阿拉伯芥HSA32調控長期後天耐熱性與HSP101降解途徑之研究

熱鍛鍊增強植物對劇烈熱逆境的耐受力，這個現象又稱為後天耐熱性。先前研究發現缺乏HSA32的阿拉伯芥及水稻幼苗有長期後天耐熱性缺陷，但是保有短期後天耐熱性。結果顯示HSA32係藉由抑制HSP101的降解，以延遲後天耐熱性之衰退，可是HSP101降解與HSA32調節HSP101穩定性的機制仍然不清楚。已知蛋白質降解主要經由26S蛋白酶體與細胞自噬作用兩種途徑，欲了解HSP101經何種機制分解，本實驗利用強效之26S蛋白酶體抑制劑bortezomib與細胞自噬突變株atg5分別阻礙這兩種途徑。結果顯示阻礙任一途徑皆只能部分抑制HSP101降解，然而將hsa32 atg5雙突變株施以bortezomib同時阻礙兩條蛋白質降解途徑時，HSP101的降解速率回復至野生型水平。根據實驗結果總結，受熱誘導產生的HSP101在植物回到室溫後，會經由26S蛋白酶體與細胞自噬逐漸分解，而HSA32的作用在於抑制HSP101透過這兩個途徑降解。

關鍵字

阿拉伯芥； HSA32 ； HSP101 ；長期後天耐熱性；細胞自噬； 26S 蛋白酶體

並列摘要

Heat acclimation enhances plant thermotolerance against severe heat stress, a phenomenon known as acquired thermotolerance. Previous research demonstrated that Arabidopsis and rice seedlings of HSA32 knockout (hsa32) mutant have defect in long-term acquired thermotolerance (LAT), but retain normal short-term acquired thermotolerance (SAT). It was shown that HSA32 regulates LAT by specifically preventing HSP101 from degradation. However, the mechanisms of HSP101 degradation and HSA32-mediated HSP101 stability remain unclear. Proteolysis can be categorized into 26S proteasome and autophagy pathways. The strong 26S proteasome inhibitor bortezomib and autophagy related mutant atg5 were used to specifically block proteolysis pathways to investigate which route is responsible for the degradation of HSP101. The results demonstrated that blocking either pathway in the absence of HSA32 resulted in partial suppression of HSP101 degradation. However, when hsa32 atg5 double mutant was treated with bortezomib, the HSP101 level was restored to that of the wild type. Taken together, the results show that HSP101 undergoes post-stress degradation through both 26S proteasome and macroautophagy pathways, which is suppressed by HSA32.

並列關鍵字

Arabidopsis thaliana ； HSA32 ； HSP101 ； Long-term acquired thermotolerance ； Autophagy ； 26S proteasome

參考文獻

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阿拉伯芥HSA32調控長期後天耐熱性與HSP101降解途徑之研究

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