Zhu J K, Liu J, Xiong L
Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA.
Plant Cell. 1998 Jul;10(7):1181-91. doi: 10.1105/tpc.10.7.1181.
A large genetic screen for sos (for salt overly sensitive) mutants was performed in an attempt to isolate mutations in any gene with an sos phenotype. Our search yielded 28 new alleles of sos1, nine mutant alleles of a newly identified locus, SOS2, and one allele of a third salt tolerance locus, SOS3. The sos2 mutations, which are recessive, were mapped to the lower arm of chromosome V, approximately 2.3 centimorgans away from the marker PHYC. Growth measurements demonstrated that sos2 mutants are specifically hypersensitive to inhibition by Na+ or Li+ and not hypersensitive to general osmotic stresses. Interestingly, the SOS2 locus is also necessary for K+ nutrition because sos2 mutants were unable to grow on a culture medium with a low level of K+. The expression of several salt-inducible genes was superinduced in sos2 plants. The salt tolerance of sos1, sos2, and sos3 mutants correlated with their K+ tissue content but not their Na+ tissue content. Double mutant analysis indicated that the SOS genes function in the same pathway. Based on these results, a genetic model for salt tolerance mechanisms in Arabidopsis is presented in which SOS1, SOS2, and SOS3 are postulated to encode regulatory components controlling plant K+ nutrition that in turn is essential for salt tolerance.
为了分离出具有盐敏感（sos，salt overly sensitive）表型的任何基因中的突变，我们对sos突变体进行了大规模的遗传筛选。我们的研究找到了28个新的sos1等位基因、一个新鉴定基因座SOS2的9个突变等位基因以及第三个耐盐基因座SOS3的一个等位基因。隐性的sos2突变被定位到了第五条染色体的短臂上，距离标记PHYC约2.3厘摩。生长测量结果表明，sos2突变体对Na+或Li+的抑制作用具有特异性超敏感性，而对一般渗透胁迫不敏感。有趣的是，SOS2基因座对钾营养也是必需的，因为sos2突变体无法在低钾水平的培养基上生长。几个盐诱导基因的表达在sos2植株中被超诱导。sos1、sos2和sos3突变体的耐盐性与其钾离子组织含量相关，而与其钠离子组织含量无关。双突变分析表明，SOS基因在同一途径中发挥作用。基于这些结果，我们提出了一个拟南芥耐盐机制的遗传模型，其中SOS1、SOS2和SOS3被假定为编码控制植物钾营养的调控成分，而钾营养反过来对耐盐性至关重要。
