Signal Perception and Mechanism of Salt Toxicity/Tolerance in Photosynthetic Organisms: Cyanobacteria to Plants

Abstract

High salt concentration represents one of the most significant abiotic constraints, affecting all life forms including plants and cyanobacteria. Soil salinity curtails plant growth by way of osmotic, ionic and oxidative stresses resulting in multiple inhibitory effects on various physiological processes such as growth, photosynthesis, respiration and cellular metabolism. In order to combat high salinity, various adaptive strategies employed include ion homeostasis achieved by ion transport and compartmentalization of injurious ions, osmotic homeostasis by accumulation of compatible solutes/osmolytes and upregulation of antioxidant defence mechanism. The aforesaid processes are executed through SOS and MAPK signalling pathways leading to modulation of gene expression. Salt stress signal transduction pathways initiate through sensing extracellular Na + ions causing modification of constitutively expressed transcription factors. This modification is responsible for expression of early transcriptional activators such as CBF/DREB gene family which eventually activate stress tolerance effector genes such as osmolyte biosynthesis genes, detoxification enzymes, and chaperones. Various genes/cDNAs encoding proteins involved in these adaptive mechanisms have been isolated and identified. Bioinformatic predictions through docking revealed interaction of salt across the species at conserved domains and motifs as a possible mechanism for response of a particular protein under salt stress. In this chapter, major aspects of salt stress are reviewed with emphasis on its detrimental consequences and biochemical and molecular mechanisms of signal transduction in plants and cyanobacteria under high salinity.

Comprehensive evaluation of morphological and physiological responses of seventeen Sedum species to waterlogging and drainage under temperate monsoon climate: photosynthesis, osmotic balance and antioxidant capacity

“…A su cient water content is bene cial for subcellular structural stabilization and cell recovery from stress. Waterlogging often reduces plant RWC (Balakhnina 2015;Haddadi et al 2016), as demonstrated in the current study. Prolonged waterlogging reduced relative water content dramatically (Fig.…”

“…All of these waterlogging stress-induced adaptations aid in the capture and diffusion of oxygen (Kitomi et al, 2020) Plants have mechanisms to cope with this stress in addition to the adaptations mentioned above, such as increased availability of soluble sugars, increased activity of glycolytic pathway and fermentation enzymes, and involvement of antioxidant defense mechanism to cope with post hypoxia/anoxia oxidative stress (Sairam et al 2008;Silva et al 2017). Soluble sugar acts as an osmotic agent or osmoprotector, protecting the structural integrity of proteins and membranes under abiotic circumstances (Béjaoui et al 2016;Balakhnina 2015). In fact, the quantity of stored carbohydrates and their accessibility may distinguish between tolerant and intolerant species.…”

“…These effects can include a loss of enzyme activity, altered membrane uidity, genomic damage, and even cell death (Finkel and Holbrook 2000;Striker and Colmer 2017). An endogenous antioxidant defense system, which is made up of antioxidative enzymes like superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), as well as non-enzymatic antioxidants, is responsible for scavenging ROS in order to reduce oxidative damage when the organism is under stress (Balakhnina 2015). Numerous studies have also documented the activity of antioxidant enzymes in response to diverse environmental conditions (Haddadi et al 2016;Zhao et al 2022).…”

“…Numerous studies have also documented the activity of antioxidant enzymes in response to diverse environmental conditions (Haddadi et al 2016;Zhao et al 2022). Malondialdehyde (MDA), a byproduct of the lipoperoxidation of cell membranes, is a biomarker of oxidative stress that can be used to determine how susceptible an individual is to waterlogging (Balakhnina, 2015).…”

Polyphosphate fertilizer impacts the enzymatic and non-enzymatic antioxidant capacity of wheat plants grown under salinity

“…Under salt stress, polyphosphates and orthophosphates can also assist in regulating ion homeostasis in plant cells 126 . Excessive salt can damage cells and cause oxidative stress by upsetting the equilibrium of ions inside and outside plant cells 125 .…”