L-Met Activates Arabidopsis GLR Ca2+ Channels Upstream of ROS Production and Regulates Stomatal Movement

• Published in: Cell reports (Cambridge) 2016-12, Vol.17 (10), p.2553-2561
• Main Authors: Kong, Dongdong, Hu, Heng-Cheng, Okuma, Eiji, Lee, Yuree, Lee, Hui Sun, Munemasa, Shintaro, Cho, Daeshik, Ju, Chuanli, Pedoeim, Leah, Rodriguez, Barbara, Wang, Juan, Im, Wonpil, Murata, Yoshiyuki, Pei, Zhen-Ming, Kwak, June M.
• Format: Article
• Language: English
• Subjects: Ca2+ channel; Ca2+ deficiency; glutamate receptor homologs; guard cell; L-methionine; reactive oxygen species; stomatal movement
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2016.11.015

Plant glutamate receptor homologs (GLRs) have long been proposed to function as ligand-gated Ca2+ channels, but no in planta evidence has been provided. Here, we present genetic evidence that Arabidopsis GLR3.1 and GLR3.5 form Ca2+ channels activated by L-methionine (L-Met) at physiological concentrations and regulate stomatal apertures and plant growth. The glr3.1/3.5 mutations resulted in a lower cytosolic Ca2+ level, defective Ca2+-induced stomatal closure, and Ca2+-deficient growth disorder, all of which involved L-Met. Patch-clamp analyses of guard cells showed that GLR3.1/3.5 Ca2+ channels are activated specifically by L-Met, with the activation abolished in glr3.1/3.5. Moreover, GLR3.1/3.5 Ca2+ channels are distinct from previously characterized ROS-activated Ca2+ channels and act upstream of ROS, providing Ca2+ transients necessary for the activation of NADPH oxidases. Our data indicate that GLR3.1/3.5 constitute L-Met-activated Ca2+ channels responsible for maintaining basal [Ca2+]cyt, play a pivotal role in plant growth, and act upstream of ROS, thereby regulating stomatal aperture. [Display omitted] •GLR3.1 and GLR3.5 form guard cell Ca2+ channels specifically activated by L-Met•GLR3.1/3.5 Ca2+ channels contribute to maintenance of basal cytosolic Ca2+ levels•GLR3.1/3.5 Ca2+ channels act upstream of reactive oxygen species•GLR3.1/3.5 Ca2+ channels play a role in plant growth and stomatal movement Kong et al. show that Arabidopsis glutamate receptor homologs GLR3.1 and GLR3.5 form L-methionine-activated Ca2+ channels. The GLR3.1/3.5 Ca2+ channels are distinct from ROS-activated Ca2+ channels and play a role in maintaining basal cytosolic Ca2+ levels, thereby regulating stomatal movements and plant growth.