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，调节植物生长发育的各个方面，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，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，但其作用的主要分子机制尚不清楚。过去10年积累的实验证据表明，该激素在转录水平上迅速（3-5分钟）调节多种基因（如Aux/IAAs、SAURs和GHs）的表达。生长素诱导的早期Aux/IAA基因表达部分是由Aux/IAA蛋白与ARFs（生长素反应因子）相互作用介导的。这种相互作用是由生长素介导的Aux/IAA蛋白水解降解调节的。Aux/IAA蛋白是与arf相互作用的转录因子，它们共同控制着生长素调控的一系列发育过程中涉及的大量基因。该提案的具体目标是：1。对大多数Aux/IAA和ARF基因家族成员的零突变进行表征，并构建高阶突变以阐明这些蛋白的生物学功能。这些零突变将用于RNA谱分析，以确定受Aux/IAA和ARF基因家族成员调控的下游基因，并用于生化研究。为了确定部分ARF基因家族成员的DNA结合特异性，利用酵母分子遗传筛选确定了ARF1和ARF6的DNA结合域，并利用微阵列技术确定了它们的基因组结合位点。为了分子表征最近克隆的age1突变，早期Aux/IAA基因表达的负调节因子。AGE1是酵母RAD3和人XPD/ERCC2蛋白的同源物，是TFIIH转录因子的一个组分，参与核苷酸切除修复（NER）和基础转录。克隆和表征生长素信号通路的另一个负调节因子age2突变。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.