AUTHOR=Liu Xuan-shan , Liang Chao-chao , Hou Shu-guo , Wang Xin , Chen Dong-hua , Shen Jian-lin , Zhang Wei , Wang Mei 

TITLE=The LRR-RLK Protein HSL3 Regulates Stomatal Closure and the Drought Stress Response by Modulating Hydrogen Peroxide Homeostasis

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.548034

DOI=10.3389/fpls.2020.548034

ISSN=1664-462X

ABSTRACT=<p>Guard cells shrink in response to drought stress and abscisic acid (ABA) signaling, thereby reducing stomatal aperture. Hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) is an important signaling molecule acting to induce stomatal closure. As yet, the molecular basis of control over the level of H<sub>2</sub>O<sub>2</sub> in the guard cells remains largely unknown. Here, the leucine-rich repeat (LRR)—receptor-like kinase (RLK) protein HSL3 has been shown to have the ability to negatively regulate stomatal closure by modulating the level of H<sub>2</sub>O<sub>2</sub> in the guard cells. <italic>HSL3</italic> was markedly up-regulated by treating plants with either ABA or H<sub>2</sub>O<sub>2</sub>, as well as by dehydration. In the loss-of-function <italic>hsl3</italic> mutant, both stomatal closure and the activation of anion currents proved to be hypersensitive to ABA treatment, and the mutant was more tolerant than the wild type to moisture deficit; the overexpression of <italic>HSL3</italic> had the opposite effect. In the <italic>hsl3</italic> mutant, the transcription of NADPH oxidase gene <italic>RbohF</italic> involved in H<sub>2</sub>O<sub>2</sub> production showed marked up-regulation, as well as the level of catalase activity was weakly inducible by ABA, allowing H<sub>2</sub>O<sub>2</sub> to accumulate in the guard cells. HSL3 was concluded to participate in the regulation of the response to moisture deficit through ABA-induced stomatal closure triggered by the accumulation of H<sub>2</sub>O<sub>2</sub> in the guard cells.</p>