The Aux/IAA and ARF Gene Families in Auxin Signaling

描述（由申请人提供）：植物激素生长素，以吲哚-3-乙酸（IAA）为代表，调节植物生长和发育的各个方面，例如细胞分裂、维管分化、侧根形成、顶端优势、形态发生、肿瘤发生、向性，并且通常被认为负责调节植物细胞生长。尽管生长素在植物发育中的重要性，但生长素作用的主要分子机制知之甚少。在过去10年中积累的实验证据表明，该激素在转录水平上快速（3-5分钟）作用，调节多种基因（如Aux/IAAs、SAUR和GH）的表达。生长素诱导的Aux/IAA基因的早期表达部分是由Aux/IAA蛋白与ARF（auxin responsive factors）的相互作用介导的。这种相互作用是由生长素介导的Aux/IAA蛋白的蛋白水解降解调节的。Aux/IAA蛋白是与ARF相互作用的转录因子，并且共同控制参与由生长素调节的大范围发育过程的大量基因。该提案的具体目标是：1。研究Aux/IAA和ARF基因家族成员的无效突变，构建更高级的突变体，以阐明这些蛋白的生物学功能。无效突变将用于RNA分析以确定由Aux/IAA和ARF基因家族成员中的一些调控的下游基因，以及用于生物化学研究。为了确定ARF基因家族成员的DNA结合特异性，利用酵母分子遗传学筛选确定了ARF 1和ARF 6的DNA结合结构域，并利用基因芯片技术确定了其基因组结合位点.对新近克隆的Aux/IAA基因早期表达负调控因子age 1突变进行分子特征分析。AGE 1是酵母RAD 3和人XPD/ERCC 2蛋白的同源物，其是参与核苷酸切除修复（NER）和基础转录的TFIIH转录因子的组分。克隆和鉴定生长素信号通路的另一个负调控因子age 2突变体，阐明生长素作用的主要机制在植物科学中具有重要意义。

DESCRIPTION (provided by applicant): The plant hormone auxin, typified by indole-3-acetic acid (IAA), regulates various aspects of plant growth and development such as cell division, vascular differentiation, lateral root formation, apical dominance, morphogenesis, oncogenesis, tropisms, and is generally considered to be responsible for regulating plant cell growth. Despite the importance of auxin in plant development, the primary molecular mechanism of auxin action is poorly understood. Experimental evidence accumulated during the past 10 years indicates that the hormone acts rapidly (3-5 min) at the transcriptional level regulating expression of a variety of genes such as Aux/IAAs, SAURs, and GHs. Early auxin-induced Aux/IAA gene expression is mediated in part by the interaction of Aux/IAA proteins with the ARFs (auxin responsive factors). This interaction is regulated by auxin-mediated proteolytic degradation of Aux/IAA proteins. The Aux/IAA proteins are transcription factors that interact with the ARFs and together control a large number of genes involved in a large spectrum of developmental processes regulated by auxin. The specific aims of the proposal are:1. To characterize null mutations for most of the Aux/IAA and ARF gene family members and construct higher order mutations for elucidating the biological function of these proteins. The null mutations will be used for RNA profiling to determine the downstream genes that are regulated by some of the Aux/IAA and ARF gene family members, and for biochemical studies.2. To determine the DNA binding specificities of some ARF gene family members, define the DNA binding domains of ARF1 and ARF6 using a yeast molecular genetic screen, and determine their genomic binding sites with microarray technology.3. To molecularly characterize the recently cloned age1 mutation, a negative regulator of early Aux/IAA gene expression. AGE1 is a homolog of the yeast RAD3 and human XPD/ERCC2 protein, which is a component of the TFIIH transcription factor that participates in nucleotide excision repair (NER) and basal transcription. To clone and characterize the age2 mutation, another negative regulator of the auxin signaling pathway.The elucidation of the primary mechanisrn of auxin action is of paramount importance in Plant Science.