Analysis of the Regulation of TTG1-dependent Pathways

植物表皮是植物与环境的接触层，因此对控制气体交换、养分吸收、与昆虫和病害生物的相互作用以及光的透射等过程至关重要。拟南芥原胚层细胞分化为几种表皮细胞类型。在主根上只有两种细胞，发细胞和非发细胞。在叶片上有三到四种细胞类型：保护细胞、毛状体（和毛状体附属细胞）和铺装细胞。本研究旨在研究表皮细胞命运决定事件的过程和分子，以及花青素次生代谢途径的控制。植物表皮对细胞命运的控制是了解植物发育过程和最终了解植物如何与环境相互作用的一个有价值的模型系统。贯穿本提案的主题是了解依赖于关键的含有wd -repeat的多效表皮调节剂Transparent Testa Glabra 1 （TTG1）的过程。TTG1控制着不同的表皮通路，如茎毛和根毛分化、花青素色素产生和种皮粘液细胞分化。三个碱基-螺旋-环-螺旋位点的三重突变体，Glabra3， Glabra3的增强子，和TT8，表型上显示ttg1突变体。这些蛋白与TTG1、彼此之间以及与一系列myb元件形成蛋白-蛋白相互作用。当过表达时，这些bHLH蛋白可以抑制ttg1突变。提出了分子、遗传和生化实验来了解ttg1相关复合物的功能。该提案的具体目标包括：探索GL3， EGL3和TT8在毛状体起始和激活花青素途径中的差异作用；确定GL2和DFR启动子是否是bHLH/myb转录因子的直接靶点，并验证启动子歧视在myb水平的假设；继续表征TTG1在控制转录复合物活性中的作用；并致力于识别ttg1相关转录复合物的所有成员。更广泛的影响这个项目将产生更广泛的影响的一种方式是，从这里提出的研究所得的信息将增加我们对植物表皮细胞命运决定和植物次生代谢控制的基本知识。这些知识的最终用途包括操纵作物的能力，使它们能够更好地应对不同的环境，并使它们对牲畜和人类更有营养。另一个影响是，原创性研究为本科生、研究生和博士后提供了学习技术和创造性思维的机会。第三个影响将是劳埃德实验室成员和来自当地小学和奥斯汀社区学院（ACC）的学生。在过去的六年里，所有的实验室成员都参加了巴顿山小学年度科学博览会的评审。这包括小学生的互动访谈。在过去的三年里，劳埃德实验室为ACC的生物技术项目教授了一个实验部分。这个部分包括ACC的学生来UT做一个动手的植物转化和实验室机器人实验。

SummaryThe plant epidermis is the plant's environmental contact layer and, as such, is critical for controlling such processes as gas exchange, nutrient uptake, interactions with insects and disease organisms, and the transmission of light. The Arabidopsis protodermal cell differentiates into just a few epidermal cell types. On the primary root there are just two cell types, hair and non-hair. On the leaf there are three or four cell types, guard cell, trichome (and trichome subsidiary cell), and pavement cell. This proposal aims to study the processes and molecules that lead to epidermal cell fate decision events and control of the anthocyanin secondary metabolic pathway. The control of cell fate in the plant epidermis is a valuable model system for understanding plant developmental processes and eventually understanding how a plant interacts with its environment. The theme running through this proposal is to understand the processes that are dependent on a key WD-repeat-containing pleiotropic epidermal regulator, Transparent Testa Glabra 1 (TTG1). TTG1 controls such disparate epidermal pathways as shoot trichome and root hair differentiation, anthocyanin pigment production, and seed coat mucilage cell differentiation.Plants triple mutant for three basic-Helix-Loop-Helix loci, Glabra3, Enhancer of Glabra3, and TT8, phenocopy the ttg1 mutant. These proteins form protein-protein interactions with TTG1, with each other and with a series of myb elements. When overexpressed, these bHLH proteins can suppress the ttg1 mutation. Molecular, genetic and biochemical experiments are proposed to understand the function of the TTG1-associated complex.Specific goals for this proposal include: exploration of the differential roles for GL3, EGL3 and TT8 in trichome initiation and in activating the anthocyanin pathway; determination of whether the GL2 and DFR promoters are the direct targets of bHLH/myb transcription factors and test the hypothesis that promoter discrimination is at the myb level; continue the characterization of TTG1's role in controlling the activity of transcription complexes; and work towards identifying all members of TTG1-associated transcription complexes.Broader impactOne way this project will have a broader impact is that the information resulting from the research proposed here will increase our basic knowledge of the control of plant epidermal cell-fate decisions and plant secondary metabolism. Eventual uses of this knowledge include the ability to manipulate crops to make them better able to cope with diverse environments and to make them more nutritious for livestock and humans. Another impact will be that the original research provides opportunities for undergraduate, graduate and postdoctoral students to learn both technology and creative thinking. A third impact will be the felt by both Lloyd lab members and students from a local elementary and the Austin Community College (ACC). For the past six years, all lab members have participated in judging the yearly science fair at Barton Hills Elementary. This includes interactive interviews of the elementary students. For the past three years, the Lloyd lab has taught a lab section for the Biotechnology program at ACC. This section consists of the ACC students coming to UT to do a hands-on plant transformation and lab robotics experiments.