小麦淀粉合酶基因家族成员的表达差异分析

Expression Differentiation of Starch Synthase Gene Family Members in Wheat

籽粒淀粉的含量和结构影响小麦的产量和品质,而淀粉合酶在淀粉合成中起着关键作用。植物淀粉合酶基因经多次复制和功能分化,形成了具有不同功能特性的多成员大家族。为揭示淀粉合酶基因家族成员间的序列特性和表达差异,本研究参考已知的水稻淀粉合酶蛋白序列,对小麦全基因组中的淀粉合酶基因进行鉴定,并对其进行差异表达分析。结果共鉴定到27个小麦淀粉合酶基因,这些基因分布在1A/1B/1D、2A/2B/2D、6A/6B/6D、7A/7B/7D染色体上,可分为Group A和Group B两大类,Group A包含TaGBSS、TaSSⅠ、TaSSⅡ三个亚家族,所编码的蛋白均具有motif1~motif10,且motif排列顺序一致;Group B包含TaSSⅢ、TaSSⅣ两个亚家族,所编码的蛋白都缺少motif9和motif10,另外TaSSⅢ亚家族还缺少motif8。与玉米、水稻、高粱、拟南芥不同,小麦淀粉合酶基因没有TaSSⅤ亚家族。同一亚家族内不同基因具有明显的表达差异,其中,TaGBSSⅠ、TaSSⅡa和TaSSⅢa在胚乳中特异表达;小麦相同部分同源群内的淀粉合酶基因间在不同组织和不同发育时期也存在表达差异,TaSSⅡa-B和TaSSⅡa-D在授粉后20 d和30 d的胚乳中表达量比TaSSⅡa-A高。差异表达的淀粉合酶基因启动子中的胚乳特异表达元件(RY-element、AACA-motif和ACGTOSGLUB1)存在类型和数量差异。

The content and structure of grain starch affect the wheat yield and quality.Starch synthase(SS)plays a key role in starch biosynthesis.SS genes are a multi-member family with different functional characteristics,forming by several times of gene duplication and function differentiation.In order to reveal the sequence characteristics and expression differences,the wheat SS genes were identified by referring the known rice SS protein sequences,and differential expression analysis were performed.The result showed that 27 SS genes were identified in wheat,and distributing on chromosomes of 1A/1B/1D,2A/2B/2D,6A/6B/6D,7A/7B/7D.27 SS genes could be divided into Group A and Group B,and Group A contained three subfamilies of TaGBSS,TaSSⅠand TaSSⅡ,all GroupA members had motif1-motif10,and the motif order was consistent;Group B contained two subfamilies of TaSSⅢand TaSSⅣ,both of which lacked motif9 and motif10.In addition,the TaSSⅢsubfamily also lacked motif8.Different from maize,rice,sorghum and Arabidopsis,SS genes of wheat did not contain TaSSⅤsubfamily.There were significant differences in gene expression among different gene copies in the same subfamily,TaGBSSⅠ,TaSSⅡa and TaSSⅢa were specifically expressed in endosperm.SS genes in the same partial homologous group of wheat were also expressed differently in different tissues and at different developmental stages,and the expression levels of TaSSⅡa-B and TaSSⅡa-D were higher than those of TaSSⅡa-A in endosperm at 20 and 30 days after pollination.The type and number of endosperm specific expression elements(RY-element,AACA-motif and ACGTOSGLUB1)in the SS gene promoters were different.