Molecular mechanisms underlying thermal sensitivity of male reproduction

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Like humans, most flowering plants reproduce sexually. Sexual reproduction in flowering plants is important, as it produces the seeds that comprise 60% of our food. Sexual reproduction, especially on the male side, is the stage of plant life most vulnerable to temperature damage. For example, heat stress causes a dramatic decrease in the yield of major crops such as wheat and rice, primarily due to impaired male (pollen) development. As temperature extremes caused by climate change become more frequent, understanding temperature's impact on plant fertility is crucial for feeding the world.Recently, we discovered that defects in a male tissue called tapetum are the likely cause of thermal sensitivity during male development. Tapetum provides nutrition to the developing pollen, and under high temperature the tapetum becomes abnormally vacuolated and the pollen grains are unable to mature. We also developed state-of-the-art methods for tapetal cell isolation and gene expression studies, and found that a gene regulatory mechanism called DNA methylation is important for tapetal thermotolerance. Employing a genetic screen, we identified two mutant plants with enhanced fertility at high temperature.Our findings and technical advances put us in a unique position to understand the molecular mechanisms underlying male thermosensitivity. Our specific objectives are to: 1) reveal the molecular basis of tapetal sensitivity to heat, 2) understand how the DNA methylation pathway mediates heat tolerance in the tapetum, and 3) uncover novel genes involved in reproductive thermotolerance. We believe knowledge generated from this work will lay a solid foundation for understanding heat sensitivity during male reproduction, and can be exploited to improve the resilience of crops to heat stress, or engineer conditional male sterility lines valuable for hybrid breeding.