玉米HD-Zip转录因子基因Zmhdz6的克隆与功能分析

Cloning and Functional Analysis of HD-Zip Transcription Factor Gene Zmhdz6 in Maize

干旱胁迫是限制玉米生长发育和产量形成的主要非生物胁迫因素之一。解析玉米响应干旱的分子机制、挖掘优异的耐旱基因资源,对玉米耐旱种质改良和品种培育具有重要的意义。本研究前期利用耐旱性极端差异的2个玉米自交系,开展了不同水分处理下叶片和根系的转录组测序,通过基因共表达网络分析获得了一个与玉米耐旱相关的重要节点调控基因Zmhdz6,该基因编码一个HD-Zip转录因子。在此基础上,本研究对Zmhdz6的功能进行进一步的研究。在玉米基因组中共有60个HD-Zip转录因子基因,分为4个亚家族;Zmhdz6属于第I亚家族,并与Zmhdz4的序列同源关系较近,Zmhdz4已被报道具有增强耐旱性的功能。干旱和ABA处理下的基因表达分析表明,Zmhdz6的表达受到干旱胁迫和外施ABA处理的诱导,在玉米的叶片和根系中均呈现上调表达。对耐旱性极端差异玉米自交系中Zmhdz6的编码区序列进行测序分析,发现编码区存在5个SNP变异位点,导致编码蛋白中3个氨基酸的差异,但是均不存在于HD或LZ结构域中。Zmhdz6的过表达转基因拟南芥具有显著增强的耐旱性,在干旱胁迫下的存活率高于野生型对照;此外Zmhdz6的过表达转基因拟南芥在正常水分处理下的植株大小显著低于野生型。因此,本研究的结果表明,Zmhdz6是一个重要且有潜力的耐旱基因资源,进一步创制干旱诱导表达Zmhdz6的转基因玉米并评估其育种利用价值,对玉米耐旱改良和分子育种具有重要的意义。

Drought stress is one of the most important constraints affecting maize growth and development and therefore resulting in yield loss. Thus,it is essential to understand molecular mechanisms of drought stress responses in maize and excavate excellent drought-tolerant germplasms and genes for drought tolerance improvement. In our previous studies which based on the transcriptomic comparison of two maize inbred lines with contrasting drought tolerance,a member of HD-Zip transcription factor family,Zmhdz6,was obtained as an important candidate gene for drought tolerance. In the present study,we conducted a functional analysis of Zmhdz6. The phylogenetic analysis of HD-Zip family in maize showed that Zmhdz6 had closer relationship with Zmhdz4,which has proven could improve drought tolerance of transgenic plants. The expression of Zmhdz6 was induced by drought and ABA treatment. The coding sequence of Zmhdz6 in H082183 and Lv28 occurred five SNPs causing three amino acid differences,but all of the SNPs were not in HD or LZ domains. The transgenic Arabidopsis thaliana L. overexpressing Zmhdz6 showed smaller blades,shorter plants and enhanced drought tolerance. These results indicated that Zmhdz6 is an important and potentially valuable gene for the improvement of drought tolerance in maize. Therefore,this study provides theoretical support and genetic resource for droughttolerant maize breeding.