Sinalização celular por gastransmissores em plantas de Solanum lycopersicum desafiadas com estresse salino

Abstract

Salt excess is detrimental to plant growth and production as it induces water deficit, and osmotic, ion, and oxidative stress. A signaling cascade involving phytohormones, some ions, and gasotransmitters such as nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) is activated in plants capable of responding to salt stress. This work aimed to investigate the contribution of NO, CO, and H2S to the response of Solanum lycopersicum genotypes Micro-Tom and Micro-Tom-yg2 and a possible correlation with a transient suppression of Ca2+ e Mg2+ to roots. Differently from MT-yg2, MT roots showed an increase in the NO levels 30 min after treatment with 100 mM NaCl. However, the treatment of roots with NaCl for 48 h did not increase NO levels. MT e MT-yg2 roots produce CO in amounts that are not affected by the treatment with NaCl for 48 h. The suppression of Ca2+ and Mg2+ in roots of plants under NaCl treatment caused a decrease in NO and an increase in CO levels. The increase in CO levels, however, was not accompanied by an increment of heme oxygenase (HO) activity, suggesting that other pathways are activated to account for the increased CO production. The fluorescence technique used herein failed to properly quantify H2S in plant samples. L-proline increased in the roots and leaves of MT and MT-yg2 plants upon NaCl treatment. Roots from both genotypes under NaCl treatment in the absence of Ca2+ and Mg2+ presented L-proline levels compared to those of control plants while this same treatment caused an increment in L-proline in the leaves. Part of the L-proline present in roots may be translocated to leaves and the Ca2+ and Mg2+ depletion in roots may not be sensed in shoots as leaves likely present enough amounts of Ca2+ and Mg2+ obtained along with plant growth in nutrient solution. The phenotype severity shown by MT and MT-yg2 plants upon NaCl for 48 h in the absence of Ca2+ and Mg2+ indicates that such cations are indispensable in the cell signaling cascade that confers to tomatoes the tolerance to salt stress.