Exogenous Serotonin Improves Drought and Salt Tolerance in Tomato Seedlings

Abstract

Abstract Serotonin and melatonin, which are indolamines present in every biological kingdom, show strong bioregulator activity in plant tissues under various stress conditions. Although numerous studies report stress mitigating effects of melatonin, effect of serotonin on plant stress physiology was rarely studied in the current literature. In this study, effects of exogenous serotonin application on tomato seedlings under severe salt and drought stresses were investigated by examining various morphological and physiological plant stress indicators, including tissue length and mass, relative water content (RWC), ion leakage, malonedialdehyde (MDA) and proline content, as well as some oxidative stress related gene activities, ascorbate peroxidase (APX1), superoxide dismutase (FeSOD), catalase (CAT2), gluthatione reductase (GR1), delta 1-pyrroline-5-carboxylate synthase (P5CS) and 1-aminocyclopropane-1-carboxylic acid synthase 2 (ACS2). Our results showed that serotonin application decreased tissue MDA contents and ion leakage levels, whereas increased relative water contents of tomato plants under both stresses. Serotonin also decreased ACS2 gene expression, meanwhile increased FeSOD, CAT2, GR1 and P5CS gene expressions under salt and drought stresses. Our findings showed that similar to its close chemical relative melatonin, serotonin also exhibits stress mitigation effects and boosts the antioxidant capacity of tomato plants under most common abiotic stress conditions.