Ding L, Zhu J K
Department of Plant Sciences, University of Arizona, Tucson 85721, USA.
Plant Physiol. 1997 Mar;113(3):795-9. doi: 10.1104/pp.113.3.795.
Sos1 is an Arabidopsis thaliana mutant with > 20 times higher sensitivity toward Na+ inhibition due to a defective high-affinity potassium-uptake system. We report here that sos1 accumulates less Na+ than the wild type in response to NaCl stress. The Na+ contents in sos1 seedlings exposed to 25 mM NaCl for 2 or more d are about 43% lower than those in the wild type. When assayed at 20 mM external NaCl, sos1 seedlings pretreated with low potassium have 32% lower Na+ uptake than the wild type. However, little difference in Na+ uptake could be measured when the seedlings were not pretreated with low potassium. Low-potassium treatment was shown to induce high-affinity potassium-uptake activity in Arabidopsis seedlings. No substantial difference in Na+ efflux between sos1 and the wild type was detected. The results show that the reduced Na+ accumulation in sos1 is due to a lower Na+ influx rate. Therefore, the sos1 mutation appears to disrupt low-affinity Na+ uptake in addition to its impairment of high-affinity K+ uptake.
Sos1是一种拟南芥突变体，由于其高亲和力钾吸收系统存在缺陷，对Na+抑制的敏感性比野生型高20倍以上。我们在此报告，在NaCl胁迫下，sos1积累的Na+比野生型少。暴露于25 mM NaCl 2天或更长时间的sos1幼苗中的Na+含量比野生型低约43%。在20 mM外部NaCl条件下测定时，用低钾预处理的sos1幼苗的Na+吸收比野生型低32%。然而，当幼苗未用低钾预处理时，未检测到Na+吸收有显著差异。低钾处理被证明可诱导拟南芥幼苗的高亲和力钾吸收活性。未检测到sos1和野生型之间的Na+外流有实质性差异。结果表明，sos1中Na+积累减少是由于较低的Na+内流速率。因此，sos1突变除了损害高亲和力K+吸收外，似乎还破坏了低亲和力Na+吸收。
