Scientists Investigate the Role of PEPCK in Malate Metabolism During Stomatal Closure

Malate is one of the important solutes for maintaining turgor pressure during stomatal opening. This solute  has been known to come from the guard cells, however, it is not yet clear if it is also metabolized. University of York scientist Steven Penfield and colleagues provided evidence than an enzyme (phosphoenolpyruvate carboxykinase or PEPCK) involved in malate metabolism and glucose formation is needed for complete closure of the stomata under dark conditions.

Analysis of PCK1 gene showed that PEPCK is expressed in guard cells and trichomes of the leaf. Mutant plants with altered gene exhibited reduced tolerance to drought as well as increased stomatal conductance and wider stomatal apertures compared with the wild type. When exposed to light and dark conditions, the mutant plants showed increased stomatal conductance and less sensitivity of the stomata to darkness, which imply that the stomata becomes stacked in the open position. Based on these findings, the researchers concluded that malate metabolism is important in dark-induced stomatal closure where PEPCK plays a significant role.

Read the abstract at http://onlinelibrary.wiley.com/doi/10.1111/j.1365-313X.2011.04822.x/abstract.