Epidermal cell fate determination—including trichome initiation, root hair formation, and flavonoid and mucilage biosynthesis in Arabidopsis (Arabidopsis thaliana)—are controlled by a similar transcriptional regulatory network. In the network, it has been proposed that the MYB-bHLH-WD40 (MBW) activator complexes formed by an R2R3 MYB transcription factor, a bHLH transcription factor and the WD40-repeat protein TRANSPARENT TESTA GLABRA1 (TTG1) regulate the expression of downstream genes required for cell fate determination, flavonoid or mucilage biosynthesis, respectively. In epidermal cell fate determination and mucilage biosynthesis, the MBW activator complexes activate the expression of GLABRA2 (GL2). GL2 is a homeodomain transcription factor that promotes trichome initiation in shoots, mucilage biosynthesis in seeds, and inhibits root hair formation in roots. The MBW activator complexes also activate several R3 MYB genes. The R3 MYB proteins, in turn, competing with the R2R3 MYBs for binding bHLH transcription factors, therefore inhibiting the formation of the MBW activator complexes, lead to the inhibition of trichome initiation in shoots, and promotion of root hair formation in roots. In flavonoid biosynthesis, the MBW activator complexes activate the expression of the late biosynthesis genes in the flavonoid pathway, resulting in the production of anthocyanins or proanthocyanidins. Research progress in recent years suggests that the transcriptional regulatory network that controls epidermal cell fate determination and anthocyanin biosynthesis in Arabidopsis is far more complicated than previously thought. In particular, more regulators of GL2 have been identified, and GL2 has been shown to be involved in the regulation of anthocyanin biosynthesis. This review focuses on the research progress on the regulation of GL2 expression, and the roles of GL2 in the regulation of epidermal cell fate determination and anthocyanin biosynthesis in Arabidopsis.

中文翻译：

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GLABRA2，一种拟南芥表皮细胞命运测定和花色苷生物合成的常用调节剂

表皮细胞命运的确定-包括拟南芥（Arabidopsis thaliana）中的毛状体起始，根毛形成以及类黄酮和粘液的生物合成-由类似的转录调控网络控制。在网络中，有人提出由R2R3 MYB转录因子，bHLH转录因子和WD40重复蛋白TRANSPARENT TESTA GLABRA1（TTG1）形成的MYB-bHLH-WD40（MBW）激活物复合物调节下游基因的表达。细胞命运测定，类黄酮或粘液生物合成所必需的。在表皮细胞命运测定和粘液生物合成中，MBW激活物复合物激活GLABRA2（GL2）的表达。GL2是一个同源域转录因子，可促进芽中的毛状体起始，种子中的粘液生物合成，并抑制根中的根毛形成。MBW激活物复合物还激活了多个R3 MYB基因。R3 MYB蛋白又与R2R3 MYB竞争结合bHLH转录因子，因此抑制了MBW激活剂复合物的形成，导致了芽中毛状体起始的抑制，并促进了根中根毛的形成。在类黄酮生物合成中，MBW激活物复合物激活类黄酮途径中晚期生物合成基因的表达，从而产生花青素或原花青素。近年来的研究进展表明，控制拟南芥中表皮细胞命运决定和花色苷生物合成的转录调控网络要比以前想象的要复杂得多。特别是，已经确定了更多的GL2调节剂，并且已经证明GL2参与了花色苷生物合成的调节。综述了拟南芥中GL2表达调控的研究进展，以及GL2在表皮细胞命运测定和花色苷生物合成调控中的作用。