Mechanisms of Rapid Alkalinization Factor Induced Growth Arrest in Arabidopsis

描述(申请人提供)：是什么决定了多细胞生物体的形状和大小，这是生物学中的一个基本问题。植物提供了一个相对简单的系统来研究这个问题，因为它们的组织和细胞类型比动物少。本研究的目的是了解多肽激素快速碱化因子(RALF)拮抗植物生长，特别是细胞伸长的分子机制。外源Ralf肽在幼苗生长中的应用导致根和地上部的生长停滞，Ralf的系统过度表达导致半矮化植株。所有被检查的植物基因组都至少包含一个Ralf多肽编码基因，这表明它在植物生长中起着重要作用。Ralf诱导生长停滞的分子细节目前尚不清楚，了解这种多肽激素如何影响生长可以使植物生物学家操纵植物结构来改良作物。这项提案中概述的实验结合了生理学、基因组和遗传学方法来了解模式植物拟南芥中Ralf的功能。具体地说，这些实验旨在了解Ralf信号如何拮抗生长素和油菜素类固醇诱导的幼苗生长，并通过对RALF1多肽处理的幼苗进行基因芯片实验来发展转录生长网络。基因筛查的设计是为了发现拉尔夫诱导的生长停滞所需的基因。到目前为止，植物多肽激素的受体已经被描述为富含亮氨酸的重复受体样激酶(LRR-RLK)，我们预计Ralf多肽受体也将是LRR-RLK。在动物系统中，LRR-RLK在器官发育和免疫中起着重要作用；因此，了解这些类型的受体如何发挥作用将具有广泛的意义。总之，这些实验将开始解开Ralf作用的机制，并显著增加目前植物细胞如何生长的模型。

DESCRIPTION (provided by applicant): What determines the shape and size of multicellular organisms is a fundamental question in biology. Plants offer a relatively simple system to study this question because they have fewer tissues and cell types than animals. The objective of this study is to understand the molecular mechanisms by which the peptide hormone Rapid Alkalinization Factor (RALF) antagonizes plant growth, specifically cell elongation. Application of exogenous RALF peptide to growing seedlings causes growth arrest of both roots and shoots, and systemic over-expression of RALF results in semi-dwarf plants. All plant genomes examined contain at least one RALF peptide-encoding gene, pointing to a fundamental role in plant growth. The molecular details of RALF-induced growth arrest are currently unknown, and understanding how this peptide hormone influences growth could allow plant biologists to manipulate plant architecture for the improvement of crops. The experiments outlined in this proposal combine physiological, genomic, and genetic approaches to understand RALF function in the model plant Arabidopsis thaliana. Specifically, the experiments are designed to understand how RALF signaling antagonizes auxin and brassinosteroid-induced growth in seedlings and to develop a transcriptional growth network by performing microarray experiments with seedlings treated with RALF1 peptide. Genetic screens have been designed to discover genes required for RALF-induced growth arrest. Receptors for plant peptide hormones described to date have been leucine rich repeat receptor-like kinases (LRR-RLKs), and we anticipate that a RALF peptide receptor would also be an LRR-RLK. LRR-RLKs in animal systems play important roles in organ development and immunity; therefore, understanding how these types of receptors function will have wide reaching implications. Together, these experiments will begin to unravel the mechanisms RALF action and add significantly to the current model of how plant cells grow.