RESEARCH-PGR: Genomic analysis of heat stress tolerance during tomato pollination

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High temperatures during flowering and pollination can result in significant fruit losses, because of heat sensitivity of pollen tube growth. Different tomato varieties show significant differences in heat sensitivity of pollen tube growth. Making use of this naturally occurring variety, this project seeks to identify the molecular basis of adaptations that mitigate the yield-damaging consequences of heat stress during crop reproduction. The goal is to develop new tomato varieties that are fertile and continue to produce fruits at high temperature. This project will train undergraduate and graduate students and postdoctoral fellows in genome science, developmental biology, and computational analysis of genetic variation. The project will build on the successful outreach program developed by one of the team members. This program has been used to teach plant genetics and the science of plant breeding and genetic engineering to more than 1000 9th grade students, tailoring it to focus on the effects of temperature stress on tomato reproduction.It is hypothesized that thermotolerant tomato varieties express a pollen tube heat stress response that is either absent or diminished in thermosensitive cultivars and that the thermotolerant pistil buffers heat stress and facilitates pollen tube growth. To identify the molecular mechanisms of thermotolerance in tomato, transcription changes that accompany heat stress in pollen tubes and pistil will be measured in heat tolerant and heat sensitive tomato varieties. Haploid selection mapping of pollen tube heat tolerance will be performed, followed by experimental tests whether identified candidate genes are causally related to heat tolerance. This project will generate accessible and readily available community databases 1) detailing reproductive gene expression responses to elevated temperature and 2) registering genetic variants across hundreds of tomato genomes to enable analysis of heat stress adaptation and other traits. The project will define the transcriptional changes that accompany heat stress in the pollen tube and pistil (Aim 1), genetic variation responsible for pollen tube thermotolerance (Aims 2 and 3), and the functions of individual thermotolerance genes using reverse genetics (Aim 4).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.