Sensing the environment: key roles of membrane-localized kinases in plant perception and response to abiotic stress.

Adverse environmental conditions have negative effects on plant growth and development. Receptor proteins on the plasma membrane sense various environmental stimuli and transduce them to downstream intra- and intercellular signalling networks. Receptor-like kinases (RLKs) play important roles in perceiving the extracellular ligands and activating the downstream pathway via phosphorylation of intracellular serine/threonine kinase domains. The Arabidopsis genome possesses >600 RLK-encoding genes, some of which are implicated in the perception of environmental signals during the life cycle of the sessile plants. Histidine kinases are also membrane-localized kinases and perceive osmotic stress and plant hormones. In this review, we focus on the RLKs and histidine kinases that play a role in plant response to abiotic stresses. We summarize our recent understanding of their specific roles in stress responses and absicisic acid (ABA) regulation. Elucidation of the functions of these kinases in the osmotic stress response will provide a better understanding of stress-sensing mechanisms in plants and help to identify potential candidate genes for genetic engineering of improved stress-tolerant crops.