8-nitro-cGMP acts as a guard cell signaling molecule in stomata


Nitrated cyclic GMP modulates guard cell signaling in Arabidopsis 

by Joudoi T., Shichiri Y., Kamizono N., Akaike T., Sawa T., Yoshitake J., Yamada N., Iwai S. (2013)

 in The Plant Cell 25558571. – doi: http://dx.doi.org/10.1105/tpc.112.105049 – 

Abstract/FREE Full Text


Nitric oxide (NO) is a ubiquitous signaling molecule involved in diverse physiological processes, including plant senescence and stomatal closure.

The NO and cyclic GMP (cGMP) cascade is the main NO signaling pathway in animals, but whether this pathway operates in plant cells, and the mechanisms of its action, remain unclear.

Here, we assessed the possibility that the nitrated cGMP derivative 8-nitro-cGMP functions in guard cell signaling. Mass spectrometry and immunocytochemical analyses showed that abscisic acid and NO induced the synthesis of 8-nitro-cGMP in guard cells in the presence of reactive oxygen species.

8-Nitro-cGMP triggered stomatal closure, but 8-bromoguanosine 3′,5′-cyclic monophosphate (8-bromo-cGMP), a membrane-permeating analog of cGMP, did not. However, in the dark, 8-bromo-cGMP induced stomatal opening but 8-nitro-cGMP did not.

Thus, cGMP and its nitrated derivative play different roles in the signaling pathways that lead to stomatal opening and closure. Moreover, inhibitor and genetic studies showed that calcium, cyclic adenosine-5′-diphosphate-ribose, and SLOW ANION CHANNEL1 act downstream of 8-nitro-cGMP.

This study therefore demonstrates that 8-nitro-cGMP acts as a guard cell signaling molecule and that a NO/8-nitro-cGMP signaling cascade operates in guard cells.


AtCLCc, stomatal movements and salt tolerance


The Arabidopsis vacuolar anion transporter, AtCLCc, is involved in the regulation of stomatal movements and contributes to salt tolerance.

by Jossier M., Kroniewicz L., Dalmas F., Le Thiec D., Ephritikhine G., Thomine S., Barbier-Brygoo H., Vavasseur A., Filleur S., Leonhardt N. (2010)

in Plant J. 64563576(2010). – doi: 10.1111/j.1365-313X.2010.04352.x. –



In plant cells, anion channels and transporters are essential for key functions such as nutrition, resistance to biotic or abiotic stresses, and ion homeostasis. In Arabidopsis, members of the chloride channel (CLC) family located in intracellular organelles have been shown to be required for nitrate homeostasis or pH adjustment, and previous results indicated that AtCLCc is involved in nitrate accumulation.

We investigated new physiological functions of this CLC member in Arabidopsis. Here we report that AtCLCc is strongly expressed in guard cells and pollen and more weakly in roots.

Use of an AtCLCc:GFP fusion revealed localization to the tonoplast. Disruption of the AtCLCc gene by a T-DNA insertion in four independent lines affected physiological responses that are directly related to the movement of chloride across the tonoplast membrane.

Opening of clcc stomata was reduced in response to light, and ABA treatment failed to induce their closure, whereas application of KNO₃ but not KCl restored stomatal opening.

clcc mutant plants were hypersensitive to NaCl treatment when grown on soil, and to NaCl and KCl in vitro, confirming the chloride dependence of the phenotype. These phenotypes were associated with modifications of chloride content in both guard cells and roots.

These data demonstrate that AtCLCc is essential for stomatal movement and salt tolerance by regulating chloride homeostasis.

ABA and stomatal behaviour


Suppression of stomatal opening in leaves treated with abscisic acid.

by Jones R. J.Mansfield T. A. (1970)

in Journal of Experimental Botany 21714719. – doi: 10.1093/jxb/21.3.714 – 

CrossRef |CAS |


Small doses of abscisic acid (approximately 0.02 μg cm-2 of leaf) applied to the leaf surface as a 10-4 M solution caused marked stomatal closure in Xanthium pennsylvanicum, and the effect persisted for up to 9 days after application.

Similar effects were found when 10-4 M abscisic acid was supplied to detached tobacco leaves via their petioles.

CO2-free air did not cause a reversal of the closure, and it was therefore concluded that the effect was not due simply to an increase in the intercellular CO2concentration; a more direct effect on the stomatal apparatus is suggested.

It is considered that abscisic acid could play an endogenous role in the control of stomatal aperture, and that this, and/or related substances, might be more useful as ‘anti-transpirants’ than the phytotoxic substances currently employed for this purpose.

Thermography and stomatal conductance


Use of thermography for quantitative studies of spatial and temporal variation of stomatal conductance over leaf surfaces.

by Jones H. G. (1999)

in Plant Cell Environ 22: 1043–1055. – DOI: 10.1046/j.1365-3040.1999.00468.x – 



This paper describes a new approach to the calibration of thermal infrared measurements of leaf temperature for the estimation of stomatal conductance and illustrates its application to thermal imaging of plant leaves.

The approach is based on a simple reformulation of the leaf energy balance equation that makes use of temperature measurements on reference surfaces of known conductance to water vapour.

The use of reference surfaces is an alternative to the accurate measurement of all components of the leaf energy balance and is of potentially wide application in studies of stomatal behaviour.

The resolution of the technique when applied to thermal images is evaluated and some results of using the approach in the laboratory for the study of stomatal behaviour in leaves of Phaseolus vulgaris L. are presented.

Conductances calculated from infrared measurements were well correlated with estimates obtained using a diffusion porometer.

Stomatal and non-stomatal limitations to photosynthesis


Partitioning stomatal and non-stomatal limitations to photosynthesis.

by Jones H. G. (1985)

in Plant, Cell and Environment 895104. – DOI: 10.1111/j.1365-3040.1985.tb01227.x

Wiley Online Library |


Plant scientists concerned both with crop improvement and with understanding the control mechanisms of complex processes such as photosynthesis need to identify those processes that are most important in restricting the overall rate and to quantify the relative importance of different components. The techniques that have been used for quantifying the relative importance of component processes in limiting net assimilation rate are reviewed and related to a fundamental definition based on sensitivity analysis. It is concluded that many methods currently in use, including standard resistance analysis, frequently give very misleading answers.

In addition, possible methods for apportioning the contributions of different component processes to observed changes in net photosynthetic rate (for example after stress) are also reviewed and compared against a fundamental approach based on sensitivity analysis.

Unfortunately, the detailed time course of changes in mesophyll and stomatal properties that is required for application of the basic sensitivity analysis is seldom likely to be available, so that it is usually necessary to adopt an approximate method. The standard approximation that is recommended for calculating the contributions of different component processes to a change in assimilation rate, involves measurements at the initial and final states only. The various methods discussed in this paper are compared using published photosynthetic data for a range of species.

Regulation of stomatal apertures by MPK9 and MPK12 contributes to the first line of defense against pathogens.


Two Arabidopsis guard cell-preferential MAPK genes, MPK9 and MPK12, function in biotic stress response.

by Jammes F.,002skz2nmolsmh4

Yang X.,MJB_4592

Xiao S.,Shunyuan_Xiao2

Kwak J. M.MyPhoto1_93X150


  • a University of Maryland; College Park, MD, USA
  • b Department of Cell Biology and Molecular Genetics
  • c Institute for Bioscience and Biotechnology Research
  • d Institute for Bioscience and Biotechnology Research; Department of Plant Molecular Systems Biotechnology and Crop Biotech Institute; Kyung Hee University; Yongin, Korea


in Plant Signal. Behav. 6, 1875–1877. doi: 10.4161/psb.6.11.17933 –

PubMed Abstract | CrossRef Full Text | Google Scholar


Abscisic acid (ABA) plays a major role in plant development and adaptation to severe environmental conditions. ABA evokes cellular events to regulate stomatal apertures and thus contributes to the plant’s ability to respond to abiotic stresses. Reactive oxygen species (ROS) are produced in response to ABA and mediate ABA-induced stomatal closure.
We have shown that two MAP kinases, MPK9 and MPK12, are highly and preferentially expressed in guard cells and function as positive regulators of ROS-mediated ABA signaling in guard cells.
Cell biological and electrophysiological analyses demonstrated that MPK9 and MPK12 act downstream of ROS and cytosolic Ca2+ and upstream of anion channels in the guard cell ABA signaling cascade.
Plant pathogens use stomata as the primary gateway to enter into their hosts, and previous studies have indicated crosstalk between ABA and defense signaling. Here we show that mpk9-1/12-1double mutants are highly susceptible to Pseudomonas syringae DC3000 compared to WT plants.
These results suggest that the regulation of stomatal apertures by MPK9 and MPK12 contributes to the first line of defense against pathogens.


MPK9 and MPK12 function downstream of ROS to regulate guard cell ABA signaling positively.


MAP kinases MPK9 and MPK12 are preferentially expressed in guard cells and positively regulate ROS-mediated ABA signaling.

by Jammes F., Song C., Shin D., Munemasa S., Takeda K., Gu D., Choa D., Lee S., Giordo R.,  Sritubtim S., Leonhardt N., Ellis B. E., Murata Y., Kwak J. M. (2009)

  1. Fabien Jammesa,1,
  2. Charlotte Songa,1,2,
  3. Dongjin Shina,1,3,
  4. Shintaro Munemasab,
  5. Kouji Takedaa,
  6. Dan Gua,
  7. Daeshik Choa,
  8. Sangmee Leea,
  9. Roberta Giordoa,c,
  10. Somrudee Sritubtimd,4,
  11. Nathalie Leonhardte,
  12. Brian E. Ellisd,
  13. Yoshiyuki Muratab and
  14. June M. Kwaka,5

in Proc. Natl. Acad. Sci. U.S.A. 106, 20520–20525. doi: 10.1073/pnas.0907205106 –

PubMed Abstract | CrossRef Full Text | Google Scholar


Reactive oxygen species (ROS) mediate abscisic acid (ABA) signaling in guard cells. To dissect guard cell ABA-ROS signaling genetically, a cell type-specific functional genomics approach was used to identify 2 MAPK genes, MPK9 and MPK12, which are preferentially and highly expressed in guard cells.

To provide genetic evidence for their function, Arabidopsis single and double TILLING mutants that carry deleterious point mutations in these genes were isolated. RNAi-based gene-silencing plant lines, in which both genes are silenced simultaneously, were generated also. Mutants carrying a mutation in only 1 of these genes did not show any altered phenotype, indicating functional redundancy in these genes.

ABA-induced stomatal closure was strongly impaired in 2 independent RNAi lines in which both MPK9 and MPK12 transcripts were significantly silenced. Consistent with this result, mpk9-1/12-1 double mutants showed an enhanced transpirational water loss and ABA- and H2O2-insensitive stomatal response.

Furthermore, ABA and calcium failed to activate anion channels in guard cells of mpk9-1/12-1, indicating that these 2 MPKs act upstream of anion channels in guard cell ABA signaling.

An MPK12-YFP fusion construct rescued the ABA-insensitive stomatal response phenotype of mpk9-1/12-1, demonstrating that the phenotype was caused by the mutations. The MPK12 protein is localized in the cytosol and the nucleus, and ABA and H2O2 treatments enhance the protein kinase activity of MPK12.

Together, these results provide genetic evidence that MPK9 and MPK12 function downstream of ROS to regulate guard cell ABA signaling positively.