Analysis of GL3 and TTG1 Function in Trichome Development

理解细胞命运决定的过程是理解生物体个体发生的基础。 该项目的长期目标是了解细胞命运的决定是如何在发育中的植物表皮上做出和协调的。 在拟南芥叶片发育过程中，植物原皮层细胞必须经过有限的转换点才能形成成熟的组织系统。 其中一个开关决定了一个细胞是否会变成毛状体（毛）细胞。 在拟南芥中，遗传研究表明TTG 1，GL 1和GL 3在调节这种细胞命运决定中起重要作用。最近的初步工作已经确定，GL 3编码一个基本的HLH环HLH（bHLH）myc型蛋白质的同源性花青素调节，R，从玉米。 与R过表达非常相似，GL 3过表达导致野生型植物中产生额外的毛状体，并且它将抑制TTG 1（一种含有WD 40重复序列的蛋白质）中的突变。 然而，与R不同，GL 3是毛状体缺陷的弱抑制剂，这表明GL 3通常需要TTG 1来实现全部功能。 也像R一样，GL 3将与GL 1（一种myb型蛋白）相互作用，在过表达两者的转基因植物中。 酵母双杂交研究表明，GL 3通过其bHLH结构域外的氨基区域与GL 1相互作用，GL 3通过单独的氨基区域结构域与TTG 1相互作用。然而，GL 1不与TTG 1相互作用。 GL 3还可以通过bHLH区域与其他bHLH蛋白同源二聚化和异源二聚化。为了验证关于在双杂交分析中发现的蛋白质-蛋白质相互作用如何介导TTG 1对GL 3的调节的假设，进一步的工作将集中在定义野生型和突变体植物中TTG 1和GL 3的表达模式和亚细胞位置上。虽然ttg 1 -1和gl 1 -1突变几乎完全没有毛状体，但gl 3突变产生的毛状体比发育不太好的野生型少。 除GL 3外，拟南芥中至少还有一个高度同源的bHLH基因，当过表达时能够抑制ttg 1，并产生与GL 3相同的相互作用。 将采用遗传实验来试图确定GL 3是否是部分冗余基因座或gl 3突变不是无效的。了解细胞命运的决定是如何调节的是理解一般的发展和目前的研究将增加在这一领域迅速扩大的知识基础的基础。

Understanding the process of cell-fate determination is fundamental to understanding the ontogeny of an organism. The long term goal of this project is to understand how cell-fate decisions are made and coordinated on the developing plant epidermis. During the process of Arabidopsis leaf development, plant protodermal cells must pass through a limited number of switch points on the way to a mature tissue system. One of those switches determines whether a cell will become a trichome (hair) cell. In Arabidopsis thaliana, genetic studies indicate important roles for TTG1, GL1 and GL3 in regulating this cell-fate decision. Recent preliminary work has determined that GL3 encodes a basic-Helix-Loop-Helix (bHLH) myc-type protein with homology to the anthocyanin regulator, R, from maize. Much like R overexpression, GL3 overexpression leads to supernumerary trichome production in wild type plants and it will suppress mutations in TTG1, a WD40 repeat containing protein. However, unlike R, GL3 is a weak suppressor of the trichome defect indicating that GL3 normally requires TTG1 for full functionality. Also like R, GL3 will interact with GL1, a myb-type protein, in transgenic plants overexpressing both. Yeast 2-hybrid studies indicate that GL3 interacts with GL1 through its amino region outside of the bHLH domain and that GL3 interacts with TTG1 through a separate amino region domain. However, GL1 does not interact with TTG1. GL3 can also homodimerize and heterodimerize with other bHLH proteins through the bHLH region. In order to test hypotheses about how protein-protein interactions uncovered in the 2-hybrid analysis may mediate the regulation of GL3 by TTG1, further work will focus on defining the expression patterns and subcellular locations of TTG1 and GL3 in wild type and mutant plants. While the ttg1-1 and gl1-1 mutations are almost completely devoid of trichomes, the gl3 mutations make fewer trichomes than wild type that are less well developed. In addition to GL3, there is at least one other highly homologous bHLH gene in Arabidopsis that is able to suppress ttg1 when overexpressed and make the same interactions as GL3. Genetic experiments will be employed to try to determine whether GL3 is a partially redundant locus or that the gl3 mutations are not null. The understanding of how cell-fate decisions are regulated is fundamental to the understanding of development in general and the present studies will add to the rapidly expanding knowledge-base in this area.