小米psbA基因5'末端非编码区的结构特征  

Characterization of the 5'-noncoding Region of Millet Chloroplast psbA Gene

作　　者：黄瑶[1] 吴乃虎[1] 

机构地区：[1]中国科学院发育生物学研究所

出　　处：《生物工程学报》1996年第2期119-123,共5页Chinese Journal of Biotechnology

基　　金：国家"863-10l-O7-05"基金

摘　　要：以小米(Setaria italica)为材料,克隆了含有叶绿体psbA基因的2.2kb EcoRⅠ片段,测定了该基因5＇末端非编码区的核苷酸序列。序列分析显示psbA基因5＇末端非编码区存在着与原核类似的启动子结构,其“-10”区的序列为TATACT,与原核生物“-10”共有基序(Consensus motif)仅相差一个核苷酸;其“-35”区的序列为TTGACA,与原核生物“-35”共有基序完全相同。另外,在“-10”区和“-35”区之间还存在着一个类似真核启动子结构的“TATATA”保守序列。这些结果表明小米psbA基因的启动子既具有原核的特征又具有真核的特征。小米psbA基因的mRNA前导序列长87bp,与高粱完全一致,而比水稻多出了“CTATTTT”7个核苷酸,比小麦、大麦和黑麦多出了“TTTT”4个核苷酸。因此推测在禾本科的C_3和C_4植物之间,psbA基因mRNA前导序列区的差异可能具有普遍性。计算机分析结果显示,以上6种植物的psbA基因mRNA前导序列区内均能形成小的茎环结构,而且这段“CTATTTT”额外序列恰好位于茎环结构中,造成了6种植物间茎环大小的差异。这一小的二级结构可能对psbA基因的表达调控有一定的影响。The 2. 2kb EcoR I fragment containing the chloroplast psbA gene from millet (Setaria italica) has been cloned and the nucleotide sequence of the 5'-noncoding region has been determined. The sequence shows that both prokaryote-like and prokary-ote-like promoter structures exit in the 5'-flanking region of psbA. Compared with the consensus sequence of the prokaryotic promoter, only one nucleotide difference is found in the '-10' box TATACT and no difference in the '-35' box TTGACA. Between these two boxes, there is a consensus sequence 'TATATA'. All these results indicate that millet psbA promoter has both prokaryotic and eukaryotic characteristics. The mRNA leader region of millet psbA gene is 87 bp long which is the same as that of the sorghum gene. There is an additional CTATTTT sequence compared with rice and TTTT with wheat, barley and rye genes. So it is presumably universal that this difference exists between C3 and C4 plants in the family of Gramineae. A small stem-loop structure could be found in psbA mRNA leader regions of the above-mentioned six plants by computer analysis. The additional CTATTTT sequence is located in the stem-loop structure, which leads to the different size of the stem-loops of these six species. This small secondary structure may have an effect on the regulation of expression of psbA gene.

关 键 词：小米 PSBA基因 启动子 茎环结构 

分 类 号：S515.032[农业科学—作物学]