Polyamines improve K+/Na+ homeostasis in barley seedlings by regulating root ion channel activities.
Polyamines are known to increase in plant cells in response to a variety of stress conditions. However, the physiological roles of elevated polyamines are not understood well. Here we investigated the effects of polyamines on ion channel activities by applying patch-clamp techniques to protoplasts derived from barley (Hordeum vulgare) seedling root cells. Extracellular application of polyamines significantly blocked the inward Na(+) and K(+) currents (especially Na(+) currents) in root epidermal and cortical cells. These blocking effects of polyamines were increased with increasing polycation charge. In root xylem parenchyma, the inward K(+) currents were blocked by extracellular spermidine, while the outward K(+) currents were enhanced. At the whole-plant level, the root K(+) content, as well as the root and shoot Na(+) levels, was decreased significantly by exogenous spermidine. Together, by restricting Na(+) influx into roots and by preventing K(+) loss from shoots, polyamines were shown to improve K(+)/Na(+) homeostasis in barley seedlings. It is reasonable to propose that, therefore, elevated polyamines under salt stress should be a self-protecting response for plants to combat detrimental consequences resulted from imbalance of Na(+) and K(+).
Zhao
Fugeng
F
School of Life Sciences, Nanjing University, Nanjing 210039, China. fgzhao@nju.edu.cn
Song
Chun-Peng
CP
He
Jiaqian
J
Zhu
Hui
H
D006706:Homeostasis / Q000187:drug effects; D001467:Hordeum / Q000187:drug effects* / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials; D018517:Plant Roots / Q000187:drug effects* / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D011073:Polyamines / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism*; D011523:Protoplasts / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013095:Spermidine / Q000494:pharmacology*
D007473:Ion Channels; D011073:Polyamines; D012964:Sodium; D011188:Potassium; D013095:Spermidine