کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8357227 | 1542046 | 2016 | 9 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
How high do ion fluxes go? A re-evaluation of the two-mechanism model of K+ transport in plant roots
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کلمات کلیدی
موضوعات مرتبط
علوم زیستی و بیوفناوری
علوم کشاورزی و بیولوژیک
دانش گیاه شناسی
پیش نمایش صفحه اول مقاله

چکیده انگلیسی
Potassium (K+) acquisition in roots is generally described by a two-mechanism model, consisting of a saturable, high-affinity transport system (HATS) operating via H+/K+ symport at low (<1Â mM) external [K+] ([K+]ext), and a linear, low-affinity system (LATS) operating via ion channels at high (>1Â mM) [K+]ext. Radiotracer measurements in the LATS range indicate that the linear rise in influx continues well beyond nutritionally relevant concentrations (>10Â mM), suggesting K+ transport may be pushed to extraordinary, and seemingly limitless, capacity. Here, we assess this rise, asking whether LATS measurements faithfully report transmembrane fluxes. Using 42K+-isotope and electrophysiological methods in barley, we show that this flux is part of a K+-transport cycle through the apoplast, and masks a genuine plasma-membrane influx that displays Michaelis-Menten kinetics. Rapid apoplastic cycling of K+ is corroborated by an absence of transmembrane 42K+ efflux above 1Â mM, and by the efflux kinetics of PTS, an apoplastic tracer. A linear apoplastic influx, masking a saturating transmembrane influx, was also found in Arabidopsis mutants lacking the K+ transporters AtHAK5 and AtAKT1. Our work significantly revises the model of K+ transport by demonstrating a surprisingly modest upper limit for plasma-membrane influx, and offers insight into sodium transport under salt stress.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Plant Science - Volume 243, February 2016, Pages 96-104
Journal: Plant Science - Volume 243, February 2016, Pages 96-104
نویسندگان
Devrim Coskun, Dev T. Britto, Leon V. Kochian, Herbert J. Kronzucker,