在玉米中表达一个截断的ATHB17蛋白增加吐丝时穗重
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作者：Andrea Gallavotti
在植物生长的每一个环节，转录的动态调节是必不可少的。这一般是由转录激活或抑制机制来实现的。最近的证据表明，转录抑制是许多发育和激素的途径采用的一种共同的和普遍的调控机制。同源域亮氨酸拉链II（HD -ZIP Ⅱ）家族的转录因子是一个大家族，其成员是已知的同聚物和异聚物，并调节一系列调控路径。拟南芥ATHB17蛋白携带着一个已知的的抑制基序（EAR基序），在基于原生质体的抑制测定中赋予转录抑制能力。在这项研究中，全长的HD-ZIP II基因ATHB17基因在玉米中超表达，但很快就发现生产了缺乏EAR基序的该蛋白的截断版本。由于这种截短版本保留了同聚和异聚和DNA结合的能力，它促使作者进一步调查它是否可以作为一个玉米内源性HD-ZIP II蛋白的显性负调控。利用原生质体抑制测试，作者显示，通过添加的截断的ATHB17表达构建，他们能够降低玉米的HD -ZIP II蛋白的抑制能力。最后，作者分析了表达拟南芥ATHB17的显性负调控的玉米转基因植株的表型，在重复的田间试验中，发现在营养部分生物保持不变的情况下穗重增加。对这些品系的转录组进行分析，发现穗子的全局转录物水平只有细微的变化。总的来说，这些结果表明研究植物中转录调控机制的重要性。所获得的知识为通过调节转录来提高作物表现提供了新的分子工具。
ATHB17 is a member of the α subclass within the HD-Zip II protein family （From PLoS One）
Expression of a Truncated ATHB17 Protein in Maize Increases Ear Weight at Silking
Abstract: ATHB17 (AT2G01430) is an Arabidopsis gene encoding a member of the α-subclass of the homeodomain leucine zipper class II (HD-Zip II) family of transcription factors. The ATHB17 monomer contains four domains common to all class II HD-Zip proteins: a putative repression domain adjacent to a homeodomain, leucine zipper, and carboxy terminal domain. However, it also possesses a unique N-terminus not present in other members of the family. In this study we demonstrate that the unique 73 amino acid N-terminus is involved in regulation of cellular localization of ATHB17. The ATHB17 protein is shown to function as a transcriptional repressor and an EAR-like motif is identified within the putative repression domain of ATHB17. Transformation of maize with an ATHB17 expression construct leads to the expression of ATHB17Δ113, a truncated protein lacking the first 113 amino acids which encodes a significant portion of the repression domain. Because ATHB17Δ113 lacks the repression domain, the protein cannot directly affect the transcription of its target genes. ATHB17Δ113 can homodimerize, form heterodimers with maize endogenous HD-Zip II proteins, and bind to target DNA sequences; thus, ATHB17Δ113 may interfere with HD-Zip II mediated transcriptional activity via a dominant negative mechanism. We provide evidence that maize HD-Zip II proteins function as transcriptional repressors and that ATHB17Δ113 relieves this HD-Zip II mediated transcriptional repression activity. Expression of ATHB17Δ113 in maize leads to increased ear size at silking and, therefore, may enhance sink potential. We hypothesize that this phenotype could be a result of modulation of endogenous HD-Zip II pathways in maize.
