Han Xiaofei, Wang Zi, Shi Lingyan, Wei Ziyang, Shangguan Jiaolei, Shi Liang, Zhao Mingwen
Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China.
School of Medicine, Henan Polytechnic University, Jiaozuo, Henan, China.
Appl Environ Microbiol. 2025 Feb 19;91(2):e0097924. doi: 10.1128/aem.00979-24. Epub 2025 Jan 29.
High temperature is an unavoidable environmental stress that generally exerts detrimental effects on organisms and has widespread effects on metabolism. Spermidine is an important member of the polyamines family and is involved in a range of abiotic stress responses in plants. Mitochondria play an essential role in cellular homeostasis and are key components of the stress response. Our results indicated that mitochondrial respiratory intensity increased by 80% in wild-type (WT) under heat stress, but the activities of key enzymes of the tricarboxylic acid (TCA) cycle and electron transport chain (ETC) were significantly reduced upon the knockdown of the spermidine synthase gene (). Furthermore, the content of mitochondrial pyruvate decreased by 36.1%, whereas the levels of free fatty acid increased by 28.8% under heat stress. Upon knockdown, the content of mitochondrial pyruvate was similar to that in the WT, but the medium-chain fatty acid (C6:0) decreased by 68.6%-84.2%, whereas the long-chain fatty acid (C18:2) marginally increased. Subsequent studies demonstrated that spermidine promoted the translation of long chain acyl-CoA dehydrogenase (LCAD) and mitochondrial trifunctional protein (MTP, also known as HADH), thereby enhancing fatty acid β-oxidation under heat stress. In conclusion, spermidine enhances key TCA cycle and ETC enzyme activities and is involved in heat stress-induced fatty acid β-oxidation by promoting the translation of LCAD and HADH, thereby improving the heat tolerance of .
Polyamines are stress-responsive molecules that enhance the tolerance of plants to multiple abiotic stresses by regulating a variety of biological processes. Our previous research indicated that heat stress induces the the biosynthesis of polyamines and promotes the conversion of putrescine to spermidine in , but the physiological role of elevated spermidine levels is yet to be elucidated. In this study, our findings demonstrated that spermidine enhances the heat tolerance in and that mitochondrial respiration is essential for spermidine-enhanced heat tolerance. This study elucidated a preliminary mechanism by which spermidine enhances heat tolerance of and provided a new insight into the understanding of how microorganisms resist heat stress.
高温是一种不可避免的环境胁迫，通常会对生物体产生有害影响，并对新陈代谢产生广泛影响。亚精胺是多胺家族的重要成员，参与植物的一系列非生物胁迫反应。线粒体在细胞稳态中起重要作用，是胁迫反应的关键组成部分。我们的结果表明，热胁迫下野生型（WT）的线粒体呼吸强度增加了80%，但在亚精胺合酶基因敲低后，三羧酸（TCA）循环和电子传递链（ETC）的关键酶活性显著降低。此外，热胁迫下线粒体丙酮酸含量降低了36.1%，而游离脂肪酸水平增加了28.8%。敲低后，线粒体丙酮酸含量与WT相似，但中链脂肪酸（C6:0）降低了68.6%-84.2%，而长链脂肪酸（C18:2）略有增加。随后的研究表明，亚精胺促进长链酰基辅酶A脱氢酶（LCAD）和线粒体三功能蛋白（MTP，也称为HADH）的翻译，从而增强热胁迫下的脂肪酸β-氧化。总之，亚精胺增强了关键的TCA循环和ETC酶活性，并通过促进LCAD和HADH的翻译参与热胁迫诱导的脂肪酸β-氧化，从而提高了的耐热性。
多胺是胁迫响应分子，通过调节多种生物过程增强植物对多种非生物胁迫的耐受性。我们之前的研究表明，热胁迫诱导多胺的生物合成并促进腐胺向亚精胺的转化，但亚精胺水平升高的生理作用尚待阐明。在本研究中，我们的发现表明亚精胺增强了的耐热性，并且线粒体呼吸对于亚精胺增强的耐热性至关重要。本研究阐明了亚精胺增强耐热性的初步机制，并为理解微生物如何抵抗热胁迫提供了新的见解。
