Climate change has created an environment where heat stress conditions are becoming more frequent as temperatures continue to rise in crop production areas around the world. This situation leads to decreased crop production due to plant sensitivity to heat stress. Reproductive success is critically dependent on plants' ability to produce functional pollen grains, which are the most thermo-sensitive tissue. Flavonols are plant secondary metabolites known for their potent antioxidative activity, essential for male fertility in several species including tomato, and implicated in heat stress tolerance. Since flavonols are highly abundant in fruits of the tomato high pigment-2 (hp2) mutant, we tested the level of flavonols in pollen of this mutant, under the hypothesis that increased accumulation of flavonols would render pollen more tolerant to heat stress. Indeed, pollen from three alleles of the hp2 mutant were found to have flavonols levels increased by 40% on average compared with wild type under moderate chronic heat stress conditions. This mutant produced on average 7.8-fold higher levels of viable pollen and displayed better germination competence under heat stress conditions. The percentage of fully seeded fruits and the number of seeds per fruit were maintained in the mutant under heat stress conditions while decreased in wild-type plants. Our results strongly suggest that increased pollen flavonols content enhances pollen thermotolerance and reproductive success under heat stress conditions. Thus, the high flavonols trait may help frame the model for improving crop resilience to heat stress.

中文翻译：

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增强的生殖耐热性与番茄高色素2突变体花粉中黄酮醇的积累增加有关。

气候变化创造了一种环境，随着温度在世界各地的农作物生产地区持续升高，热应激条件变得越来越频繁。这种情况由于植物对热胁迫的敏感性而导致农作物减产。生殖的成功关键取决于植物产生功能性花粉粒的能力，而功能性花粉粒是对热最敏感的组织。黄酮醇是植物的次生代谢产物，以其强大的抗氧化活性而闻名，是包括番茄在内的多种物种的雄性育性所必需，并且与耐热性有关。由于番茄高色素2（hp2）突变体的果实中黄酮醇含量很高，因此我们测试了该突变体花粉中的黄酮醇含量，在黄酮醇积累增加的假设下，花粉对热胁迫的耐受性更高。实际上，发现在中等慢性热应激条件下，与野生型相比，来自hp2突变体的三个等位基因的花粉的黄酮醇水平平均提高了40％。在热应激条件下，该突变体产生的花粉水平平均提高了7.8倍，并表现出更好的发芽能力。在热胁迫条件下，该突变体中完全播种的果实百分比和每个果实的种子数保持不变，而在野生型植物中则降低。我们的结果强烈表明，花粉中黄酮含量的增加可提高花粉的耐热性和在热胁迫条件下的繁殖成功。从而，