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See all Premium member Presentation Transcript Understanding & Improving Salt Stress Tolerance in Plants : Understanding & Improving Salt Stress Tolerance in Plants Slide 2: major abiotic stresses affect crop productivity and quality 20% of irrigated agricultural land is adversely affected saline soil : saline soil can be defined as soil having 40 mM NaCl or more Physiological damages : Physiological damages Water deficiency Ion specific stress Ion cyto toxicity Osmotic stress Oxidative damage Slide 4: engineering crops for tolerance to salinity stress is critical for sustaining food production and achieving food security Approaches for enhancing salt tolerance : Approaches for enhancing salt tolerance Exploitation of natural genetic variation 1. Direct selection 2. QTL mapping and MAS Transgenic approaches 1. Introducing novel gene 2. Altering the expression level Transgenic Approaches : Transgenic Approaches Understanding the molecular basis of salt-stress signaling and tolerance mechanisms is essential for genetic engineering of salt tolerance in crop plants How Plants respond to high Na+ concentrations ? : How Plants respond to high Na+ concentrations ? Maintenance of 1. Cellular ion homeostasis Osmotic homeostasis 3. Stress damage control and repair under salt stress How plants sense salt stress ? : How plants sense salt stress ? Ionic stress signals Osmotic stress signals salinity-induced hyper osmotic stress may lead to retraction of the plasma membrane from the cell wall, sensed by both stretch-activated channels and transmembrane protein kinases Trans membrane proteins Membrane proteins within the cell Na+ sensitive enzymes Sodium influx and K/Na balance : Sodium influx and K/Na balance K +/ Na+ ratio Sodium influx : Cation channels (selective & non selective) and low- and high-affinity K+ carriers HKT1 putative regulator of Na + influx Maintanance of K conc. expression of potassium-specific transporters (AKT1). high affinity K+ transporter–K+ uptake genes are up- regulated under NaCl stress Sodium efflux and cellular homeo stasis : Sodium efflux and cellular homeo stasis Sodium efflux from root cells plasma membrane Na+/H+ antiporter, SOS1, plays a crucial role in sodium extrusion from root epidermal cells under salinity Ubiquitously expressed SOS1 transcript level is up-regulated under salt stress Transgenic Arabidopsis over expressing SOS1 are salt resistant (50-200mM) Sodium Compartmentation : Sodium Compartmentation +ve turgor pressure for cell growth Water potential Osmotic stress Turgor loss Osmotic adjustment (active solute accumulation) mechanism that maintains water uptake and turgor under osmotic stress conditions Vacuolar sequestration of Na+ Na+/H+ antiporter V-type H+-ATPase & H+-PPase Synthesis of Compatible Osmotytes : Synthesis of Compatible Osmotytes To accommodate the ionic balance low-molecular-mass compounds compatible solutes do not interfere with normal biochemical reactions Basic functions: osmotic adjustment osmoprotection In osmotic adjustment, they act as osmolytes facilitating the retention of water in the cytoplasm and allowing sodium sequestration to the vacuole or apoplast. These osmolytes protect cellular structures by interacting with membranes, protein complexes, or enzymes. These compounds have hydrogen-bonding characteristics that allow them to protect macromolecules from the adverse effects of increasing ionic strength in the surrounding media Stress damage control by ROS scavenging : Stress damage control by ROS scavenging Water deficit reactive oxygen species (ROS) : super oxide, hydrogen peroxide, hydroxyl radical & singlet oxygen Cytotoxic oxidative damage to lipids , protein and nucleic acids Antioxidants: ascorbate, glutathione, -tocopherol, and carotenoids Enzymes: catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) Overexpression of a plasma membrane Na+/H+ antiporter gene improves salt tolerance in Arabidopsis thalianaHuazhong Shi, Byeong-ha Lee, Shaw-Jye Wu & Jian-Kang Zhu : Overexpression of a plasma membrane Na+/H+ antiporter gene improves salt tolerance in Arabidopsis thalianaHuazhong Shi, Byeong-ha Lee, Shaw-Jye Wu & Jian-Kang Zhu Arabidopsis (Columbia variety) Vacuum infiltration: GV3101 You do not have the permission to view this presentation. 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