过表达TaHDZipI-5基因增强小麦的耐冷和抗旱性

      评价胁迫相关基因的功能特性有助于阐明植物响应环境因子的机制。近日，澳大利亚阿德莱德大学的研究人员证实了编码胁迫响应亮氨酸同源域拉链I类转录因子的TaHDZipI-5基因在小麦应对冷害和干旱胁迫过程中发挥重要作用。研究结果发现，低温能够显著诱导TaHDZipI-5基因的表达，当胁迫消失时，该基因在花和发育早期的籽粒中仍保持高表达活性，表明TaHDZipI-5基因参与开花期冷害的耐性调控。酵母单杂交试验结果表明，TaHDZipI-5的激活结构域在C端，蛋白分子3D结构的分析发现，TaHDZipI-5蛋白的同源二聚体、TaHDZipI-5蛋白与TaHDZipI-3蛋白的异源二聚体与DNA的相互作用存在差异。最后该研究发现，组成型过表达TaHDZipI-5基因的转基因普通小麦响应冷害和干旱胁迫的耐性显著增强，然而，转基因株系出现株高和生物量变小、花期延长和产量降低等非预期的植株表型；而通过利用胁迫诱导型启动子试图改善转基因小麦植物表型的尝试并未获得预期的效果，表明TaHDZipI-5基因的表达具有严格的组织空间要求。
Plant Biotechnology Journal,  28 November 2017
Overexpression of the class I homeodomain transcription factor TaHDZipI-5 increases drought and frost tolerance in transgenic wheat
Authors
Yunfei Yang,Sukanya Luang,John Harris,Matteo Riboni,Yuan Li,Natalia Bazanova,Maria Hrmova,
Stephan Haefele,Nataliya Kovalchuk,Sergiy Lopato
Summary
Characterisation of the function of stress-related genes helps to define mechanisms of plant responses to environmental conditions. The findings of this work defined the role of the wheat TaHDZipI-5 gene, encoding a stress-responsive homeodomain-leucine zipper class I (HD-Zip I) transcription factor, during the development of plant tolerance to frost and drought. Strong induction of TaHDZipI-5 expression by low temperatures, and the elevated TaHDZipI-5 levels of expression in flowers and early developing grains in the absence of stress, suggest that TaHDZipI-5 is involved in the regulation of frost tolerance at flowering. In the absence of stress, TaHDZipI-5 was expressed in The TaHDZipI-5 protein behaved as an activator in a yeast trans-activation assay, and the TaHDZipI-5 activation domain was localised to its C-terminus. The TaHDZipI-5 protein homo- and hetero-dimerises with related TaHDZipI-3, and differences between DNA interactions in both dimers were specified at 3D molecular levels.The constitutive overexpression of TaHDZipI-5 in bread wheat significantly enhanced frost and drought tolerance of transgenic wheat lines with the appearance of undesired phenotypic features, which included a reduced plant size and biomass, delayed flowering and a grain yield decrease. An attempt to improve the phenotype of transgenic wheat by the application of stress-inducible promoters with contrasting properties did not lead to the elimination of undesired phenotype, apparently due to strict spatial requirements for TaHDZipI-5 overexpression.