Proteins identified in guard cells are localized in all known subcellular localizations. Numbers in parentheses are the numbers of proteins in each cellular compartment identified in the Arabidopsis guard cell proteome of Zhao et al. (2008, 2010). PHOT1 (At3g45780, blue light photoreceptor), PHOT2 (At5g58140, blue light photoreceptor), CAS (At5g23060, calcium-sensing receptor), CHX20 (At3g53720, cation/H+ exchanger 20), NIA2 (At1g37130, nitrogen reductase 2), CPK3 (At4g23650, calcium-dependent protein kinase 3), OST2 (At2g18960, open stomata 2), KAT2 (At4g18290, potassium channel), and PLDα1 (At3g15730, phospholipase D alpha 1) are proteins identified in that study (Zhao et al., 2008, 2010) which are known to be involved in light/ABA signalling in guard cells according to previous studies. TGG1 (At5g26000, myrosinase) was identified to be the most abundant protein in guard cells by mass spectrometry methods (Zhao et al., 2008). OST2 is a H+ ATPase, KAT2 is a K+channel, and PIP1B is an aquaporin.
The glycolytic enzyme, phosphoglycerate mutase, has critical roles in stomatal movement, vegetative growth, and pollen production in Arabidopsis thaliana.
by Zhao Z., Assmann S. M. (2011)
Biology Department, Penn State University, University Park, Pennsylvania 16802
Zhixin Zhao, Sarah M. Assmann
Biology Department, 208 Mueller Laboratory, Penn State University, University Park, PA 16802, USA.
in J Exp Bot. 2011 Oct;62(14):5179-89. doi: 10.1093/jxb/err223. Epub 2011 Aug 3. – PMID: 21813794 –
ipgam1 ipgam2 double mutants have vegetative and reproductive phenotypes. (A) Double mutant plants are dramatically shorter than Col plants. (B) Double mutant rosette leaf areas are dramatically reduced compared with Col plants. For A and B, n=10. Data are mean ±SE. (D) Leaves from double ipgam mutants exhibit a pale, slightly reticulate phenotype. (C) No visible pollen grains were found in double mutant anthers. Col and double 1 plants are shown. The same phenotype was present in double 2 (data not shown).
Stomatal movements require massive changes in guard cell osmotic content, and both stomatal opening and stomatal closure have been shown to be energy-requiring processes.
A possible role for glycolysis in contributing to the energetic, reducing requirements, or signalling processes regulating stomatal movements has not been investigated previously.
Glycolysis, oxidization of glucose to pyruvate, is a central metabolic pathway and yields a net gain of 2 ATP and 2 NADH. 2,3-biphosphoglycerate-independent phosphoglycerate mutase (iPGAM) is a key enzymatic activity in glycolysis and catalyses the reversible interconversion of 3-phosphoglycerate to 2-phosphoglycerate.
To investigate functions of iPGAMs and glycolysis in stomatal function and plant growth, Arabidopsis insertional mutants in At1g09780 and At3g08590, both of which have been annotated as iPGAMs on the basis of sequence homology, were identified and characterized.
While single mutants were indistinguishable from the wild type in all plant phenotypes assayed, double mutants had no detectable iPGAM activity and showed defects in blue light-, abscisic acid-, and low CO(2)-regulated stomatal movements.
Vegetative plant growth was severely impaired in the double mutants and pollen was not produced. The data demonstrate that iPGAMs and glycolytic activity are critical for guard cell function and fertility in Arabidopsis.