Sensory Transduction of the CO2 Response of Guard Cells
Stomata have a key role in the regulation of gas exchange and intercellular CO2 concentrations of leaves. Guard cells sense internal and external signals in the leaf environment and transduce these signals into osmoregulatory processes that control stomatal apertures. This research proposal addresses the characterization of the sensory transduction of the CO2 signal in guard cells. Recent studies have shown that in Vicia leaves kept at constant light and temperature in a growth chamber, changes in ambient CO2 concentrations cause large changes in guard cell zeaxanthin that are linear with CO2-dependent changes in stomatal apertures. Research proposed here will test the hypothesis that zeaxanthin function as a transducer of CO2 signals in guard cells. Three central aspects of this hypothesis will be investigated: CO2 sensing by the carboxylation reaction of Rubisco in the guard cell chloroplast, which would modulate zeaxanthin concentrations via changes in lumen pH; transduction of the CO2 signal by zeaxanthin via a transducing cascade that controls guard cell osmoregulation; and blue light dependence of the CO2 signal transduction by zeaxanthin, required for the formation of an isomeric form of zeaxanthin that is physiologically active as a transducer. The role of Rubisco in CO2 sensing will be investigated in experiments characterizing the stomatal response to CO2 in the Arabidopsis mutants R100 and rca-, which have reduced rates of Rubisco-dependent carboxylation. The role of zeaxanthin as a CO2 transducer will be studied in npq1, a zeaxanthin-less mutant. The blue light-dependence of CO2 sensing will be studied in experiments characterizing the stomatal response to CO2 under red light. Arabidopsis mutants will also be used in further studies of an acclimation of the stomatal response to CO2, and a possible role of the xanthophyll cycle of the guard cell chloroplast in acclimations of the stomatal response to CO2. Studies on the osmoregulatory role of sucrose in the stomatal response to CO2 will investigate downstream targets of the CO2 response. Success in characterizing a zeaxanthin-dependent CO2 sensing mechanism in guard cells will significantly enhance our understanding of stomatal function and CO2 sensing in plants cells. Further characterization of guard cells acclimation to CO2 should enrich our understanding of plant acclimations and adaptations to their environment, and of possible effects of elevated atmospheric CO2 concentrations on the vegetation.
- Research Organization:
- Univ. of California, Los Angeles, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- FG03-90ER20011
- OSTI ID:
- 840963
- Country of Publication:
- United States
- Language:
- English
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