Salt-induced gasotransmitters signaling in two Solanum lycopersicum micro-tom genotypes

Abstract

The increase in soil salinity is a detrimental environmental stressor to plant growth and productivity as it disrupts nutrient metabolism and assimilation. Antioxidant enzymes play crucial roles in the response to salinity stress, and a cascade of cellular signaling is stimulated to regulate and repair the antioxidant system, such as gasotransmitters, nitric oxide (NO), hydrogen sulfide (H2S), and carbon monoxide (CO). Melatonin also plays a significant role in mediating physiological processes and is involved in signaling environmental changes and detoxifying free radicals. This study aimed to assess the role of NO, H2S, CO, and melatonin in cellular signaling in response to salt stress in tomato (Solanum lycopersicum L.), and to elucidate their interrelations and associations with nutrient transport in cells and protection under saline stress conditions in Micro-Tom (MT) and Micro-Tom yellow-green (MT-yg2) genotypes and differentiate them, since MY-yg2 genotype is defective for heme oxygenase 1 (HO1). Thus, the activity of the antioxidant system, the production of gasotransmitters, and the effect of melatonin were evaluated. It was observed that the activity of the enzyme Heme oxygenase (HO) increased 2.7 times in MT leaves in the presence of treatment with 100mM NaCl in plants treated for 48 hours, treatment of MT with NaCl for 2 hours resulted in decreased activity of ascorbate peroxidase (APX), catalase (CAT) by 38%, and superoxide dismutase (SOD) by 32% in roots, while the activity of the same enzymes increased by 40% in APX and CAT and 9.4% in SOD in MT-yg2 leaves under the same conditions. The concentration of lipid hydroperoxides (LOOH) decreased by 17.4% in MT leaves treated with melatonin, while simultaneous treatment of MT-yg2 roots with NaCl and melatonin resulted in about 10% more LOOH in the plant leaves. CO production decreased in MT roots treated with NaCl, while melatonin led to a 75% increase in CO production in MT roots. H2S levels and mineral nutrient translocation to the leaves were not affected in roots treated with NaCl. NO production decreased by 57% in NaCl-challenged MT-yg2 roots. Overall, MT tomatoes tolerated the high imposed salinity possibly due to their ability to translocate NO and other gasotransmitters from roots to leaves, stimulating the antioxidant system. HO-1 defective tomatoes (MT-yg2) showed sensitivity to 100 mM NaCl, partially mitigated by treatment with 0.1 mM melatonin. Melatonin, NO, H2S, and CO were demonstrated to play an important role in tomato response to high salinity.