CAREER: Molecular Characterization of the Vernalization-Responsive Block to Flowering in Winter-Annual Arabidopsis

为了最大限度地提高繁殖成功率，植物已经进化出了调节开花时间的机制，以响应内源和环境因素。在温带气候中，冬季漫长的低温为二年生植物和冬生植物提供了季节性的标志。这些物种（包括许多农作物）含有开花障碍，因此在冬季之前开花被阻止，而在春季开花。通过长时间的低温处理（如冬季）促进开花被称为春化。在了解模式植物拟南芥春化过程方面取得了重大进展。在拟南芥中，春化是由两个基因的相互作用引起的，开花位点C （FLC）的作用是阻止开花，而FRIGIDA （FRI）是FLC高水平表达所必需的。寒冷导致FLC基因表达的表观遗传抑制，可能在染色质修饰水平上通过组蛋白乙酰化。为了剖析FLC和FRI之间的调控相互作用，进行了详尽的突变体筛选。这种筛选导致FRI上调FLC所需的基因（称为FS基因）的分离。本文的目的是利用遗传学、分子遗传学和生化方法来表征FS基因在开花时间调控中的作用。这些研究将主要包括：1)双突变体分析，以表征各种FS基因之间的遗传关系；2)酵母双氢筛选，鉴定各种FS蛋白之间的相互作用；3)微阵列分析分离FS基因产物下游靶点。FS在其他早期流动的拟南芥植株中的作用也将被研究。更广泛的影响：由于通过染色质修饰的基因表达变化已经在广泛的真核生物中被记录下来，包括酵母、果蝇、秀丽隐杆线虫和人类，因此这项研究很可能会提供具有广泛科学兴趣的新知识。这项工作也有潜在的农业应用，因为大多数作物物种是二年生植物，操纵它们的开花时间的能力可能为作物改良提供途径。在人力资源方面，该研究将为本科生、研究生和博士后提供肥沃的培养土壤。植物发展教育模块也将为本科遗传学学生和广大公众开发。

To maximize reproductive success, plants have evolved mechanisms to regulate flowering time in response to both endogenous and environmental cues. In temperate climates, the prolonged cold temperature of winter provides a seasonal landmark for biennial and winter-annual plants. These species (which include many crop plants) contain a block to flowering such that flowering is prevented prior to winter and promoted in the spring. The promotion of flowering by prolonged cold treatment (as winter) is known as vernalization. Significant headway has been made in understanding the process of vernalization in the model plant Arabidopsis thaliana. In Arabidopsis, vernalization is caused by the interaction of two genes, FLOWERING LOCUS C (FLC), which acts to block flowering, and FRIGIDA (FRI), which is required for high levels of FLC expression. Cold causes an epigenetic repression of FLC gene expression, likely at the level of chromatin modification via histone acetylation. To dissect the regulatory interactions between FLC and FRI, an exhaustive mutant screen has been conducted. This screen led to the isolation of genes that are required for the upregulation of FLC by FRI (termed FS genes). The purpose of this proposal is to characterize the role of the FS genes in flowering-time regulation, using genetic, molecular genetic, and biochemical approaches. These studies will primarily involve: 1) double mutant analyses to characterize the genetic relationships among the various FS genes; 2) yeast two-hydrid screens to identify interactors among the various FS proteins; and 3) microarray analyses to isolate downstream targets of the FS gene products. The role of FS in other early-flowing accessions of Arabidopsis will also be examined.Broader Impacts: Because changes in gene expression through chromatin modification have been documented in a broad range of eukaryotes, including yeast, Drosophila, C. elegans, and humans, there is a high likelihood that this research will provide new knowledge that will be of broad scientific interest. This work also has potential agricultural applications, inasmuch as most crop species are biennials and the ability to manipulate their flowering time might provide avenues for crop improvement. In terms of human resources, the research will provide a fertile training ground for undergraduates, graduate students and postdoctoral fellows. Plant-development education modules will be also developed for both undergraduate genetics students and the public at large.