Central functions of bicarbonate in S-type anion channel activation and OST1 protein kinase in CO 2 signal transduction in guard cell

Type
Article

Authors
Xue, Shaowu
Hu, Honghong
Ries, Amber
Merilo, Ebe
Kollist, Hannes
Schroeder, Julian I

KAUST Grant Number
KUS-F1-021-31

Online Publication Date
2011-03-18

Print Publication Date
2011-04-20

Date
2011-03-18

Abstract
Plants respond to elevated CO(2) via carbonic anhydrases that mediate stomatal closing, but little is known about the early signalling mechanisms following the initial CO(2) response. It remains unclear whether CO(2), HCO(3)(-) or a combination activates downstream signalling. Here, we demonstrate that bicarbonate functions as a small-molecule activator of SLAC1 anion channels in guard cells. Elevated intracellular HCO(3)(-) with low [CO(2)] and [H(+)] activated S-type anion currents, whereas low HCO(3)(-) at high [CO(2)] and [H(+)] did not. Bicarbonate enhanced the intracellular Ca(2+) sensitivity of S-type anion channel activation in wild-type and ht1-2 kinase mutant guard cells. ht1-2 mutant guard cells exhibited enhanced bicarbonate sensitivity of S-type anion channel activation. The OST1 protein kinase has been reported not to affect CO(2) signalling. Unexpectedly, OST1 loss-of-function alleles showed strongly impaired CO(2)-induced stomatal closing and HCO(3)(-) activation of anion channels. Moreover, PYR/RCAR abscisic acid (ABA) receptor mutants slowed but did not abolish CO(2)/HCO(3)(-) signalling, redefining the convergence point of CO(2) and ABA signalling. A new working model of the sequence of CO(2) signalling events in gas exchange regulation is presented.

Citation
Xue S, Hu H, Ries A, Merilo E, Kollist H, et al. (2011) Central functions of bicarbonate in S-type anion channel activation and OST1 protein kinase in CO 2 signal transduction in guard cell . The EMBO Journal 30: 1645–1658. Available: http://dx.doi.org/10.1038/emboj.2011.68.

Acknowledgements
We thank Dr Cawas Engineer and Dr Rama Vaidyanathan for critical reading of the manuscript and Dr Kristiina Laanements for confirmation of whole-plant gas exchange data in the Ler ost1 mutants. We also thank Drs Nan Sang, Yanxi Pei and Shuqing Zhao for help during revision of the manuscript. This work was supported by grants from the National Science Foundation (MCB0918220), the National Institutes of Health (GM060396), Bayer Crop Sciences, the Chemical Sciences, Geosciences, and Biosciences Division of the Office of Basic Energy Sciences at the US Department of Energy (DOE-DE-FG02-03ER15449) and the Human Frontiers in Science Program to JIS and a fellowship from the King Abdullah University of Science and Technology (KAUST; No. KUS-F1-021-31) to HH, and in part supported by grants from the National Science Foundation of China (20701028) to SX and from the Estonian Science Foundation 7763 and SF0180071S07 to HK.

Publisher
Wiley

Journal
The EMBO Journal

DOI
10.1038/emboj.2011.68

PubMed ID
21423149

PubMed Central ID
PMC3102275

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