acid-labile subunit(IGFALS)is an important member of the IGF system.After forming a trimer with IGF and IGFBP,IGFALS can extend the half-life of IGF and thus participate in the regulation of IGF system.In this study,two IGFALS genes were firstly screened and identified from the razor clam Sinonovacula constricta transcriptome,including complete ORF,named IGFALSa and IGFALSb.The length of IGFALSa cDNA sequence is 4809 bp,encoding 996 amino acids;The length of cDNA sequence of IGFALSb gene is 1925 bp,encoding 546 amino acids.During the developmental periods,IGFALSa and IGFALSb were only expressed in a small amount in the early developmental stages,and their expression gradually increased with the larval development.In different tissues,IGFALSa was highly expressed,specifically in mantle and gonads.IGFALSb is highly expressed,specifically in siphon.Short-term stimulation to juveniles was performed with different mass concentrations of insulin.When the mass concentration of insulin was 10 mg/L,both IGFALS genes were significantly up-regulated,and the expressions of the downstream genes IRS,PDK1,and MPKP1 were also significantly up-regulated.Further feeding the juvenile with 10 mg/L of insulin for 40 days,the daily growth rates of shell length and shell width were significantly improved.