title: Salt stress-induced seedling growth inhibition coincides with differential distribution of serotonin and melatonin in sunflower seedling roots and cotyledons.
abstract: Indoleamines regulate a variety of physiological functions during the growth, morphogenesis and stress-induced responses in plants. Present investigations report the effect of NaCl stress on endogenous serotonin and melatonin accumulation and their differential spatial distribution in sunflower (Helianthus annuus) seedling roots and cotyledons using HPLC and immunohistochemical techniques, respectively. Exogenous serotonin and melatonin treatments lead to variable effect on hypocotyl elongation and root growth under NaCl stress. NaCl stress for 48 h increases endogenous serotonin and melatonin content in roots and cotyledons, thus indicating their involvement in salt-induced long distance signaling from roots to cotyledons. Salt stress-induced accumulation of serotonin and melatonin exhibits differential distribution in the vascular bundles and cortex in the differentiating zones of the primary roots, suggesting their compartmentalization in the growing region of roots. Serotonin and melatonin accumulation in oil body rich cells of salt-treated seedling cotyledons correlates with longer retention of oil bodies in the cotyledons. Present investigations indicate the possible role of serotonin and melatonin in regulating root growth during salt stress in sunflower. Effect of exogenous serotonin and melatonin treatments (15 μM) on sunflower seedlings grown in the absence or presence of 120 mM NaCl substantiates their role on seedling growth. Auxin and serotonin biosynthesis are coupled to the common precursor tryptophan. Salt stress-induced root growth inhibition, thus pertains to partial impairment of auxin functions caused by increased serotonin biosynthesis. In seedling cotyledons, NaCl stress modulates the activity of N-acetylserotonin O-methyltransferase (HIOMT; EC 2.1.1.4), the enzyme responsible for melatonin biosynthesis from N-acetylserotonin.
authors.affiliation: Laboratory of Plant Physiology and Biochemistry, Department of Botany, University of Delhi, Delhi, 110007, India.
authors.forename: Soumya
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Anisha
authors.initials: A
authors.lastname: David
authors.forename: Sunita
authors.initials: S
authors.lastname: Yadav
authors.forename: František
authors.initials: F
authors.lastname: Baluška
authors.forename: Satish Chander
authors.initials: SC
authors.lastname: Bhatla
mesh_terms: D018548:Cotyledon / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D006368:Helianthus / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D018546:Hypocotyl / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D007210:Indoleacetic Acids / Q000378:metabolism; D008550:Melatonin / Q000378:metabolism* / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D012701:Serotonin / Q000378:metabolism* / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological
chemical_list: D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D012701:Serotonin; D012965:Sodium Chloride; D008550:Melatonin