Exogenous calcium (Ca2+) and verapamil-sensitive Ca2+ channel activity differentially modulates melatonin-mediated regulation of endogenous hydrogen sulphide (H2S) homeostasis, and L-cysteine desulfhydrase (L-DES) activity in NaCl-stressed etiolated sunflower seedlings

Abstract

Although Ca2+ has been known to be a modulator of abiotic stress signaling in plants, not much information is available to decipher the interactive roles of calcium and melatonin in mediating hydrogen sulphide homeostasis under NaCl stress. Present work provides evidence on the roles of exogenous calcium (Ca2+) supplementation and endogenous Ca2+ channel activity (verapamil-sensitive) in modulating melatonin-mediated effects on seedling growth and H2S homeostasis in NaCl-stressed sunflower seedlings. In this context, exogenous Ca2+ and verapamil treatments exert differential effects in cotyledons and roots of seedlings raised in the absence and presence of melatonin. On comparing the effects of exogenous Ca2+ supplementation and verapamil-sensitive Ca2+ channel activity, it was observed that exogenous Ca2+exerted differential effects on Mel-H2S signaling in control and NaCl stressed seedlings. Verapamil-sensitive channels seem to be crucial for mediating the effects of exogenous melatonin in sunflower seedlings. Present evidence also indicate that in the absence of exogenous Ca2+, endogenous Ca2+ channel activity and cytosolic Ca2+ milieu are essential for mediating melatonin-H2S signaling in sunflower seedlings. However, it is imperative to undertake future investigations on the probable interaction of melatonin, Ca2+-CaM and other Ca2+-binding proteins as possible regulators of H2S metabolism in plants

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