Crop fertility loss due to extreme temperatures threatens the world's food supply. Many factors contribute to heat sensitivity of flowering plant reproduction, including reduced production and viability of gametophytes due to chronic heat stress. However, even when vegetative and gametophyte development occur at optimal temperatures, acute heat stress during the few hours it takes pollen tubes to grow to ovules has the potential to completely block seed production. Very little is known about how this critical phase of plant reproduction responds to temperature stress. We focus on the pollen tube, pistil, and the interactions between them to define networks of transcriptional and physiological responses that underlie thermotolerant reproduction in tomato. This is an excellent model system with wild and cultivated genetic diversity, adaptation to a wide array of climates, and excellent genomic resources. Pollen tube growth is thermosensitive in most tomato varieties and fails when temperatures exceed narrow tolerances. We identified tomato cultivars bred for high temperature fruit set and found four that produce pollen tubes that extend at supraoptimal temperatures. These data suggest that gene variants conferring high temperature pollen tube growth have been selected in these cultivars. Moreover, we found that the pistil of some thermotolerant genotypes is able to modulate the heat stress response of the thermosensitive pollen tube. Interestingly, we found that thermotolerant varieties have a different transcriptional and physiological response to temperature stress than thermosensitive varieties and that some temperature stress response pathways in vegetative tissue may not operate in growing pollen tubes. We will report on our progress toward defining how the pollen tube and pistil respond to temperature stress and identifying gene variants that confer thermotolerant plant reproduction.
Coauthors: Sorel Ouonkap Yimga – Brown University;Robert Reid – University of North Carolina Charlotte;Bejamin Styler – Brown University;Nathaniel Ponvert – Brown University;James Pease – Wake Forest University;Joëlle Mühlemann – Wake Forest University;Gloria Muday – Wake Forest University;Ann Loraine – University of North Carolina Charlotte;Ravishankar Palanivelu – University of Arizona