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

Abstract

Giant-celled Characeae (Chara australis Brown), grown for 4 months on 12/12 hr day/night cycle and summer/autumn temperatures, exhibited distinct concentration maxima in auxin (indole-3-acetic acid; IAA), melatonin and serotonin about 4 hr after subjective daybreak. These concentration peaks persisted after 3 day pretreatment in continuous darkness: confirming a circadian rhythm, rather than a response to "light on." The plants pretreated for 3 d in continuous light exhibited several large IAA concentration maxima throughout the 24 hr. The melatonin and serotonin concentrations decreased and were less synchronized with IAA. Chara plants grown on 9/15 hr day/night cycle for 4 months and winter/spring temperatures contained much smaller concentrations of IAA, melatonin and serotonin. The IAA concentration maxima were observed in subjective dark phase. Serotonin concentration peaks were weakly correlated with those of IAA. Melatonin concentration was low and mostly independent of circadian cycle. The "dark" IAA concentration peaks persisted in plants treated for 3 d in the dark. The plants pretreated for 3 d in the light again developed more IAA concentration peaks. In this case the concentration maxima in melatonin and serotonin became more synchronous with those in IAA. The abscisic acid (ABA) and jasmonic acid (JA) concentrations were also measured in plants on winter regime. The ABA concentration did not exhibit circadian pattern, while JA concentration peaks were out of phase with those of IAA. The data are discussed in terms of crosstalk between metabolic pathways.

A new balancing act: The many roles of melatonin and serotonin in plant growth and development

“…Nevertheless, MEL content has been found to vary in some species of plant seasonally and also on a daily basis suggesting that even if it is not a primary chronoregulator in plants, it plays a role in timing both chronoregulatory processes and reproductive development 36,44 . Additionally in several cases, this rhythm was maintained even when plants were kept in the dark, confirming endogenous maintenance of this system 117,118 . One possibility is that the MEL content is synchronized, with photosynthetic activity with daylight as the photosynthetic process producing large quantities of dangerous free radicals and reactive oxygen species 4,43,119,120 .…”

Determining diurnal and seasonal changes in melatonin andtryptophan contents of eggplant (Solanum melongena L.)

“…Melatonin is reported to be a molecule having an auxinic activity, where it promotes and inhibits vegetative growth in a similar fashion to IAA (Hernández-Ruiz et al, 2005). Moreover, synchronous circadian concentration changes (double peaks in a 24-h duration) in melatonin, serotonin, and IAA, all of which are produced from the same precursor, tryptophan, are reported in the family Characeae, indicating a possible crosstalk between IAA and melatonin biosynthesis pathways (Beilby et al, 2015).…”

On plant defense signaling networks and early land plant evolution

“…[94,111-114]]; yet we are only beginning to understand the function of these phytohormones in streptophyte algae [115-117]. All three canonical plant defense phytohormones, JA, SA and ET, have been detected in at least some species of streptophyte algae [94,112,115,118]. They also have been explored with regard to pathogen defense in non-flowering land plants.…”

“…However, actual (mainly mass spectrometry-based) measurements of JA levels are suggestive of a patchier distribution among land plants and streptophyte algae. For example, while JA is reported to be produced in small quantities in the streptophyte algae K. nitens [94] and Chara australis [118], Hackenberg and Pandey [126] did not detect JA in Chara braunii . Furthermore, Gachet et al [127] did not detect JA in Chara vulgaris and Klebsormidium elegans , while Koeduka et al [128] found only minimal levels of JA in Klebsormidium flaccidum .…”