Pronounced differences between the native K+ channels and KAT1 and KST1 alpha-subunit homomers of guard cells.
Brüggemann L, Dietrich P, Dreyer I, Hedrich R (1999)
Publication Language: English
Publication Status: Published
Publication Type: Journal article, Original article
Publication year: 1999
Journal
Book Volume: 207
Pages Range: 370-6
Journal Issue: 3
Abstract
Stomatal opening is the result of K(+)-salt accumulation in guard cells. Potassium uptake in these motor cells is mediated by voltage-dependent, K(+)-selective ion channels. Here we compare the invitro properties of two guard-cell K(+)-channel alpha-subunits from Arabidopsis thaliana (L.) Heynh. (KAT1) and Solanum tuberosum L. (KST1) after heterologous expression with the respective K(+)-transport characteristics in their mother cell. The KAT1 and KST1 subunits when expressed in Xenopus oocytes shared the basic features of the K(+)-uptake channels in the corresponding guard cells, including voltage dependence and single-channel conductance. Besides these similarities, the electrophysiological comparison of K+ channels in the homologous and the heterologous expression systems revealed pronounced differences with respect to modulation and block by extracellular cations. In the presence of 1 mM Cs+, 50% of the guard-cell K(+)-uptake channels (GCKClin) in A. thaliana and S. tuberosum, were inhibited upon hyperpolarization to -90 mV. For a similar effect on KAT1 and KST1 in oocytes, voltages as negative as -155 mV were required. In contrast, compared to the K+ channels in vivo the functional alpha-subunit homomers almost lacked a voltage-dependent block by extracellular Ca2+. Similar to the block by Cs+ and Ca2+, the acid activation of the alpha-homomers was less pronounced in oocytes. Upon acidification the voltage-dependence shifted by 82 and 90 mV for GCKCLin in A. thaliana and S. tuberosum, respectively, but only by 25 mV for KAT1 and KST1. From the differences in K(+)-channel modulation in vivo and after heterologous expression we conclude that the properties of functional guard-cell K(+)-uptake channels result either from the heterometric assembly of different alpha-subunits or evolve from cell-type specific posttranslational modification.
Authors with CRIS profile
Involved external institutions
Germany (DE)How to cite
APA:
Brüggemann, L., Dietrich, P., Dreyer, I., & Hedrich, R. (1999). Pronounced differences between the native K+ channels and KAT1 and KST1 alpha-subunit homomers of guard cells. Planta, 207(3), 370-6.
MLA:
Brüggemann, Lioubov, et al. "Pronounced differences between the native K+ channels and KAT1 and KST1 alpha-subunit homomers of guard cells." Planta 207.3 (1999): 370-6.
BibTeX: Download