Essah Pauline A, Davenport Romola, Tester Mark
Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom.
Plant Physiol. 2003 Sep;133(1):307-18. doi: 10.1104/pp.103.022178.
Arabidopsis is frequently used as a genetic model in plant salt tolerance studies, however, its physiological responses to salinity remain poorly characterized. This study presents a characterization of initial Na+ entry and the effects of Ca2+ on plant growth and net Na+ accumulation in saline conditions. Unidirectional Na+ influx was measured carefully using very short influx times in roots of 12-d-old seedlings. Influx showed three components with distinct sensitivities to Ca2+, diethylpyrocarbonate, and osmotic pretreatment. Pharmacological agents and known mutants were used to test the contribution of different transport pathways to Na+ uptake. Influx was stimulated by 4-aminobutyric acid and glutamic acid; was inhibited by flufenamate, quinine, and cGMP; and was insensitive to modulators of K+ and Ca2+ channels. Influx did not differ from wild type in akt1 and hkt1 insertional mutants. These data suggested that influx was mediated by several different types of nonselective cation channels. Na+ accumulation in plants grown in 50 mM NaCl was strongly reduced by increasing Ca2+ activity (from 0.05-3.0 mM), and plant survival was improved. However, plant biomass was not affected by shoot Na+ concentration, suggesting that in Arabidopsis Na+ toxicity is not dependent on shoot Na+ accumulation. These data suggest that Arabidopsis is a good model for investigation of Na+ transport, but may be of limited utility as a model for the study of Na+ toxicity.
拟南芥经常被用作植物耐盐性研究中的遗传模型，然而，其对盐度的生理反应仍未得到充分表征。本研究描述了初始Na⁺进入情况以及Ca²⁺对盐胁迫条件下植物生长和净Na⁺积累的影响。使用12日龄幼苗的根，通过非常短的流入时间仔细测量单向Na⁺流入。流入显示出对Ca²⁺、焦碳酸二乙酯和渗透预处理具有不同敏感性的三个组分。使用药理试剂和已知突变体来测试不同转运途径对Na⁺吸收的贡献。4-氨基丁酸和谷氨酸刺激流入；氟灭酸、奎宁和cGMP抑制流入；并且对K⁺和Ca²⁺通道调节剂不敏感。在akt1和hkt1插入突变体中，流入与野生型没有差异。这些数据表明，流入是由几种不同类型的非选择性阳离子通道介导的。通过增加Ca²⁺活性（从0.05 - 3.0 mM），在50 mM NaCl中生长的植物中的Na⁺积累显著减少，并且植物存活率提高。然而，植物生物量不受地上部Na⁺浓度的影响，这表明在拟南芥中，Na⁺毒性不依赖于地上部Na⁺积累。这些数据表明，拟南芥是研究Na⁺转运的良好模型，但作为研究Na⁺毒性的模型，其效用可能有限。
