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Plant J. 2015 Aug;83(4):567-81. doi: 10.1111/tpj.12916. Epub 2015 Jul 22.

Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO2 - and ABA-induced stomatal closing.

Author information

1
Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla, CA, 92093-0116, USA.
2
Umeå Plant Science Centr, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, S901 83, Umeå, Sweden.
3
Biology Department, Center for Genomics and Systems Biology, New York University, New York, NY, 10003, USA.

Abstract

Stomata mediate gas exchange between the inter-cellular spaces of leaves and the atmosphere. CO2 levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO2 ]. [CO2 ] 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, FV '/FM' ) were comparable with wild-type plants. Time-resolved intact leaf gas-exchange analyses showed a reduction in stomatal conductance and CO2 -assimilation rates of the transgenic plants. Normalization of CO2 responses showed that stomata of transgenic plants respond to [CO2 ] shifts. Detailed stomatal aperture measurements of normal kidney-shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO2 ] elevation and abscisic acid (ABA), while thin-shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO2 ] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard cell CO2 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.

KEYWORDS:

Arabidopsis thaliana; CO 2; abscisic acid; chlorophyll; chlorophyllase; guard cell; photosynthesis; stomata; turgor

PMID:
26096271
PMCID:
PMC4532624
DOI:
10.1111/tpj.12916
[Indexed for MEDLINE]
Free PMC Article

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