小麦AGPase4个亚基的克隆及其组织特异性表达

Cloning of Four Subunit Genes for Wheat AGPase and Their Transcript Levels in Different Organs

采用RT-PCR方法从小麦品种豫教2号发育籽粒中克隆出小麦淀粉合成关键酶—AGPase的胞质型小亚基(cytosolic small subunit,SSUⅠ)、质体型小亚基(plastidial small subunit,SSUⅡ)、胞质型大亚基(cy-tosolic large subunit,LSUⅠ)和质体型大亚基(plastidial large subunit,LSUⅡ)的cDNA序列。所克隆的基因cDNA序列长度分别为1 4651、6311、941和535 bp。序列比对结果显示SSUⅠ、LSUⅠ和LSUⅡ与已往报道的大麦、小麦、玉米、水稻等相关基因的同源性较高,而SSUⅡ的cDNA序列为首次克隆,与大麦SSUⅡ相比,5'端缺失编码转移肽的一段序列,表明其可能对质体AGPase活性产生一定影响。通过半定量PCR法发现SSUⅠ与LSUⅠ在籽粒中表达量较高,而SSUⅡ和LSUⅡ在叶片中丰富表达。

cDNA sequences for cytosolic small subunit （SSUⅠ）, plastidial small subunit （SSUⅡ）, cytosolic large subunit （LSUⅠ） and plastidial large subunit （LSUⅡ） of AGPase, the key enzyme of starch synthesis in higher plants, were isolated from grains of Chinese wheat eultivars using RT-PCR. Sequencing showed that the cloned SSUⅠ , LSUⅠ and LSUⅡ were highly identical to the reported genes in GenBank. However, the cloned SSUⅡ lacked a long fragment at 5＇ unique region, different from those in barley, wheat, maize, rice, etc, implying that it could be a novel SSUⅡ. Semi-quantitative PCR indicated that the transcripts of SSUⅠ and LSUⅠ were rich in grains, but SSUⅡ and LSU Ⅱ expressed abundantly in leaves.