Cryptochromes (crys) are photolyase-like blue-light receptors first discovered in Arabidopsis thaliana and later identified in all major evolutionary lineages. Crys are involved in not only blue light responses but also in temperature responses; however, whether and how cry protein stability is regulated by temperature remains unknown. Here, we show that cry2 protein abundance is modulated by ambient temperature and cry2 protein is degraded under low ambient temperature via the 26S proteasome. Consistent with this, cry2 shows high levels of ubiquitination under low ambient temperatures. Interestingly, cry2 degradation at low ambient temperatures occurs only under blue light and not under red light or dark conditions, indicating blue-light-dependent degradation of cry2 at low ambient temperature. Furthermore, low ambient temperature promotes physical interaction of Light-Response Bric-a-Brack/Tramtrack/Broad (LRB) proteins with cry2 to modulate its ubiquitination and protein stability in response to ambient temperature. LRBs promote high-temperature-induced hypocotyl elongation by modulating the protein stability of cry2 protein. These results indicate that cry2 accumulation is regulated by not only blue light but also ambient temperature, and LRBs are responsible for cry2 degradation at low ambient temperature. The stabilization of cry2 by high temperature makes cry2 a better negative regulator of temperature responses.

中文翻译：

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光响应 Bric-A-Brack/Tramtrack/Broad 蛋白介导隐花色素 2 响应低环境温度降解

隐花色素（crys）是一种类似光解酶的蓝光受体，首先在拟南芥中发现，后来在所有主要进化谱系中都得到了鉴定。哭泣不仅与蓝光反应有关，还与温度反应有关。然而，cry 蛋白稳定性是否以及如何受温度调节仍不清楚。在这里，我们表明cry2蛋白丰度受环境温度调节，并且cry2蛋白在低环境温度下通过26S蛋白酶体降解。与此一致的是，cry2 在低环境温度下表现出高水平的泛素化。有趣的是，低环境温度下的cry2降解仅在蓝光下发生，而不是在红光或黑暗条件下发生，表明cry2在低环境温度下的蓝光依赖性降解。此外，低环境温度会促进光响应 Bric-a-Brack/Tramtrack/Broad (LRB) 蛋白与cry2 的物理相互作用，从而调节其泛素化和蛋白质稳定性以响应环境温度。LRB 通过调节cry2 蛋白的稳定性来促进高温诱导的下胚轴伸长。这些结果表明cry2的积累不仅受到蓝光的调节还受到环境温度的调节，并且LRBs负责cry2在低环境温度下的降解。高温对cry2的稳定性使得cry2成为更好的温度响应负调节因子。