Biotechnology Department, Agricultural University of Athens, 11855 Athens, Greece.
Laboratory of Virology, Scientific Directorate of Phytopathology, Benaki Phytopathological Institute, 14561 Athens, Greece.
Int J Mol Sci. 2022 Dec 21;24(1):88. doi: 10.3390/ijms24010088.
Circuitries of signaling pathways integrate distinct hormonal and environmental signals, and influence development in plants. While a crosstalk between brassinosteroid (BR) and gibberellin (GA) signaling pathways has recently been established, little is known about other components engaged in the integration of the two pathways. Here, we provide supporting evidence for the role of HSP90 (HEAT SHOCK PROTEIN 90) in regulating the interplay of the GA and BR signaling pathways to control hypocotyl elongation of etiolated seedlings in Arabidopsis. Both pharmacological and genetic depletion of HSP90 alter the expression of GA biosynthesis and catabolism genes. Major components of the GA pathway, like RGA (REPRESSOR of ) and GAI (GA-INSENSITIVE) DELLA proteins, have been identified as physically interacting with HSP90. Interestingly, GA-promoted DELLA degradation depends on the ATPase activity of HSP90, and inhibition of HSP90 function stabilizes the DELLA/BZR1 (BRASSINAZOLE-RESISTANT 1) complex, modifying the expression of downstream transcriptional targets. Our results collectively reveal that HSP90, through physical interactions with DELLA proteins and BZR1, modulates DELLA abundance and regulates the expression of BZR1-dependent transcriptional targets to promote plant growth.
信号通路的电路整合了不同的激素和环境信号，并影响植物的发育。虽然油菜素内酯（BR）和赤霉素（GA）信号通路之间的串扰最近已经建立，但对于参与这两个通路整合的其他成分知之甚少。在这里，我们提供了 HSP90（热休克蛋白 90）在调节 GA 和 BR 信号通路相互作用以控制拟南芥黄化幼苗下胚轴伸长中的作用的证据。HSP90 的药理学和遗传耗竭都改变了 GA 生物合成和分解代谢基因的表达。GA 途径的主要成分，如 RGA（抑制物）和 GAI（GA-不敏感）DELLA 蛋白，已被确定为与 HSP90 物理相互作用。有趣的是，GA 促进的 DELLA 降解依赖于 HSP90 的 ATPase 活性，而 HSP90 功能的抑制稳定了 DELLA/BZR1（BRASSINAZOLE-RESISTANT 1）复合物，改变了下游转录靶标物的表达。我们的研究结果表明，HSP90 通过与 DELLA 蛋白和 BZR1 的物理相互作用，调节 DELLA 的丰度并调节 BZR1 依赖性转录靶标的表达，从而促进植物生长。
