Plant Research Laboratory, Department of Energy, Michigan State University, East Lansing, MI 48824, USA.
Plant J. 2011 Aug;67(3):395-405. doi: 10.1111/j.1365-313X.2011.04602.x. Epub 2011 May 20.
The evolution of roots and root hairs was a crucial innovation that contributed to the adaptation of plants to a terrestrial environment. Initiation of root hairs involves transcriptional cues that in part determine cell patterning of the root epidermis. Once root hair initiation has occurred, elongation of the root hair takes place. Although many genes have been identified as being involved in root hair development, many contributors remain uncharacterized. In this study we report on the involvement of a member (here dubbed maMYB) of the plant-specific R2R3-MYB family of transcription factors in root hair elongation in Arabidopsis. We show that maMYB is associated with the endoplasmic reticulum membrane with the transcription factor domain exposed to the cytosol, suggesting that it may function as a membrane-tethered transcription factor. We demonstrate that a truncated form of maMYB (maMYB⁸⁴⁻³⁰⁹), which contains the R2R3-MYB transcription factor domain, is localized and retained in the nucleus, where it regulates gene expression. Silencing of maMyb resulted in plants with significantly shorter root hairs but similar root hair density compared with wild type, implying a role of the protein in root hair elongation. 2,4-D (2,4-dichlorophenoxyacetic acid), an exogenous auxin analog that promotes root hair elongation, rescued the short root hair phenotype and maMyb mRNA was induced in the presence of 2,4-D and IAA (indole-3-acetic acid). These results indicate a functional role of maMYB, which is integrated with auxin, in root hair elongation in Arabidopsis.
根和根毛的进化是一个关键的创新，有助于植物适应陆地环境。根毛的起始涉及转录线索，部分决定了根表皮的细胞模式。一旦根毛起始发生，根毛就会伸长。尽管已经确定了许多基因参与根毛发育，但许多贡献者仍未被描述。在这项研究中，我们报告了植物特异性 R2R3-MYB 家族转录因子的一个成员（此处称为 maMYB）在拟南芥根毛伸长中的参与。我们表明，maMYB 与内质网膜相关，转录因子结构域暴露在细胞质中，这表明它可能作为一种膜连接的转录因子发挥作用。我们证明，maMYB 的一种截断形式（maMYB⁸⁴⁻³⁰⁹），包含 R2R3-MYB 转录因子结构域，定位于细胞核并保留在细胞核中，在那里它调节基因表达。maMyb 的沉默导致植物的根毛明显缩短，但与野生型相比根毛密度相似，这意味着该蛋白在根毛伸长中起作用。2,4-D（2,4-二氯苯氧基乙酸）是一种促进根毛伸长的外源性生长素类似物，它挽救了短根毛表型，并且在 2,4-D 和 IAA（吲哚-3-乙酸）存在的情况下诱导 maMyb mRNA。这些结果表明 maMYB 在拟南芥根毛伸长中具有功能作用，它与生长素整合在一起。
