Université d'Angers, INRA, Agrocampus-Ouest, UMR1191 Physiologie Moléculaire des Semences, 16 Bd Lavoisier, F-49045 Angers, France.
Plant Cell Environ. 2010 Mar;33(3):418-30. doi: 10.1111/j.1365-3040.2009.02093.x. Epub 2009 Nov 25.
Late embryogenesis-abundant (LEA) proteins are one of the components involved in desiccation tolerance (DT) by maintaining cellular structures in the dry state. Among them, MtPM25, a member of the group 5 is specifically associated with DT in Medicago truncatula seeds. Its function is unknown and its classification as a LEA protein remains elusive. Here, evidence is provided that MtPM25 is a hydrophobic, intrinsically disordered protein that shares the characteristics of canonical LEA proteins. Screening protective activities by testing various substrates against freezing, heating and drying indicates that MtPM25 is unable to protect membranes but able to prevent aggregation of proteins during stress. Prevention of aggregation was also found for the water soluble proteome of desiccation-sensitive radicles. This inhibition was significantly higher than that of MtEM6, one of the most hydrophilic LEA protein associated with DT. Moreover, when added after the stress treatment, MtPM25 is able to rapidly dissolve aggregates in a non-specific manner. Sorption isotherms show that when it is unstructured, MtPM25 absorbs up to threefold more water than MtEM6. MtPM25 is likely to act as a protective molecule during drying and plays an additional role as a repair mechanism compared with other LEA proteins.
晚期胚胎丰富蛋白（LEA）是参与干燥耐受性（DT）的组成部分之一，通过在干燥状态下维持细胞结构。其中，MtPM25 是 Medicago truncatula 种子中与 DT 特异性相关的第 5 组的成员。其功能未知，其 LEA 蛋白的分类仍不清楚。本文提供的证据表明，MtPM25 是一种疏水性、无规卷曲的蛋白质，具有典型的 LEA 蛋白的特征。通过测试各种基质对冷冻、加热和干燥的保护活性表明，MtPM25 不能保护膜，但能够防止应激时蛋白质的聚集。还发现脱水敏感的根毛水溶蛋白组在脱水过程中发生聚集抑制，其抑制作用明显高于与 DT 相关的最亲水的 LEA 蛋白之一 MtEM6。此外，当在应激处理后添加时，MtPM25 能够以非特异性的方式迅速溶解聚集体。吸附等温线表明，当它处于无规卷曲状态时，MtPM25 吸收的水分比 MtEM6 多三倍。与其他 LEA 蛋白相比，MtPM25 可能在干燥过程中作为一种保护分子发挥作用，并作为一种修复机制发挥额外的作用。
