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

Indiana University, Bloomington IN

Investigators

Abstract

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.