Perruc Elian, Charpenteau Martine, Ramirez Bertha Cecilia, Jauneau Alain, Galaud Jean-Philippe, Ranjeva Raoul, Ranty Benoît
Surfaces cellulaires et signalisation chez les végétaux, UMR 5546 CNRS/Université Paul Sabatier, Pôle de Biotechnologie Végétale, BP 17 Auzeville, 31326 Castanet-Tolosan Cedex, France.
Plant J. 2004 May;38(3):410-20. doi: 10.1111/j.1365-313X.2004.02062.x.
A clone for a novel Arabidopsisthaliana calmodulin (CaM)-binding protein of 25 kDa (AtCaMBP25) has been isolated by using a radiolabelled CaM probe to screen a cDNA expression library derived from A. thaliana cell suspension cultures challenged with osmotic stress. The deduced amino acid sequence of AtCaMBP25 contains putative nuclear localization sequences and shares significant degree of similarity with hypothetical plant proteins only. Fusion of the AtCaMBP25 coding sequence to reporter genes targets the hybrid protein to the nucleus. Bacterially expressed AtCaMBP25 binds, in a calcium-dependent manner, to a canonical CaM but not to a less conserved isoform of the calcium sensor. AtCaMBP25 is encoded by a single-copy gene, whose expression is induced in Arabidopsis seedlings exposed to dehydration, low temperature or high salinity. Transgenic plants overexpressing AtCaMBP25 exhibits an increased sensitivity to both ionic (NaCl) and non-ionic (mannitol) osmotic stress during seed germination and seedling growth. By contrast, transgenic lines expressing antisense AtCaMBP25 are significantly more tolerant to mannitol and NaCl stresses than the wild type. Thus, the AtCaMBP25 gene functions as a negative effector of osmotic stress tolerance and likely participates in stress signal transduction pathways.
通过使用放射性标记的钙调蛋白（CaM）探针筛选来自遭受渗透胁迫的拟南芥细胞悬浮培养物的cDNA表达文库，分离出了一种25 kDa的新型拟南芥钙调蛋白结合蛋白（AtCaMBP25）的克隆。AtCaMBP25推导的氨基酸序列包含假定的核定位序列，并且仅与假定的植物蛋白具有显著程度的相似性。AtCaMBP25编码序列与报告基因的融合将杂合蛋白靶向细胞核。细菌表达的AtCaMBP25以钙依赖的方式与典型的CaM结合，但不与钙传感器的保守性较低的同种型结合。AtCaMBP25由单拷贝基因编码，其表达在暴露于脱水、低温或高盐度的拟南芥幼苗中被诱导。在种子萌发和幼苗生长过程中，过表达AtCaMBP25的转基因植物对离子（NaCl）和非离子（甘露醇）渗透胁迫均表现出更高的敏感性。相比之下，表达反义AtCaMBP25的转基因株系比野生型对甘露醇和NaCl胁迫具有显著更高的耐受性。因此，AtCaMBP25基因作为渗透胁迫耐受性的负效应因子发挥作用，并可能参与胁迫信号转导途径。
