Abstract
BackgroundStomata are micropores surrounded by pairs of guard cells, and their opening is finely controlled to balance water vapor loss as transpiration and CO2 absorption for photosynthesis. The regulatory signaling network for stomatal movement is complicated, and increasing numbers of new genes have been shown to be involved in this process. Our previous study indicated that a member of the plant putative mitochondrial pyruvate carrier (MPC) family, NRGA1, is a negative regulator of guard cell abscisic acid (ABA) signaling. In this study, we identified novel physiological roles of pyruvate and MPC1, another member of the MPC family, in the regulation of stomatal closure in Arabidopsis.ResultsLoss-of-function mutants of MPC1 (mpc1) were hypersensitive to ABA-induced stomatal closure and ABA-activated guard cell slow-type anion currents, and showed a reduced rate of water loss upon drought treatment compared with wild-type plants. In contrast, plants overexpressing MPC1 showed a hyposensitive ABA response and increased sensitivity to drought stress. In addition, mpc1 mutants accumulated more pyruvate after drought or ABA treatment. The increased pyruvate content also induced stomatal closure and activated the slow-type anion channels of guard cells, and this process was dependent on the function of RbohD/F NADPH oxidases and reactive oxygen species concentrations in guard cells.ConclusionsOur findings revealed the essential roles of MPC1 and pyruvate in stomatal movement and plant drought resistance.
Highlights
Stomata are micropores surrounded by pairs of guard cells, and their opening is finely controlled to balance water vapor loss as transpiration and CO2 absorption for photosynthesis
Expression pattern of Arabidopsis thaliana mitochondrial pyruvate carrier 1 (AtMPC1) in A. thaliana Previously, the pyruvate carrier function of AtMPC1 in the yeast mutant mpc1Δ was confirmed by complementation analysis [18], and co-localization of GFP-tagged MPC1 and RFP-tagged NRGA1 indicated that AtMPC1 was deposited in the mitochondria, co-localizing with NRGA1 [27]
GUS staining indicated that AtMPC1 was ubiquitously expressed in the leaf, root, silique, and flowers, with a high expression level in epidermal guard cells (Fig. 1), which suggests important functions of AtMPC1 in different tissues, especially in guard cells of the epidermis
Summary
Stomata are micropores surrounded by pairs of guard cells, and their opening is finely controlled to balance water vapor loss as transpiration and CO2 absorption for photosynthesis. Our previous study indicated that a member of the plant putative mitochondrial pyruvate carrier (MPC) family, NRGA1, is a negative regulator of guard cell abscisic acid (ABA) signaling. Among the diverse pathways that plants have evolved to either tolerate or adapt to this stress, the control of stomatal aperture by regulating turgor in the pair of guard cells surrounding each stoma is perhaps the most important [2, 3]. The cytosol reactive oxygen species (ROS) is elevated in response to ABA accumulation, and is involved in ABA-regulated transmembrane ion trafficking of guard cells to close stomata [12,13,14,15], and the NADPH oxidases, e.g. RbohD and RbohF, are needed in the ABA activated ROS production [16]. With regard to the complex signaling networks influencing stomatal aperture, many novel functional genes, proteins, and factors were found to be involved in the molecular mechanisms of ABA signaling and stomatal movement [17]
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