College of Grassland Science and Technology, Sichuan Agricultural University, Chengdu, 611130, China.
Plant J. 2023 Jul;115(2):369-385. doi: 10.1111/tpj.16230. Epub 2023 Apr 21.
Maintenance of stable mitochondrial respiratory chains could enhance adaptability to high temperature, but the potential mechanism was not elucidated clearly in plants. In this study, we identified and isolated a TrFQR1 gene encoding the flavodoxin-like quinone reductase 1 (TrFQR1) located in mitochondria of leguminous white clover (Trifolium repens). Phylogenetic analysis indicated that amino acid sequences of FQR1 in various plant species showed a high degree of similarities. Ectopic expression of TrFQR1 protected yeast (Saccharomyces cerevisiae) from heat damage and toxic levels of benzoquinone, phenanthraquinone and hydroquinone. Transgenic Arabidopsis thaliana and white clover overexpressing TrFQR1 exhibited significantly lower oxidative damage and better photosynthetic capacity and growth than wild-type in response to high-temperature stress, whereas AtFQR1-RNAi A. thaliana showed more severe oxidative damage and growth retardation under heat stress. TrFQR1-transgenic white clover also maintained better respiratory electron transport chain than wild-type plants, as manifested by significantly higher mitochondrial complex II and III activities, alternative oxidase activity, NAD(P)H content, and coenzyme Q10 content in response to heat stress. In addition, overexpression of TrFQR1 enhanced the accumulation of lipids including phosphatidylglycerol, monogalactosyl diacylglycerol, sulfoquinovosyl diacylglycerol and cardiolipin as important compositions of bilayers involved in dynamic membrane assembly in mitochondria or chloroplasts positively associated with heat tolerance. TrFQR1-transgenic white clover also exhibited higher lipids saturation level and phosphatidylcholine:phosphatidylethanolamine ratio, which could be beneficial to membrane stability and integrity during a prolonged period of heat stress. The current study proves that TrFQR1 is essential for heat tolerance associated with mitochondrial respiratory chain, cellular reactive oxygen species homeostasis, and lipids remodeling in plants. TrFQR1 could be selected as a key candidate marker gene to screen heat-tolerant genotypes or develop heat-tolerant crops via molecular-based breeding.
维持稳定的线粒体呼吸链可以增强植物对高温的适应能力，但其中的潜在机制尚不清楚。本研究鉴定并分离了一个编码黄素蛋白样醌还原酶 1（TrFQR1）的 TrFQR1 基因，该基因位于豆科白三叶草（Trifolium repens）的线粒体中。系统发育分析表明，不同植物物种的 FQR1 氨基酸序列具有高度相似性。异位表达 TrFQR1 可保护酵母（酿酒酵母）免受热损伤和醌、蒽醌和氢醌的毒性水平的影响。过表达 TrFQR1 的转基因拟南芥和白三叶草在高温胁迫下表现出较低的氧化损伤、更好的光合作用和生长能力，而 AtFQR1-RNAi 拟南芥在热胁迫下表现出更严重的氧化损伤和生长迟缓。TrFQR1 转基因白三叶草在响应高温胁迫时，线粒体复合物 II 和 III 活性、交替氧化酶活性、NAD(P)H 含量和辅酶 Q10 含量也显著高于野生型，这表明 TrFQR1 转基因白三叶草的呼吸电子传递链也得到了更好的维持。此外，过表达 TrFQR1 可正向促进脂质（包括磷脂酰甘油、单半乳糖二酰甘油、磺基奎诺二酰甘油和心磷脂）的积累，这些脂质是线粒体或叶绿体中双层膜动态组装的重要组成部分，与耐热性呈正相关。TrFQR1 转基因白三叶草还表现出更高的脂质饱和度和磷脂酰胆碱：磷脂酰乙醇胺比值，这有利于在长时间的热胁迫下保持膜的稳定性和完整性。本研究证明，TrFQR1 对于与线粒体呼吸链、细胞活性氧平衡和植物脂质重塑相关的耐热性至关重要。TrFQR1 可作为关键候选标记基因，通过分子育种筛选耐热基因型或培育耐热作物。
