Nitric Oxide and High Temperature Stress: A Physiological Perspective

Abstract

High temperature stress is one the devastating abiotic stresses, causing severe damage to each stage of plant growth and development. However, to cope with detrimental effects of heat stress plants are equipped with a system of defense orchestrated by a combination of several sensor proteins, heat shock factors (HSFs), heat-shock proteins (HSPs), antioxidant enzymes and signaling molecules. Precise assessment of rising temperature at cellular level is of vital importance to induce defense system of plant before the onset of heat damage. Plants sense heat stress primarily by plasma membrane-enclosed sensors which generate a heat stress response that induces a downstream signal leading to the expression of stress-responsive genes. Nitric oxide (NO), along with abscisic acid, H2O2, Ca2+, and calmodulin (CaM), acts as an important signaling molecule in heat stress response in plants. Heat stress elevates synthesis of NO which in association with these molecules stimulate the DNA-binding activity of HSFs as well as the accumulation of HSPs leading to resistance to heat stress. Moreover, exogenous application of NO has also been shown to have an ameliorative effect on heat stress, which has been confirmed by several studies using NO scavengers and inhibitors. In the present chapter, the current understanding of the involvement of NO in heat stress and in the mechanism of thermotolerance is reviewed.