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Plant growth and development and interactions with the environment are regulated by phytohormones and other signaling molecules. During their evolution, plants have developed strategies for efficient signal perception and for the activation of signal transduction cascades to maintain proper growth and development, in particular under adverse environmental conditions. Abscisic acid (ABA) is one of the phytohormones known to regulate plant developmental events and tolerance to environmental stresses. The role of ABA is mediated by both its accumulated level, which is regulated by its biosynthesis and catabolism, and signaling, all of which are influenced by complex regulatory mechanisms. Under stress conditions, plants employ enzymatic and non-enzymatic antioxidant strategies to scavenge excess reactive oxygen species (ROS) and mitigate the negative effects of oxidative stress. Glutathione (GSH) is one of the main antioxidant molecules playing a critical role in plant survival under stress conditions through the detoxification of excess ROS, maintaining cellular redox homeostasis and regulating protein functions. GSH has recently emerged as an important signaling molecule regulating ABA signal transduction and associated developmental events, and response to stressors. This review highlights the current knowledge on the interplay between ABA and GSH in regulating seed dormancy, germination, stomatal closure and tolerance to drought. [ABSTRACT FROM AUTHOR]

Abstract Salinity stress adversely affects plant growth and development. Calcineurin B-like proteins (CBLs) are a family of plant calcium sensors that relay signals by interacting with a family of CBL-interacting protein kinases (CIPKs). The current work entails a reverse genetic approach for deciphering the roles of CBL9 and CIPK23 in the roots of Arabidopsis thaliana (Arabidopsis) during salinity stress. The knockout mutants cbl9 and cipk23 showed salt sensitivity and significantly higher levels of sodium ion (Na+), cytosolic calcium [Ca2+] cyt, and reactive oxygen species (ROS) and an increased death of the cells in root tips compared to the wild-type (WT) under salinity stress (100 mM NaCl). Further, we intended to decipher the effect of salinity stress on the relative expression levels of few key genes that play pivotal role in salinity stress responses and ROS-scavenging activities in the roots of the WT and the mutant seedlings. Compared with the WT, the relative expression levels of the genes in cbl9 and/or cipk23 were significantly augmented (CAX1, 2 and 4, ACA1, CNGC14 and 19, 5PTase2 and DHAR2), attenuated (SOS1, APX1, ALX8, CAT2 and 3, DHAR1, SQD1 and 2) and remained unaffected (NHX1–6 and 8 and GST11). These findings were further corroborated with the increased level of stress markers namely Hydrogen peroxide (H 2 O 2) and Malondialdehyde (MDA) and reduction in chlorophyll, biomass and ascorbate peroxidase (APX) activity in mutants under salt stress condition. The results thus highlighted pivotal roles of CBL9 and CIPK23 on salinity stress responses and ROS-scavenging activities in the roots during salinity stress and a schematic model is presented. [ABSTRACT FROM AUTHOR]