Llorente F, Oliveros J C, Martínez-Zapater J M, Salinas J
Departamento de Mejora Genética y Biotecnología, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Madrid, Spain.
Planta. 2000 Oct;211(5):648-55. doi: 10.1007/s004250000340.
To investigate the molecular mechanisms controlling the process of cold acclimation and to identify genes involved in plant freezing tolerance, mutations that impaired the cold acclimation capability of Arabidopsis thaliana (L.) Heynh were screened for. A new mutation, frs1 (freezing sensitive 1), that reduced both the constitutive freezing tolerance as well as the freezing tolerance of Arabidopsis after cold acclimation was characterized. This mutation also produced a wilty phenotype and excessive water loss. Plants with the frs1 mutation recovered their wild-type phenotype, their capability to tolerate freezing temperatures and their capability to retain water after an exogenous abscisic acid (ABA) treatment. Measurements of ABA revealed that frs1 mutants were ABA deficient, and complementation tests indicated that frs1 mutation was a new allele of the ABA3 locus showing that a mutation in this locus leads to an impairment of freezing tolerance. These results constitute the first report showing that a mutation in ABA3 leads to an impairment of freezing tolerance, and not only strengthen the conclusion that ABA is required for full development of freezing tolerance in cold-acclimated plants, but also demonstrate that ABA mediates the constitutive freezing tolerance of Arabidopsis. Gene expression in frs1 mutants was altered in response to dehydration, suggesting that freezing tolerance in Arabidopsis depends on ABA-regulated proteins that allow plants to survive the challenges imposed by subzero temperatures, mainly freeze-induced cellular dehydration.
为了研究控制冷驯化过程的分子机制并鉴定参与植物耐冻性的基因，我们筛选了影响拟南芥冷驯化能力的突变体。鉴定出一个新的突变体frs1（冻敏感1），它降低了拟南芥的组成型耐冻性以及冷驯化后的耐冻性。该突变还导致萎蔫表型和过度失水。用外源脱落酸（ABA）处理后，具有frs1突变的植株恢复了野生型表型、耐冻温度的能力和保水能力。ABA含量测定表明，frs1突变体缺乏ABA，互补试验表明frs1突变是ABA3位点的一个新等位基因，表明该位点的突变导致耐冻性受损。这些结果首次表明ABA3位点的突变导致耐冻性受损，不仅强化了ABA是冷驯化植物充分发展耐冻性所必需的这一结论，还证明ABA介导了拟南芥的组成型耐冻性。frs1突变体中的基因表达因脱水而改变，这表明拟南芥的耐冻性取决于ABA调节的蛋白质，这些蛋白质使植物能够应对零下温度带来的挑战，主要是冻害诱导的细胞脱水。
