HPCA1 and HSL3: two plasma membrane proteins that probably cooperate to modulate H2O2 signalling under drought conditions

HO is an essential component of reactive oxygen species (ROS) metabolism and an obligatory side-product of aerobic respiration among plant cells. It is needed for plant growth, development, and stress management along with signalling properties. HO is intricately involved in the stomatal closure during drought stress in conjunction with abscisic acid (ABA), calcium ions (Ca), nitric oxide (NO) and hydrogen sulfide (HS) among others rendering an enhanced plant tolerance. Protein kinases are part of the diverse signalling cascades. Identification of such unique cell surface receptors and proteins for ligand perception and relaying of signals enables us with a better understanding and developing strategies and genetic lines that may combat climatic variations. Here, it points out two recent findings in Arabidopsis: (i) the extracellular HO sensor HPCA1 which is an LRR (leucine-rich-repeat) receptor kinase; and, (ii) the leucine-rich repeat (LRR)-receptor-like kinase (RLK) protein HSL3 which both probably cooperate to modulate HO as a signal in response to drought stress. Therefore, it could be hypothesized that this HO signaling mechanism could function in other types of environmental stresses.Dr. Vijay Pratap Singh is thankful to the Science and Engineering Research Board, New Delhi (EMR/2017/000518) for providing financial assistance to carry out this work. FJC research is supported by a European Regional Development Fund cofinanced grant from the Spanish Ministry of Economy and Competitiveness (PID2019-103924GB-I00), the Plan Andaluz de Investigación, Desarrollo e Innovación (PAIDI 2020) (P18-FR-1359) and Junta de Andalucía (group BIO192), Spain