Maes Lies, Inzé Dirk, Goossens Alain
Department of Plant Systems Biology, Flanders Institute for Biotechnology, Ghent University, 9052 Ghent, Belgium.
Plant Physiol. 2008 Nov;148(3):1453-64. doi: 10.1104/pp.108.125385. Epub 2008 Sep 10.
Trichome initiation in Arabidopsis (Arabidopsis thaliana) is controlled by the TRANSPARENT TESTA GLABRA1 (TTG1) network that consists of R2R3- and R1-type MYB-related transcription factors, basic helix-loop-helix (bHLH) proteins, and the WD40 protein TTG1. An experimental method was designed to investigate the molecular mechanisms by which jasmonates, cytokinins, and gibberellins modulate Arabidopsis leaf trichome formation. All three phytohormones provoked a seemingly common effect on cell patterning by promoting trichome initiation but caused strikingly distinct effects on cell and trichome maturation. The phytohormonal control was mediated by transcriptional regulation of the established TTG1 complex and depended on the R2R3-MYB factor GLABRA1. However, unsuspected degrees of functional specialization of the bHLH factors and a resultant differential molecular regulation of trichome initiation on leaf lamina and leaf margins were revealed. Trichome formation on leaf lamina relied entirely on GLABRA3 and ENHANCER OF GLABRA3. Conversely, TRANSPARENT TESTA8 (TT8) was particularly important for marginal trichome development. This hitherto unknown role for TT8 in trichome formation further underscored the functional redundancy between the three TTG1-dependent bHLH proteins.
拟南芥（Arabidopsis thaliana）表皮毛的起始受透明种皮光滑1（TRANSPARENT TESTA GLABRA1，TTG1）网络控制，该网络由R2R3型和R1型MYB相关转录因子、碱性螺旋-环-螺旋（basic helix-loop-helix，bHLH）蛋白以及WD40蛋白TTG1组成。设计了一种实验方法来研究茉莉酸、细胞分裂素和赤霉素调节拟南芥叶片表皮毛形成的分子机制。所有这三种植物激素通过促进表皮毛起始对细胞模式产生了看似共同的影响，但对细胞和表皮毛成熟产生了显著不同的影响。植物激素的控制是由已建立的TTG1复合体的转录调控介导的，并且依赖于R2R3-MYB因子GLABRA1。然而，研究揭示了bHLH因子意想不到的功能特化程度以及由此导致的叶片和叶缘表皮毛起始的差异分子调控。叶片上表皮毛的形成完全依赖于GLABRA3和GLABRA3增强子。相反，透明种皮8（TRANSPARENT TESTA8，TT8）对边缘表皮毛的发育尤为重要。TT8在表皮毛形成中迄今未知的作用进一步强调了三种依赖TTG1的bHLH蛋白之间的功能冗余。
