中文摘要：

以玉米籽粒发育特异cDNA文库的表达序列标签（expressedsequencetag，EST）为基础，成功克隆了1条全长碱性螺旋．环一螺旋（basichelix—loop—helix，bHLH）转录因子ZmbHLH5，并对其DNA结构、编码的蛋白质序列和表达进行了分析．结构分析表明，ZmbHLH5的cDNA全长1398bp，具有编码211个氨基酸的开放阅读框（openreadingframe，ORF）区、329bp的3／非翻译区（untranslatedregions，UTR）及433bp的51非翻译区．蛋白序列分析结果表明，ZmbHLH5包含典型的60个氨基酸的bHLH结构域，与其他植物的bHLH转录因子具有很高的同源性（68％-87％）．表达分析结果表明，ZmbHLH5在雌穗和发育早期的籽粒中高丰度表达，并且在籽粒中通过选择性剪接编码至少3种完整蛋白．在原核表达系统中成功诱导表达了融合蛋白GST—ZmbHLH5，其分子量大小为58kD，与预测的蛋白分子量大小一致．

英文摘要：

Based on expressed sequence tags （ESTs） isolated from the cDNA library of maize developing kernels, a full-length putative basic helix-loop-helix （bHLH） transcription factor, named ZrnbHLH5 was cloned successfully. Sequence analysis showed that ZmbHLH5 cDNA was 1 389 bp in length with an open reading frame （ORF） encoding 211 amino acids and untranslated regions （UTR） of 329 and 433 bp at the 3＇ and 5qends, respectively. The protein encoded by ZmbHLH5 had high homology with bHLH transcription factors of other plants, ranging from 68% to 87%, with a conserved 60 amino acids bHLH domain. Expression pattern demonstrated that ZmbHLH5 was expressed at high level in ear and early developing kernels, and at least three ZmbHLH5 isoforms were produced by alternative splicing during kernel development. The fused protein GST-ZmbHLH5 was successfully expressed in prokaryotic expression system with an expected molecular weight of 58 kD.