Rice Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, China.
Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fuzhou, Fujian, China.
Plant Mol Biol. 2015 Nov;89(4-5):475-92. doi: 10.1007/s11103-015-0383-1. Epub 2015 Oct 5.
Damaged proteins containing abnormal isoaspartyl (isoAsp) accumulate as seeds age and the abnormality is thought to undermine seed vigor. Protein-L-isoaspartyl methyltransferase (PIMT) is involved in isoAsp-containing protein repair. Two PIMT genes from rice (Oryza sativa L.), designated as OsPIMT1 and OsPIMT2, were isolated and investigated for their roles. The results indicated that OsPIMT2 was mainly present in green tissues, but OsPIMT1 largely accumulated in embryos. Confocal visualization of the transient expression of OsPIMTs showed that OsPIMT2 was localized in the chloroplast and nucleus, whereas OsPIMT1 was predominately found in the cytosol. Artificial aging results highlighted the sensitivity of the seeds of OsPIMT1 mutant line when subjected to accelerated aging. Overexpression of OsPIMT1 in transgenic seeds reduced the accumulation of isoAsp-containing protein in embryos, and increased embryo viability. The germination percentage of transgenic seeds overexpressing OsPIMT1 increased 9-15% compared to the WT seeds after 21-day of artificial aging, whereas seeds from the OsPIMT1 RNAi lines overaccumulated isoAsp in embryos and experienced rapid loss of seed germinability. Taken together, these data strongly indicated that OsPIMT1-related seed longevity improvement is probably due to the repair of detrimental isoAsp-containing proteins that over accumulate in embryos when subjected to accelerated aging.
含有异常异天冬氨酸（isoAsp）的受损蛋白质会随着种子的衰老而积累，并且这种异常被认为会破坏种子活力。蛋白-L-异天冬氨酸甲基转移酶（PIMT）参与含有异天冬氨酸的蛋白质修复。从水稻（Oryza sativa L.）中分离出两种 PIMT 基因，分别命名为 OsPIMT1 和 OsPIMT2，并研究了它们的作用。结果表明，OsPIMT2 主要存在于绿色组织中，而 OsPIMT1 则主要在胚胎中积累。OsPIMTs 的瞬时表达的共聚焦可视化显示，OsPIMT2 定位于叶绿体和细胞核中，而 OsPIMT1 主要存在于细胞质中。人工老化结果突出了 OsPIMT1 突变体系种子在加速老化时的敏感性。在转基因种子中过表达 OsPIMT1 可减少胚胎中含有异天冬氨酸的蛋白质的积累，并提高胚胎活力。与 WT 种子相比，过表达 OsPIMT1 的转基因种子在人工老化 21 天后的发芽率提高了 9-15%，而 OsPIMT1 RNAi 系的种子在胚胎中积累过多的异天冬氨酸，并且种子活力迅速丧失。总之，这些数据强烈表明，OsPIMT1 相关的种子长寿改善可能是由于加速老化时胚胎中积累的有害含有异天冬氨酸的蛋白质的修复。
