Phospholipase A2β mediates light-induced stomatal opening in Arabidopsis

Phospholipase A2 (PLA2) catalyses the hydrolysis of phospholipids into lysophospholipids and free fatty acids. Physiological studies have indicated that PLA2 is involved in stomatal movement. However, genetic evidence of a role of PLA2 in guard cell signalling has not yet been reported. To identify PLA2 gene(s) that is (are) involved in light-induced stomatal opening, stomatal movement was examined in Arabidopsis thaliana plants in which the expression of PLA2 isoforms was reduced or knocked-out. Light-induced stomatal opening in PLA2α knockout plants did not differ from wild-type plants. Plants in which PLA2β was silenced by RNA interference exhibited delayed light-induced stomatal opening, and this phenotype was reversed by exogenous lysophospholipids, which are products of PLA2. Stomatal opening in transgenic plants that over-expressed PLA2β was faster than wild-type plants. The expression of PLA2β was localized to the endoplasmic reticulum of guard cells, and increased in response to light in the mature leaf. Aristolochic acid, which inhibits light-induced stomatal opening, inhibited the activity of purified PLA2β. Collectively, these results provide evidence that PLA2β is involved in light-induced stomatal opening in Arabidopsis

A receptor-like kinase mutant with absent endodermal diffusion barrier displays selective nutrient homeostasis defects

We thank the Genomic Technologies Facility (GTF) and the Central Imaging Facility (CIF) of the University of Lausanne for expert technical support. We thank Valérie Dénervaud Tendon, Guillaume Germion, Deborah Mühlemann, and Kayo Konishi for technical assistance and John Danku and Véronique Vacchina for ICP-MS analysis. This work was funded by grants from the Swiss National Science Foundation (SNSF), the European Research Council (ERC) to NG and a Human Frontiers Science Program (HFSP) grant to JT and NG. GL and CM were supported by the Agropolis foundation (Rhizopolis) and the Agence Nationale de la Recherche (HydroRoot; ANR-11-BSV6-018). MB was supported by a EMBO long-term postdoctoral fellowship, JEMV by a Marie Curie IEF fellowship and TK by the Japan Society for the Promotion of Sciences (JSPS).Peer reviewedPublisher PD

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

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. © 2016 Institute for Basic Science / DGIST1

Roles of phosphoinositides in regulation of stomatal movements

Guard cells sense various environmental and internal stimuli and, in response, modulate the stomatal aperture to a size optimal for growth and adaptation. Among the many factors involved in the fine regulation of stomata, we have focused our studies on the role of phosphoinositides. Our recent study published in the Plant Journal (52:803–16) provides evidence for an important role for phosphatidylinositol 4,5-bis-phosphate (PtdIns(4,5)P2) in inducing stomatal opening. Light induces translocation of a PtdIns(4,5)P2-binding protein from the cytosol to the plasma membrane and treatments that increase the intracellular PtdIns(4,5)P2 level induce stomatal opening in the absence of light irradiation. Inhibition of anion channel activity, a negative regulator for stomatal opening, was suggested as a mechanism of PtdIns(4,5)P2-induced stomatal opening. We also reported that phosphatidylinositol 3-phosphate (PtdIns(3)P) and phosphatidylinositol 4-phosphate (PtdIns(4)P) regulate actin dynamics in guard cells. The effects of the phosphoinositides were specific, and were not induced by other lipids with similar structures. The roles of different interacting partners are likely to be important for these lipids to produce specific changes in guard cell activity

Cellular coordination controlling organ separation and surface integrity in plants

Plants are unable to relocate themselves to a more favorable location and thus have to deal with developmental programs and environmental cues wherever they happen to be. It is yet largely unknown how plant cells coordinate cellular activities and architectures to accomplish developmental processes and respond to environmental changes. By identifying and establishing a new cellular model system, we have discovered that two neighboring cell types in the abscission zone (AZ) of Arabidopsis flowers coordinate their activities to ensure a precise "cut" through a highly restricted area of plant tissue to bring about organ separation. From this perspective, we further discuss the essence of cellular coordination in AZ, the key molecules controlling the organ separation, and relevant implications. ⓒ 2018 by the The Korean Society for Biochemistry and Molecular Biolog

MAPK Cascades in Guard Cell Signal Transduction

Guard cells form stomata on the epidermis and continuously respond to endogenous and environmental stimuli to fine-tune the gas exchange and transpirational water loss, processes which involve mitogen-activated protein kinase (MAPK) cascades. MAPKs form three-tiered kinase cascades with MAPK kinases and MAPK kinase kinases, by which signals are transduced to the target proteins. MAPK cascade genes are highly conserved in all eukaryotes, and they play crucial roles in myriad developmental and physiological processes. MAPK cascades function during biotic and abiotic stress responses by linking extracellular signals received by receptors to cytosolic events and gene expression. In this review, we highlight recent findings and insights into MAPK-mediated guard cell signaling, including the specificity of MAPK cascades and the remaining questions. Copyright © 2016 Lee, Kim, Kim and Kwak. This is an open-access article distributed under the terms of the Creative Commons Attribution License(CCBY).120231sciescopu

Insomnia and Parental Overprotection are Associated with Academic Stress among Medical Students

Background and Objective The purpose of this study was to explore particular aspects of the mental health status of medical students and to identify relationships among them. Methods All 191 medical students from University of Ulsan College of Medicine were included in this study. Psychological parameters were measured with the Medical Stress Scale (MSS), Insomnia Severity Index, Korean-Parental Overprotection Scale, Patient Health Questionnaire-9 and Academic Motivation Scale. Results Stressed students (MSS ≥ 28) had significantly higher scores on insomnia severity (5.8 ± 4.5 vs 4.4 ± 3.0, p < 0.05), depression (5.7 ± 4.5 vs 2.6 ± 2.4, p < 0.01), and amotivation (9.3 ± 3.3 vs 6.9 ± 2.2, p < 0.01) and lower scores of intrinsic motivation (3.5 ± 7.1 vs. 41.7 ± 7.2, p < 0.01) compared to non-stressed students (MSS < 28). Significant correlations were noted between several factors and Medical Stress Scores. Specifically, insomnia, depression, amotivation and maternal ‘face culture’ of parental overprotection, had independent and significant influences on academic stress reported by medical students (R2 = 0.39, p < 0.01). Conclusions Our findings revealed insomnia, depression, academic motivation and parental overprotection are relevant factors influencing stress in medical students. Current results provide insights for stress management including the importance of parenting intervention