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Proc Natl Acad Sci U S A. 2016 Aug 30;113(35):E5242-9. doi: 10.1073/pnas.1519555113. Epub 2016 Aug 15.

Rapid hyperosmotic-induced Ca2+ responses in Arabidopsis thaliana exhibit sensory potentiation and involvement of plastidial KEA transporters.

Author information

1
Division of Biological Sciences, Cell and Developmental Biology Section, Food and Fuel for the 21st Century Center, University of California, San Diego, La Jolla, CA 92093;
2
Division of Biological Sciences, Cell and Developmental Biology Section, Food and Fuel for the 21st Century Center, University of California, San Diego, La Jolla, CA 92093; School of Biological Sciences, Washington State University, Pullman, WA 99164.
3
Division of Biological Sciences, Cell and Developmental Biology Section, Food and Fuel for the 21st Century Center, University of California, San Diego, La Jolla, CA 92093; jischroeder@ucsd.edu.

Abstract

Plants experience hyperosmotic stress when faced with saline soils and possibly with drought stress, but it is currently unclear how plant roots perceive this stress in an environment of dynamic water availabilities. Hyperosmotic stress induces a rapid rise in intracellular Ca(2+) concentrations ([Ca(2+)]i) in plants, and this Ca(2+) response may reflect the activities of osmo-sensory components. Here, we find in the reference plant Arabidopsis thaliana that the rapid hyperosmotic-induced Ca(2+) response exhibited enhanced response magnitudes after preexposure to an intermediate hyperosmotic stress. We term this phenomenon "osmo-sensory potentiation." The initial sensing and potentiation occurred in intact plants as well as in roots. Having established a quantitative understanding of wild-type responses, we investigated effects of pharmacological inhibitors and candidate channel/transporter mutants. Quintuple mechano-sensitive channels of small conductance-like (MSL) plasma membrane-targeted channel mutants as well as double mid1-complementing activity (MCA) channel mutants did not affect the response. Interestingly, however, double mutations in the plastid K(+) exchange antiporter (KEA) transporters kea1kea2 and a single mutation that does not visibly affect chloroplast structure, kea3, impaired the rapid hyperosmotic-induced Ca(2+) responses. These mutations did not significantly affect sensory potentiation of the response. These findings suggest that plastids may play an important role in early steps mediating the response to hyperosmotic stimuli. Together, these findings demonstrate that the plant osmo-sensory components necessary to generate rapid osmotic-induced Ca(2+) responses remain responsive under varying osmolarities, endowing plants with the ability to perceive the dynamic intensities of water limitation imposed by osmotic stress.

KEYWORDS:

abscisic acid; calcium; osmotic sensing; plastid; salt stress

PMID:
27528686
PMCID:
PMC5024618
[Available on 2017-02-28]
DOI:
10.1073/pnas.1519555113
[Indexed for MEDLINE]
Free PMC Article

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