Mammalian neurohormones: potential significance in reproductive physiology of St. John's wort (Hypericum perforatum L.)?

Abstract

Melatonin and serotonin are indoleamine neurohormones that function as photoperiod signals in many species and have recently been found in St. John's wort, a medicinal plant used in the treatment of depression. There is no known role for melatonin in higher plants but melatonin functions as a signal of changes in photoperiod in other species. In the current study, serotonin and melatonin were quantified during flower development. Higher concentrations of serotonin were found in flower buds at the tetrad stage of microspore development and higher melatonin concentrations were detected during uninucleate mircosporogenesis. Additionally, the regeneration potential of isolated anthers was highest in the same stage that had elevated melatonin concentrations. These data provide the first evidence of the presence of melatonin during flower development and raise many questions about the potential roles of serotonin and melatonin as regulatory molecules in the reproductive flexibility of higher plants.

Circadian changes in endogenous concentrations of indole-3-acetic acid, melatonin, serotonin, abscisic acid and jasmonic acid in Characeae (Chara australis Brown)

“…These are large changes for melatonin and serotonin, but surveys of various fruits and whole plants show huge range of concentrations from mg/g to pg/g of tissue. 15 In the same tissue a substancial drop in melatonin and serotonin levels were observed in developing flower buds of D. metel, especially if the plants were exposed to cold stress. 27 Large changes in endogenous IAA levels (680 to 6 ng/g of tissue) were measured in Lemna gibba L. during 45 day growth cycle.…”

“…11,12 Murch et al 13 described its synthesis from tryptophan via pathway that can also produce IAA. 14,15 It is now thought that similar to ABA, melatonin is of ancient origin, introduced into both plant and animal kingdoms through cyanobacteria and proteobacteria that became, respectively, chloroplasts and mitochondria. 16 The genetic basis and regulation of the synthesis of melatonin in plants are now probed by molecular techniques.…”

Hypericum perforatum L. supplementation protects sciatic nerve injury-induced apoptotic, inflammatory and oxidative damage to muscle, blood and brain in rats

“…[14,18,39] HPL administration caused an increased level of blood melatonin in human. [41,42] In addition to exogenous production of OFR, most of the OFR are a result of mitochondrial respiratory chain pathways. [29] HPL has an important role in scavenging the OFR production in the mitochondria.…”

Arabidopsis Transcriptome Analysis Reveals Key Roles of Melatonin in Plant Defense Systems

“…Contradicting reports of melatonin levels in ripening fruits add to the variation observed among plant species; melatonin levels decreased in ripening cherries [20], but increased in ripening tomatoes [18]. The possible role of melatonin in regulating flowering has also been investigated [23]–[25]; however an unequivocal role of melatonin in photoperiod-dependent processes in plants has not yet been established…”