The proposed research address a critical world-wide food security challenge by generating fundamental scientific insights of importance to developing crop plants with improved heat-stress tolerance during pollination. By the year 2050, projections indicate that world-wide food production must increase by 70% in order to feed an expected world population of 9 billion people. Temperature stress is a major contributor to crop loss around the world, with pollen infertility being one of the most important underlying causes. Fertilization during plant reproduction is highly sensitive to hot and cold temperatures, with even a single hot day or cold night carrying the potential to disrupt reproductive success. Understanding this vulnerability is significant because most of the world's food supply is derived from seed crops that depend on pollination. The transformative potential of the proposed research is derived from pioneering the use of pollen as a model system to gain molecular and genetic insights into thermo-tolerance mechanisms in plants. Additional contributions to broader impacts will occur through co-mentoring graduate students in a collaboration involving two institutions, the University of Nevada (Reno) and Bar-Ilan University, Israel. Both institutions share a common goal of increasing agricultural productivity in arid land environments.
The long-term goal is to understand how different plant cells cope with abiotic stress, and to use that knowledge to improve crop productivity. The focus here is on how pollen sense and respond to heat stress during a limited period of time in which they must grow, locate ovules, and discharge male gametophytes to fertilize egg cells. The central hypothesis guiding the proposed research is that a protective heat-stress response in pollen involves signaling pathways that utilize calcium and ROS (reactive oxygen species) to trigger unique pollen-specific changes in the transcriptome. Specific Aim 1 employs a pollen transmission assay to genetically test more than 80 candidate genes for their potential to increase or decrease pollen fertility during a heat stress. Aim 2 is to identify heat-stress dependent changes in the transcriptome that are correlated to managing or responding to changes in cellular levels of ROS. This aim will involve using a fluorescence-activated cell sorter to isolate sub-populations of heat-stressed pollen that show either high or low levels of ROS, and thereby enable a transcriptome comparison to be made between two subpopulations of cells showing differences in their response to heat. Aim 3 is to use a quantitative proteomics strategy to identify heat-stress dependent changes in post-translational modifications, such as changes in phosphorylation of transcription factors. A unifying goal is to identify candidate genes or post-translational modifications that can be manipulated to improve heat-stress tolerance in pollen.
