芡实种仁支链淀粉特性与GeSBE1基因的表达

The Amylopectin Characteristics and the GeSBE1 Gene Expression in Seed Kernels of Euryale ferox Salisb

为探究芡实种仁支链淀粉特性及淀粉分支酶基因(SBE)在支链淀粉合成过程中的作用,以芡实品种‘紫花苏芡’、‘紫花刺芡’为试材,分析种仁发育过程中支链淀粉含量、淀粉粒形成、淀粉糊化特性,并克隆‘紫花苏芡’淀粉分支酶基因(GeSBE1)cDNA全长。结果表明:‘紫花苏芡’种仁的支链淀粉含量及支链淀粉与直链淀粉含量的比值均高于‘紫花刺芡’;‘紫花苏芡’种仁的淀粉粒为不规则多面体、棱角明显、大小较均匀,‘紫花刺芡’种仁淀粉粒多数偏圆、棱角少、大小差异较大;‘紫花苏芡’种仁淀粉较‘紫花刺芡’糊化温度低。GeSBE1 cDNA全长2782 bp,开放阅读框为2466 bp,编码821个氨基酸;该基因的cDNA序列与莲藕SBEI基因的同源性高达78%;种仁发育过程中‘紫花苏芡’GeSBE1的表达量均高于‘紫花刺芡’,表明芡实GeSBE1可能与两品种支链淀粉含量的差异有关。

The amylopectin content, the starch pasting properties and the starch grain structures of the seed kemel of two gordon euryale cultivars of Euryale ferox Salisb, ’Zihua Suqian’ and ’Zihua Ciqian’, were analyzed and a full-length cDNA of the GeSBE1 gene was cloned to characterize the amylopectins in the seed kernel and reveal the role of SBE in the synthesis of amylopectins in the seeds of the two cultivars. It was shown that the amylopectin content and the ratio of amylopectin to amylose content were higher in ’Zihua Suqian’ than in ’Zihua Ciqian’. The starch grains of ’Zihua Su qian’ were mostly irregular polyhedrons with prominent angles, and relatively uniform in sizes. In contrast, the starch grains of ’Zihua Ciqian’ were more or less rounded with much less angles, and more variant in sizes. The starch pasting temperature of the ’Zihua Suqian’ was lower than that of the ’Zihua Ciqian’. The cloned GeSBE1 cDNA was 2782 bp long with an open reading frame of 2466 bp which would encode a peptide of 821 amino acid residues. A sequence comparison showed that the GeSBE1 shared a 78% of homology with the SBEI from Nelumbo nucifera Gaertn. The expression of GeSBE1 in seed kemels of ’Zihua Suqian’ was higher than in those of ’Zihua Ciqian’ during seed kemel development, suggesting that the gene may be responsible for the differences in amylopectin content in the two cultivars.