Role of zeaxanthin in blue light photoreception and the modulation of light-CO2 interactions in guard cells
1998
Zeiger, E. | Zhu, J.
The stomatal response to blue light is an intrinsic component of the sensory transducing processes mediating light-stimulated stomatal movements. Guard cell chloroplasts have a specific blue light response with an action spectrum that resembles the action spectrum for blue light-stimulated stomatal opening, suggesting a role of guard cell chloroplasts in the sensory transduction of blue light. The xanthophyll, zeaxanthin has recently been identified as a blue light photoreceptor in guard cells. The inhibitor of zeaxanthin formation, dithiothreitol, inhibits zeaxanthin formation and the stomatal response to blue light in a concentration-dependent fashion. In greenhouse-grown leaves, guard cell zeaxanthin content closely tracks incident radiation and it is positively correlated with stomatal apertures. The sensitivity of guard cells to blue light co-varies with guard cell zeaxanthin content. A zeaxanthin-less mutant of Arabidopsis is devoid of a typical stomatal response to blue light. At constant light and temperature, changes in ambient [CO2] in a growth chamber caused large changes in stomata aperture and in guard cell zeaxanthin. The aperture-zeaxanthin changes were linearly related over a wide range of [CO2]. Experiments with detached epidermis showed a similar relation among [CO2], stomatal apertures and guard cell zeaxanthin, and DTT inhibited the CO2 response in the light without altering the CO2 response in the dark. These results indicate that blue light sensing by guard cell zeaxanthin has a regulatory role in the light response of stomata. Zeaxanthin also appears to mediate light-CO2 interactions in guard cells.
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