Department of Cellular Molecular Biology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, 50-383, Poland.
Plant Physiol. 2021 Oct 5;187(2):769-786. doi: 10.1093/plphys/kiab296.
The threat of global warming makes uncovering mechanisms of plant tolerance to long-term moderate heat stress particularly important. We previously reported that Arabidopsis (Arabidopsis thaliana) plants lacking mitochondrial proteases FTSH4 or OMA1 suffer phenotypic changes under long-term stress of 30°C, while their growth at 22°C is not affected. Here we found that these morphological and developmental changes are associated with increased accumulation of insoluble mitochondrial protein aggregates that consist mainly of small heat-shock proteins (sHSPs). Greater accumulation of sHSPs in ftsh4 than oma1 corresponds with more severe phenotypic abnormalities. We showed that the proteolytic activity of FTSH4, and to a lesser extent of OMA1, as well as the chaperone function of FTSH4, is crucial for protecting mitochondrial proteins against aggregation. We demonstrated that HSP23.6 and NADH dehydrogenase subunit 9 present in aggregates are proteolytic substrates of FTSH4, and this form of HSP23.6 is also a substrate of OMA1 protease. In addition, we found that the activity of FTSH4 plays an important role during recovery from elevated to optimal temperatures. Isobaric tags for relative and absolute quantification (iTRAQ)-based proteomic analyses, along with identification of aggregation-prone proteins, implicated mitochondrial pathways affected by protein aggregation (e.g. assembly of complex I) and revealed that the mitochondrial proteomes of ftsh4 and oma1 plants are similarly adapted to long-term moderate heat stress. Overall, our data indicate that both FTSH4 and OMA1 increase the tolerance of plants to long-term moderate heat stress by reducing detergent-tolerant mitochondrial protein aggregation.
全球变暖的威胁使得揭示植物耐受长期中度热应激的机制变得尤为重要。我们之前曾报道过，拟南芥（Arabidopsis thaliana）中缺失线粒体蛋白酶 FTSH4 或 OMA1 的植株在 30°C 的长期胁迫下会出现表型变化，而在 22°C 下的生长不受影响。在这里，我们发现这些形态和发育变化与不可溶的线粒体蛋白聚集体的积累增加有关，这些聚集体主要由小热休克蛋白（sHSPs）组成。ftsh4 中 sHSPs 的积累比 oma1 更多，对应着更严重的表型异常。我们表明，FTSH4 的蛋白水解活性（在一定程度上还有 OMA1 的活性）以及 FTSH4 的伴侣功能对于保护线粒体蛋白免受聚集至关重要。我们证明了 HSP23.6 和 NADH 脱氢酶亚基 9 在聚集体中是 FTSH4 的蛋白水解底物，这种形式的 HSP23.6 也是 OMA1 蛋白酶的底物。此外，我们发现 FTSH4 的活性在从高温恢复到最佳温度的过程中起着重要作用。基于等压标签相对和绝对定量（iTRAQ）的蛋白质组学分析，以及对易聚集蛋白的鉴定，表明受蛋白聚集影响的线粒体途径（例如复合物 I 的组装）受到影响，并揭示了 ftsh4 和 oma1 植物的线粒体蛋白质组对长期中度热应激具有相似的适应性。总的来说，我们的数据表明，FTSH4 和 OMA1 都通过减少去污剂耐受的线粒体蛋白聚集体来提高植物对长期中度热应激的耐受性。
