UNCOVERING DEVELOPMENTAL MECHANISMS TO SUSTAIN GRAIN NUMBER DURING HEAT STRESS

In light of the pattern of increased frequency of extreme temperature events in recent years, this project aims to accelerate breeding efforts in cereals through a functional genomic understanding of the responses to heat stress during early seed development.To achieve this goal, we will elucidate genetic networks that regulate heat responses in spike development in durum wheat through the following objectives:Determine chromatin structure dynamics during rachis elongation due to heat stressChromatin structure is sensitive to stresses and contributes to the regulation of gene expression which ultimately orchestrates development dependent on the environment. For this objective, we will attempt to use the approach of ATAQ-seq, which enables measurement of chromatin accessibility genome-wide. In this process, we will use a transgenic durum wheat line in which the nuclei are tagged with biotin, enabling magnetic isolation of the nuclei. This process will be performed at multiple timepoints with and without heat stress to determine how chromatin structure is affected.2. Determine gene expression dynamics during rachis elongation due to heat stressThe formation of the head of cereals is altered during heat stress, influencing elongation and positioning of spikelets. To study this development, we will measure mRNA expression during head development with and without heat stress.3. Infer gene regulatory network dynamics due to heat stressFor this objective, we will infer transcription factor binding based on chromatin accessibility and mRNA expression of transcription factors. Using the data produced in Objectives 1 and 2 along with publicly available describing the conserved binding preferences of major families of transcription factors, we will infer the regulatory networks underlying response to heat stress in the developing head.4.Track differences in floret fertility and sensitivity due to heat stressThroughout normal head development, floret degenerate, reducing the total number of grains produced. The mechanisms underlying this process is unknown and how it relates to the reduced number of grains due to heat stress is unclear. Therefore, we will track the patterns of floret fertility due to pollen and ovary and how this varies with heat stress.5. Identify expression differences underlying floret fertility upon heat stress.In order to begin to isolate the mechanisms underlying floret degeneration and infertility from Objective 4, we will measure expression differences across distal and proximal florets exposed to heat stress.