Zhang Wei, Zhou Ren-Gang, Gao Ying-Jie, Zheng Shu-Zhi, Xu Peng, Zhang Su-Qiao, Sun Da-Ye
Institute of Molecular Cell Biology, Hebei Normal University, Shijiazhuang 050016, China.
Plant Physiol. 2009 Apr;149(4):1773-84. doi: 10.1104/pp.108.133744. Epub 2009 Feb 11.
Heat shock (HS) is a common form of stress suffered by plants. It has been proposed that calmodulin (CaM) is involved in HS signal transduction, but direct evidence has been lacking. To investigate the potential regulatory function of CaM in the HS signal transduction pathway, T-DNA knockout mutants for AtCaM2, AtCaM3, and AtCaM4 were obtained and their thermotolerance tested. Of the three knockout mutant plants, there were no differences compared with wild-type plants under normal conditions. However, the AtCaM3 knockout mutant showed a clear reduction in thermotolerance after heat treatment at 45 degrees C for 50 min. Overexpression of AtCaM3 in either the AtCaM3 knockout or wild-type background significantly rescued or increased the thermotolerance, respectively. Results from electrophoretic mobility-shift assays, real-time quantitative reverse transcription-polymerase chain reaction, and western-blot analyses revealed that, after HS, the DNA-binding activity of HS transcription factors, mRNA transcription of HS protein genes, and accumulation of HS protein were down-regulated in the AtCaM3 knockout mutant and up-regulated in the AtCaM3-overexpressing transgenic lines. Taken together, these results suggest that endogenous AtCaM3 is a key component in the Ca2+-CaM HS signal transduction pathway.
热激（HS）是植物遭受的一种常见胁迫形式。有人提出钙调蛋白（CaM）参与热激信号转导，但一直缺乏直接证据。为了研究CaM在热激信号转导途径中的潜在调节功能，获得了AtCaM2、AtCaM3和AtCaM4的T-DNA敲除突变体，并对其耐热性进行了测试。在这三种敲除突变体植株中，正常条件下与野生型植株相比没有差异。然而，AtCaM3敲除突变体在45℃热处理50分钟后耐热性明显降低。在AtCaM3敲除或野生型背景中过表达AtCaM3分别显著挽救或提高了耐热性。电泳迁移率变动分析、实时定量逆转录-聚合酶链反应和蛋白质免疫印迹分析结果表明，热激后，AtCaM3敲除突变体中热激转录因子的DNA结合活性、热激蛋白基因的mRNA转录以及热激蛋白的积累均下调，而在AtCaM3过表达转基因株系中上调。综上所述，这些结果表明内源性AtCaM3是Ca2+-CaM热激信号转导途径中的关键组分。
