Stress-Related Changes in the Expression and Activity of Plant Carbonic Anhydrases

摘要

The data on stress-related changes in the expression and activity of plant carbonic anhydrases (CAs) suggest that they are generally upregulated at moderate stress severity. This indicates probable involvement of CAs in adaptation to drought, high salinity, heat, high light, C-i deficit, and excess bicarbonate. The changes in CA levels under cold stress are less studied and generally represented by the downregulation of CAs excepting beta CA2. Excess Cd2+ and deficit of Zn2+ specifically reduce CA activity and reduce its synthesis. Probable roles of beta CAs in stress adaptation include stomatal closure, ROS scavenging and partial compensation for decreased mesophyll CO2 conductance. beta CAs play contrasting roles in pathogen responses, interacting with phytohormone signaling networks. Their role can be either negative or positive, probably depending on the host-pathogen system, pathogen initial titer, and levels of center dot NO and ROS. It is still not clear why CAs are suppressed under severe stress levels. It should be noted, that the role of beta CAs in the facilitation of CO2 diffusion and their involvement in redox signaling or ROS detoxication are potentially antagonistic, as they are inactivated by oxidation or nitrosylation. Interestingly, some chloroplastic beta CAs may be relocated to the cytoplasm under stress conditions, but the physiological meaning of this effect remains to be studied.