Kamble Nitin Uttam, Majee Manoj
MM203 Seed and Stress Biology Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi 110067, India.
Development. 2022 Jun 1;149(11). doi: 10.1242/dev.200600. Epub 2022 Jun 10.
In contrast to desiccation-tolerant orthodox seeds, recalcitrant seeds are desiccation sensitive and are unable to survive for a prolonged time. Here, our analyses of Oryza species with contrasting seed desiccation tolerance reveals that PROTEIN L-ISOASPARTYL METHYLTRANSFERASE (PIMT), an enzyme that repairs abnormal isoaspartyl (isoAsp) residues in proteins, acts as a key player that governs seed desiccation tolerance to orthodox seeds but is ineffective in recalcitrant seeds. We observe that, unlike the orthodox seed of Oryza sativa, desiccation intolerance of the recalcitrant seeds of Oryza coarctata are linked to reduced PIMT activity and increased isoAsp accumulation due to the lack of coordinated action of ABA and ABI transcription factors to upregulate PIMT during maturation. We show that suppression of PIMT reduces, and its overexpression increases, seed desiccation tolerance and seed longevity in O. sativa. Our analyses further reveal that the ABI transcription factors undergo isoAsp formation that affect their functional competence; however, PIMT interacts with and repairs isoAsp residues and facilitates their functions. Our results thus illustrate a new insight into the mechanisms of acquisition of seed desiccation tolerance and longevity by ABI transcription factors and the PIMT module.
与耐干燥的传统种子不同，顽拗性种子对干燥敏感，无法长时间存活。在此，我们对种子干燥耐受性不同的稻属物种进行分析，结果表明，蛋白质L-异天冬氨酰甲基转移酶（PIMT），一种修复蛋白质中异常异天冬氨酰（isoAsp）残基的酶，是决定传统种子干燥耐受性的关键因素，但对顽拗性种子无效。我们观察到，与栽培稻的传统种子不同，窄叶野生稻顽拗性种子的干燥不耐受与PIMT活性降低和isoAsp积累增加有关，这是由于在种子成熟过程中脱落酸（ABA）和ABI转录因子缺乏协同作用来上调PIMT。我们发现，抑制PIMT会降低栽培稻种子的干燥耐受性和种子寿命，而过表达PIMT则会提高其干燥耐受性和种子寿命。我们的分析进一步揭示，ABI转录因子会形成影响其功能能力的isoAsp残基；然而，PIMT与isoAsp残基相互作用并进行修复，从而促进其功能。因此，我们的研究结果为ABI转录因子和PIMT模块在种子获得干燥耐受性和寿命的机制方面提供了新的见解。
