Molecular mechanisms underlying thermal sensitivity of male reproduction

像人类一样，大多数开花植物都是有性繁殖。开花植物的有性繁殖很重要，因为它产生的种子占我们食物的60%。有性生殖，特别是雄性的有性生殖，是植物生命中最容易受到温度伤害的阶段。例如，热胁迫导致主要作物如小麦和水稻的产量急剧下降，主要是由于雄性（花粉）发育受损。随着气候变化导致的极端温度变得越来越频繁，了解温度对植物生育力的影响对于养活世界至关重要。最近，我们发现雄性绒毡层组织的缺陷可能是雄性发育过程中热敏感性的原因。绒毡层为发育中的花粉提供营养，在高温下绒毡层异常液泡化，花粉粒不能成熟。我们还开发了用于绒毡层细胞分离和基因表达研究的最先进方法，并发现称为DNA甲基化的基因调控机制对绒毡层耐热性很重要。通过遗传筛选，我们发现了两种在高温下育性增强的突变体植物。我们的发现和技术进步使我们处于一个独特的位置，以了解雄性热敏性的分子机制。我们的具体目标是：1）揭示绒毡层对热敏感的分子基础，2）了解DNA甲基化途径如何介导绒毡层的耐热性，3）发现新的基因参与生殖耐热性。我们相信，从这项工作中产生的知识将为理解雄性生殖过程中的热敏感性奠定坚实的基础，并可用于提高作物对热胁迫的适应性，或设计对杂交育种有价值的条件雄性不育系。

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.