The function of ABA transporters during low humidity-induced stomatal closure in Arabidopsis thaliana.
Plants are important for our nature and for all living things. These organisms can produce food, energy and several natural products from carbon dioxide and solar energy. Plants take up CO2 from the air in exchange for water via small pores called stomata on the leaf surface. These stomata are formed by pairs of cells, called guard cells. As plants are sessile organisms, they cannot move and need to adapt their physiology to the imposed environmental conditions. Drought is one of the major problems caused by climate change and guard cell physiology plays an important role in regulating stomatal apertures and the plant water content. For stomatal aperture regulation under limiting water conditions, the plant hormone abscisic acid (ABA) plays a major role. To understand guard cell physiology and the role of ABA in the plant response to low air humidity, defined as the Vapor Pressure Deficit (VPD) between plants and the atmosphere, we performed gas exchange analyses using Arabidopsis thaliana wild type plants and mutants in which ABA transporter genes were disrupted. Among the tested mutants, we observed a slower VPD response in a mutant in which the ABCG22 gene was disrupted. However, we did not observe clearly altered high VPD responses of abcg25, abcg31, abcg40, npf4.6 and npf5.2 ABA transporter mutants. This may be due to a high functional overlap between several ABA transporter genes. We also performed gene expression analyses of ABA transporter genes using the Genevestigator tool. This allowed us to propose the testing of additional ABA transporter genes that might be relevant for the high VPD response in Arabidopsis.
ABA, ABA transport, guard cells, stomatal closure, stomatal conductance, VPD response