Heat stress poses a significant threat to grain yield. As an α2 subunit of the 26S proteasome, TT1 has been shown to act as a critical regulator of rice heat tolerance. However, the heat tolerance mechanisms mediated by TT1 remain elusive. In this study, we unveiled that small ubiquitin-like modifier (SUMO)-conjugating enzyme 1 (SCE1), which interacts with TT1 and acts as a downstream component of TT1, is engaged in TT1-mediated 26S proteasome degradation. We showed that SCE1 functions as a negative regulator of heat tolerance in rice, which is associated with its ubiquitination modification. Furthermore, we observed that small heat-shock proteins (sHSPs) such as Hsp24.1 and Hsp40 can undergo SUMOylation mediated by SCE1, leading to increased accumulation of sHSPs in the absence of SCE1. Reducing protein levels of SCE1 significantly enhanced grain yield under high-temperature stress by improving seed-setting rate and rice grain filling capacity. Taken together, these results uncover the critical role of SCE1 in the TT1-mediated heat tolerance pathway by regulating the abundance of sHSPs and SUMOylation, and ultimately modulating rice heat tolerance. These findings underscore the great potential of the TT1–SCE1 module in improving the heat tolerance of crops.

中文翻译：

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TT1-SCE1 模块整合泛素化和 SUMO化以调节水稻的耐热性


热应激对粮食产量构成重大威胁。作为 26S 蛋白酶体的 α2 亚基，TT1 已被证明是水稻耐热性的关键调节因子。然而，TT1 介导的耐热机制仍然难以捉摸。在这项研究中，我们揭示了小泛素样修饰物 （SUMO） 结合酶 1 （SCE1） 与 TT1 相互作用并作为 TT1 的下游组分，参与 TT1 介导的 26S 蛋白酶体降解。我们发现 SCE1 在水稻中起耐热性的负调节因子的作用，这与其泛素化修饰有关。此外，我们观察到 Hsp24.1 和 Hsp40 等小热休克蛋白 （sHSP） 可以经历 SCE1 介导的 SUMO化，导致在没有 SCE1 的情况下 sHSP 的积累增加。降低 SCE1 蛋白水平通过提高结实率和水稻籽粒灌浆能力，显著提高高温胁迫下的籽粒产量。综上所述，这些结果揭示了 SCE1 通过调节 sHSP 和 SUMOylation 的丰度，并最终调节水稻耐热性，在 TT1 介导的耐热途径中发挥关键作用。这些发现强调了 TT1-SCE1 模块在提高作物耐热性方面的巨大潜力。