Poster: Stomatal Physiology
Abs #
387: The reported blue light-stimulated opening of the zeaxanthin-less mutant, npq1, is phytochrome-mediated.
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Presenter: |
Talbott, Lawrence D., ltalbott@biology.ucla.edu |
Authors | Talbott, Lawrence D. (A) Shmayevich, Irene (A) Chung, Yooshun (A) Zeiger, Eduardo (A) | | Affiliations: |
(A): Dept. of Organismal Biology, Ecology and Evolution. University of California, Los Angeles
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A study showing that guard cells from npq1, a zeaxanthin-less Arabidopsis mutant, lack a specific blue light response provides evidence for a role of zeaxanthin in blue light photoreception of guard cells. Recent studies documenting blue light opening of npq1 guard cells questioned that conclusion. We report here a study characterizing this opening as a non-specific light response of npq1. Red light (photosynthetic)-mediated opening in both wt and npq1 epidermal strips saturated at 100 mmol m-2 s-1. Under this saturating red light, wt stomata opened in response to 10 mmol m-2 s-1 blue light but npq1 stomata did not. In contrast, both wt and npq1 stomata under 50 mmol m-2 s-1 red light opened in response to blue light. This blue light opening was fully reversed in npq1 but not in wt by simultaneous irradiation with far-red light. Addition of 10 mmol m-2 s-1 red light to 50 mmol m-2 s-1 background red light was equally effective in causing a far red-reversible opening in npq1. The dose response curve for red light-stimulated opening in npq1 was biphasic showing a minor peak at 20 mmol m-2 s-1. This minor peak was eliminated by far red light. In contrast, the dose response curve for red light-stimulated opening in wt stomata was monophasic and showed no far red light effect at any red light fluence rate. We conclude that: 1) The lack of zeaxanthin in the guard cell chloroplasts of npq1 elicits a phytochrome-mediated opening that is absent in wt stomata. 2) As recently reported for stomata of the orchid, Paphiopedilum, the phytochrome response is maximal at low fluence rates of red light and absent under saturating red light. 3) The blue light stimulated opening of wt stomata is a blue light-specific response whereas in npq1 it is phytochrome response.
