In plants dehydration imposed by salinity can invoke physical changes at the interface of the plasma membrane and cell wall. Changes in hydrostatic pressure activate ion channels and cause depolarization of the plasma membrane due to disturbance in ion transport. During the initial phases of salinity stress, the relatively high osmotic potential of the rhizosphere enforces the plant to use a diverse spectrum of strategies to optimize water and nutrient uptake. Signals of salt stress are recognized by specific root receptors that activate an osmosensing network. Plant response to hyperosmotic tension is closely linked to the calcium (Ca 2+) channels and interacting proteins such as calmodulin. A rapid rise in cytosolic Ca 2+ levels occurs within seconds of exposure to salt stress. Plants employ multiple sensors and signaling components to sense and respond to salinity stress, of which most are closely related to Ca 2+ sensing and signaling. Several tolerance strategies such as osmoprotectant accumulation, antioxidant boosting, polyaminses and nitric oxide (NO) machineries are also coordinated by Ca 2+ signaling. Substantial research has been done to discover the salt stress pathway and tolerance mechanism in plants, resulting in new insights into the perception of salt stress and the downstream signaling that happens in response. Nevertheless, the role of multifunctional components such as Ca 2+ has not been sufficiently addressed in the context of salt stress. In this review, we elaborate that the salt tolerance signaling pathway converges with Ca 2+ signaling in diverse pathways. We summarize knowledge related to different dimensions of salt stress signaling pathways in the cell by emphasizing the administrative role of Ca 2+ signaling on salt perception, signaling, gene expression, ion homeostasis and adaptive responses.

No abstract

No abstract

Gamma-Aminobutyric acid (GABA) accumulates in plants following exposure to heavy metals. to investigate the role of GABA in cadmium (cd) tolerance and elucidate the underlying mechanisms, GABA (0, 25 and 50 µM) was applied to cd-treated maize plants. Vegetative growth parameters were improved in both cd-treated and control plants due to GABA application. cd uptake and translocation were considerably inhibited by GABA. Antioxidant enzyme activity was enhanced in plants subjected to cd. concurrently GABA caused further increases in catalase and superoxide dismutase activities, which led to a significant reduction in hydrogen peroxide, superoxide anion and malondealdehyde contents under stress conditions. polyamine biosynthesis-responsive genes, namely ornithine decarboxylase and spermidine synthase, were induced by GABA in plants grown under cd shock. GABA suppressed polyamine oxidase, a gene related to polyamine catabolism, when plants were exposed to Cd. Consequently, different forms of polyamines were elevated in Cd-exposed plants following GABA application. The maximum quantum efficiency of photosystem II (F v /f m) was decreased by cd-exposed plants, but was completely restored by GABA to the same value in the control. these results suggest a multifaceted contribution of GABA, through regulation of cd uptake, production of reactive oxygen species and polyamine metabolism, in response to cd stress. Heavy metal (HM) toxicity is considered a major threat to living organisms. HM-polluted soils derived from increasing geologic and anthropogenic activities have significantly impacted the production of high-quality agricultural crops in certain regions of the world. Plants growing on these soils exhibit reduced growth, photosynthetic performance, and yield 1. As a naturally occurring HM pollutant, Cd exposure has been documented in most organisms, particularly plants and humans 2. World fertilizer consumption is increasing and will eventually reach a point where the drawbacks outweigh the benefits 3. The same mechanisms that drive improved plant productivity often create side effects such as environmental contamination. Furthermore, some components of fertilizers, especially Cd, accumulate in both body and food chain, where they remain for an extended period and causes adverse health effects 4. Therefore, fertilizers containing very high levels of Cd (417 mg/kg) threaten human health by accumulation in important crop such as maize 5. Maize, as one of the most popular cereal grain, is widely cultivated across the world. Maize is also produced at an industrial scale as a key input in various products such as syrups, soft drinks and charcoals 6,7. Therefore, there is a strong incentive to minimize the toxic effects of Cd in maize.

No abstract