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Millisecond UV‐B irradiation evokes prolonged elevation of cytosolic‐free Ca2+ and stimulates gene expression in transgenic parsley cell cultures

Millisecond UV‐B irradiation evokes prolonged elevation of cytosolic‐free Ca2+ and stimulates... Chalcone synthase (CHS) is a key enzyme leading to the generation of protective flavonoids in plants under environmental stress. Expression of the CHS gene is strongly upregulated by exposures to UV light, a response also observed in heterotrophic parsley cell cultures. Although there are hints that the stimulus for CHS expression may be coupled to UV‐B irradiation through a rise in cytosolic‐free Ca2+ ([Ca2+]i), the temporal relationship of these events has never been investigated critically. To explore this question, we have used a CHS promoter/luciferase (CHS/LUC) reporter gene fusion and recorded its expression and [Ca2+]i elevation in a transgenic parsley cell culture following millisecond light pulses. Luciferase expression was enhanced maximally seven‐ (± 2) fold by 30 10 ms flashes of UV‐B light. The response was specific to wavelengths of 300–330 nm and could be inhibited in the presence of the Ca2+ channel blocker nifedipine. In parallel measurements, using Fura‐2 fluorescence ratio microphotometry, we found that 10 ms UV‐B flashes also evoked a gradual and prolonged rise of [Ca2+]i in the parsley cells which was irreversible within the timescale of these experiments, but could be prevented by prior treatment with nifedipine. These, and additional results, indicate a remarkably high temporal sensitivity to, and specificity for, UV‐B light in CHS gene expression independent of UV‐mediated DNA damage by thymine dimerization. The ability of transient UV‐B stimulation to evoke prolonged elevations of [Ca2+]i suggests a functional coupling between the initial light stimulus and subsequent gene expression that takes place many tens of minutes later. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Plant Journal Wiley

Millisecond UV‐B irradiation evokes prolonged elevation of cytosolic‐free Ca2+ and stimulates gene expression in transgenic parsley cell cultures

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References (57)

Publisher
Wiley
Copyright
Copyright © 1999 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0960-7412
eISSN
1365-313X
DOI
10.1046/j.1365-313X.1999.00584.x
Publisher site
See Article on Publisher Site

Abstract

Chalcone synthase (CHS) is a key enzyme leading to the generation of protective flavonoids in plants under environmental stress. Expression of the CHS gene is strongly upregulated by exposures to UV light, a response also observed in heterotrophic parsley cell cultures. Although there are hints that the stimulus for CHS expression may be coupled to UV‐B irradiation through a rise in cytosolic‐free Ca2+ ([Ca2+]i), the temporal relationship of these events has never been investigated critically. To explore this question, we have used a CHS promoter/luciferase (CHS/LUC) reporter gene fusion and recorded its expression and [Ca2+]i elevation in a transgenic parsley cell culture following millisecond light pulses. Luciferase expression was enhanced maximally seven‐ (± 2) fold by 30 10 ms flashes of UV‐B light. The response was specific to wavelengths of 300–330 nm and could be inhibited in the presence of the Ca2+ channel blocker nifedipine. In parallel measurements, using Fura‐2 fluorescence ratio microphotometry, we found that 10 ms UV‐B flashes also evoked a gradual and prolonged rise of [Ca2+]i in the parsley cells which was irreversible within the timescale of these experiments, but could be prevented by prior treatment with nifedipine. These, and additional results, indicate a remarkably high temporal sensitivity to, and specificity for, UV‐B light in CHS gene expression independent of UV‐mediated DNA damage by thymine dimerization. The ability of transient UV‐B stimulation to evoke prolonged elevations of [Ca2+]i suggests a functional coupling between the initial light stimulus and subsequent gene expression that takes place many tens of minutes later.

Journal

The Plant Journal – Wiley

Published: Oct 1, 1999

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