Expression Analysis of ISA1 Gene Encoding an Isoamylase-type Starch Debranching Enzyme in Rice

A quantitative real-time PCR(Q-PCR) analysis was performed to investigate the expression pattern of the rice ISA1 gene,encoding an isoamylase-type starch-debranching enzyme,in different tissues as well as in grains at different developmental stages.The results showed that the ISA1 gene was strictly expressed in developing grains.In addition,the 1.1-kb and 2.1-kb promoter region upstream of the start codon of ISA1 gene were cloned and fused with the GUS reporter gene.Then,the GUS chimeric genes were subsequently introduced into rice via Agrobacterium-mediated transformation.The results of both histochemical staining and quantitative analysis of GUS(β-glucuronidase) activity showed that the 2.1-kb ISA1 promoter had an obvious endosperm-specific expression characters,which was consistent with the Q-PCR result of the endogenous gene in rice.However,the 1.1-kb ISA1 promoter presented different expression characters,which drove the GUS reporter gene at a high expression level not only in endosperm but also in culm,culm node and grain hull of transgenic rice.It was speculated that some functional elements which could restrain the expression of target gene in certain organs such as the stem existed in the 2.1 kb promoter.