Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO2‐ and ABA‐induced stomatal closing. (22nd July 2015)

• Record Type: Journal Article
• Authors: Azoulay‐Shemer, Tamar; Palomares, Axxell; Bagheri, Andisheh; Israelsson‐Nordstrom, Maria; Engineer, Cawas B.; Bargmann, Bastiaan O. R.; Stephan, Aaron B.; Schroeder, Julian I.
• Is Part Of: Plant journal. Volume 83:Number 4(2015:Aug.)
• Page Start: 567
• Page End: 581
• Publication Date: 2015-07-22
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12916
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12916-abs-0001"> <title>Summary</title> <p>Stomata mediate gas exchange between the inter‐cellular spaces of leaves and the atmosphere. CO<sub>2</sub> levels in leaves (<italic>Ci</italic>) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO<sub>2</sub>]. [CO<sub>2</sub>] in leaves mediates stomatal movements. The role of guard cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll‐deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard cell specific enhancer trap line. Our data show that more than 90% of guard cells were chlorophyll‐deficient. Interestingly, approximately 45% of stomata had an unusual, previously not‐described, morphology of thin‐shaped chlorophyll‐less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole‐leaf photosynthetic parameters (PSII, qP, qN, <italic> F</italic><sub>V</sub>′/<italic>F</italic><sub>M′</sub>) were comparable with wild‐type plants. Time‐resolved intact leaf gas‐exchange analyses showed a reduction in stomatal conductance and CO<sub>2</sub>‐assimilation rates of the transgenic plants. Normalization of CO<sub>2</sub> responses showed that stomata of transgenic plants respond to [CO<sub>2</sub>] shifts. Detailed stomatal aperture measurements of normal kidney‐shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO<sub>2</sub>] elevation and abscisic acid (ABA), while thin‐shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO<sub>2</sub>] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard cell CO<sub>2</sub> and ABA signal transduction are not directly modulated by guard cell photosynthesis/electron transport. Moreover, the finding that chlorophyll‐less stomata cause a 'deflated' thin‐shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard cell turgor production.</p> </abstract>