Serotonin and Melatonin Biosynthesis in Plants: Genome-Wide Identification of the Genes and Their Expression Reveal a Conserved Role in Stress and Development.

Bidisha Bhowal,Sneh L Singla-Pareek,Kavita Goswami,Neeti Sanan-Mishra,Sudhir Sopory,Charanpreet Kaur,Annapurna Bhattacharjee

doi:10.3390/ijms222011034

Abstract

Serotonin (Ser) and melatonin (Mel) serve as master regulators of plant growth and development by influencing diverse cellular processes. The enzymes namely, tryptophan decarboxylase (TDC) and tryptamine 5-hydroxylase (T5H) catalyse the formation of Ser from tryptophan. Subsequently, serotonin N-acetyl transferase (SNAT) and acetyl-serotonin methyltransferase (ASMT) form Mel from Ser. Plant genomes harbour multiple genes for each of these four enzymes, all of which have not been identified. Therefore, to delineate information regarding these four gene families, we carried out a genome-wide analysis of the genes involved in Ser and Mel biosynthesis in Arabidopsis, tomato, rice and sorghum. Phylogenetic analysis unravelled distinct evolutionary relationships among these genes from different plants. Interestingly, no gene family except ASMTs showed monocot- or dicot-specific clustering of respective proteins. Further, we observed tissue-specific, developmental and stress/hormone-mediated variations in the expression of the four gene families. The light/dark cycle also affected their expression in agreement with our quantitative reverse transcriptase-PCR (qRT-PCR) analysis. Importantly, we found that miRNAs (miR6249a and miR-1846e) regulated the expression of Ser and Mel biosynthesis under light and stress by influencing the expression of OsTDC5 and OsASMT18, respectively. Thus, this study may provide opportunities for functional characterization of suitable target genes of the Ser and Mel pathway to decipher their exact roles in plant physiology.

Highlights

Serotonin (Ser) and melatonin (Mel) are indoleamines which are synthesised in most life forms including prokaryotes such as bacteria, as well as fungi, nematodes, animals and plants; their presence in archaea remains to be studied [1]
In the current study, we have attempted to identify the genes involved in Ser and Mel biosynthesis in four model plant species, namely, Arabidopsis, rice, sorghum and tomato, followed by analysis of their evolutionary relationships
Genes encoding enzymes for Ser and Mel biosynthesis were identified from rice, Arabidopsis, tomato and sorghum, as described in the Materials and Methods section

Summary

Introduction

Serotonin (Ser) and melatonin (Mel) are indoleamines which are synthesised in most life forms including prokaryotes such as bacteria, as well as fungi, nematodes, animals and plants; their presence in archaea remains to be studied [1]. They are well known neurotransmitters, which play vital roles, especially in animals, being associated with diverse physiological processes. Cells containing high tryptophan levels, generally, accumulate greater amounts of Ser and, subsequently, Mel [8]. According to the classical pathway, tryptophan decarboxylase (TDC) and (TDC) and tryptamine 5-hydroxylase (T5H) enzymes are required

Methods

Results

Discussion

Conclusion