Mechanisms of gene regulation by the plant MADS-domain transcription factor AGL15 and developmental outcomes.

University Of Kentucky Research Foundation, Lexington KY

Investigators

Abstract

AGL15 is a transcription factor involved in plant embryo development. Transcription factors are proteins that function by binding DNA and turning genes on or off. AGL15 is an example of a 'bimodal' factor that directly expresses some genes, but directly represses other genes, and the focus of this project is to understand how this occurs. Because mechanisms of dual functionality are not well understood in any organism, the proposed work will have broader relevance to understanding these types of factors. Furthermore, AGL15 is involved in seed development, and seeds are of critical importance to humans, with the majority of our diets directly derived from seeds. Additionally, work will contribute to understanding somatic embryogenesis, a step allowing genetic engineering of plants to meet agricultural challenges. Training will be provided for a postdoctoral scholar, a graduate student, and undergraduate researchers, including hosting interns from the nearby community college. This project will support a number of continuing outreach activities as well as developing a new relationship with an elementary school with a high percentage of students from economically disadvantaged homes. AGL15 is an Arabidopsis MADS-factor involved in developmental phase transitions that directly expresses some genes, but directly represses others. The mechanism of repression may be explained by AGL15's interaction with SAP18/TPL that is part of a histone deacetylase complex (HDAC). This interaction requires an LxLxL/EAR motif that is found within the C-terminal domain of AGL15. The yeast 2-hybrid screen that identified these interactions also isolated proteins that could account for how AGL15 recruitment to gene regulatory elements leads to expression of direct targets. These intriguing proteins, which include another MADS-factor, SEP3, that interacts with chromatin remodeling components and a plant-specific transcription factor (LBD40), will be further investigated, as will the HDAC interaction, and in planta interaction with AGL15 tested. The LxLxL motif, needed for recruitment of the HDAC complex, will be assessed for functional importance in development. Prior NSF support has allowed the PI's lab to map genome wide association of AGL15 with DNA sites and response of target genes. Similar determination of the in vivo association of AGL15 interacting proteins will allow co-occupancy to be determined that may be revealing for mechanism of regulatory outcomes. Some interactors will be assessed for how occupancy changes from embryo to seedling. Prior work on AGL15 has provided clues as to how different complexes with different regulatory outcomes are recruited to specific loci. While mapping association will aid in determining mechanism, experiments are also proposed to directly address the hypothesis that activation may involve multiple binding sites for AGL15 and looping, whereas repression does not. Finally, select targets will be further assessed for epigenetic regulation and function in development. Training at all levels of science are an integral part of the project.