State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China.
J Integr Plant Biol. 2012 Oct;54(10):729-37. doi: 10.1111/j.1744-7909.2012.01159.x.
Recent plant development studies have identified regulatory pathways for epidermal cell differentiation in Arabidopsis thaliana. Interestingly, some of such pathways contain transcriptional networks with a common structure in which the homeobox gene GLABLA2 (GL2) is downstream of the transactivation complex consisting of MYB, bHLH, and WD40 proteins. Here, we review the role of GL2 as an output device of the conserved network, and update the knowledge of epidermal cell differentiation pathways downstream of GL2. Despite the consistent position of GL2 within the network, its role in epidermal tissues varies; in the root epidermis, GL2 promotes non-hair cell differentiation after cell pattern formation, whereas in the leaf epidermis, it is likely to be involved in both pattern formation and differentiation of trichomes. GL2 expression levels act as quantitative factors for initiation of cell differentiation in the root and leaf epidermis; the quantity of hairless cells in non-root hair cell files is reduced by gl2 mutations in a semi-dominant manner, and entopically additive expression of GL2 and a heterozygous gl2 mutation increase and decrease the number of trichomes, respectively. Although few direct target genes have been identified, evidence from genetic and expression analyses suggests that GL2 directly regulates genes with various hierarchies in epidermal cell differentiation pathways.
最近的植物发育研究已经确定了拟南芥表皮细胞分化的调控途径。有趣的是，这些途径中的一些包含具有共同结构的转录网络，其中同源盒基因 GLABLA2(GL2)位于由 MYB、bHLH 和 WD40 蛋白组成的转录激活复合物的下游。在这里，我们回顾了 GL2 作为保守网络输出设备的作用，并更新了 GL2 下游表皮细胞分化途径的知识。尽管 GL2 在网络中的位置一致，但它在表皮组织中的作用不同；在根表皮中，GL2 促进细胞模式形成后非毛细胞的分化，而在叶表皮中，它可能参与毛状体的形成和分化。GL2 表达水平作为根和叶表皮细胞分化起始的定量因素；gl2 突变以半显性方式减少非根毛细胞文件中无毛细胞的数量，并且 GL2 的异位累加表达和杂合 gl2 突变分别增加和减少毛状体的数量。尽管已经鉴定出少数直接靶基因，但来自遗传和表达分析的证据表明，GL2 直接调控表皮细胞分化途径中具有各种层次结构的基因。
