Exposure of meiosis-to-microspore-stage tomato flowers to long-term mild heat results in pollen failure after mitosis.

Crop reproductive success is significantly challenged by heatwaves, which are increasing in frequency globally. The main reason is reduced male fertility due to abnormal pollen development, but the mechanism behind the developmental deviation is not well understood. Here, long-term mild heat (LTMH) treatment, mimicking a heatwave, was applied to flowers or whole plants and followed up by cytological, transcriptomic and biochemical analyses. LTMH was shown to act directly on the flowers and not via a systemic effect on other plant tissue. The meiosis to early microspore stage was the most to LTMH and three to four days of LTMH exposure around this period was sufficient to significantly reduce pollen viability. Extensive cytological analysis showed that abnormalities in pollen development could first be observed after pollen mitosis I and tapetum development appeared unaffected. Transcriptomic and biochemical analyses suggested that pollen development suffers from tapetal ER stress, with a limited role for oxidative stress. These characteristics differentiate the response of developing anthers and pollen to LTMH from that to severe heat stress. 12 samples in total, consisting of 3 sample types with 4 replicates each. Sample types: 1) control temperature (CT), 2) 1 day long-term mild heat (1D-LTMH), 3) 4 days long-term mild heat (4D-LTMH).

全球热浪发生频率持续升高，正显著威胁作物的生殖成功率。其中核心诱因是花粉发育异常导致雄性育性下降，但该发育偏差背后的调控机制仍未得到充分阐释。本研究采用模拟热浪的长期温和热胁迫（long-term mild heat, LTMH）处理植株花朵或整株植株，并通过细胞学、转录组学与生物化学分析开展跟踪研究。实验证实LTMH可直接作用于花朵，而非通过影响植株其他组织产生系统性效应。减数分裂至早期小孢子阶段是对LTMH最为敏感的发育时期，在此阶段前后施加3至4天的LTMH处理，即可显著降低花粉活力。全面的细胞学分析显示，花粉发育异常最早可在花粉有丝分裂I期后被观测到，且绒毡层（tapetum）发育未受显著影响。转录组学与生物化学分析结果表明，花粉发育过程中出现了绒毡层内质网应激（ER stress），而氧化应激所发挥的作用相对有限。上述特征使得发育中的花药与花粉对LTMH的响应模式，区别于其对极端热胁迫的响应。本数据集共包含12个样本，分为3种样本类型，每种类型设置4个生物学重复。样本类型分别为：1）对照温度组（control temperature, CT）；2）1天长期温和热胁迫组（1D-LTMH）；3）4天长期温和热胁迫组（4D-LTMH）。