HsfA1a upregulates melatonin biosynthesis to confer cadmium tolerance in tomato plants

Abstract

Melatonin regulates broad aspects of plant responses to various biotic and abiotic stresses, but the upstream regulation of melatonin biosynthesis by these stresses remains largely unknown. Herein, we demonstrate that transcription factor heat-shock factor A1a (HsfA1a) conferred cadmium (Cd) tolerance to tomato plants, in part through its positive role in inducing melatonin biosynthesis under Cd stress. Analysis of leaf phenotype, chlorophyll content, and photosynthetic efficiency revealed that silencing of the HsfA1a gene decreased Cd tolerance, whereas its overexpression enhanced plant tolerance to Cd. HsfA1a-silenced plants exhibited reduced melatonin levels, and HsfA1a overexpression stimulated melatonin accumulation and the expression of the melatonin biosynthetic gene caffeic acid O-methyltransferase 1 (COMT1) under Cd stress. Both an in vitro electrophoretic mobility shift assay and in vivo chromatin immunoprecipitation coupled with qPCR analysis revealed that HsfA1a binds to the COMT1 gene promoter. Meanwhile, Cd stress induced the expression of heat-shock proteins (HSPs), which was compromised in HsfA1a-silenced plants and more robustly induced in HsfA1a-overexpressing plants under Cd stress. COMT1 silencing reduced HsfA1a-induced Cd tolerance and melatonin accumulation in HsfA1a-overexpressing plants. Additionally, the HsfA1a-induced expression of HSPs was partially compromised in COMT1-silenced wild-type or HsfA1a-overexpressing plants under Cd stress. These results demonstrate that HsfA1a confers Cd tolerance by activating transcription of the COMT1 gene and inducing accumulation of melatonin that partially upregulates expression of HSPs.

High Concentration of Melatonin Regulates Leaf Development by Suppressing Cell Proliferation and Endoreduplication in Arabidopsis

“…The extensive transcriptional reprogramming is consistent with the wide participation of melatonin in plant stress resistance, at least partially [11,12,13,14,15,16,17,18,19,20,21,22]. On the other hand, melatonin is also involved in several developmental processes of plants, including seed germination, shoot development, root growth and architecture, flowering and fruit ripening [23,24,25,26,27,28,29].…”

“…[7,8,9,10]. In the most recent 20 years, studies on melatonin have revealed that it functions as an important messenger in regulating the response of plant to both abiotic and biotic stresses, including cold, heat, salt, drought, cadmium, zinc sulfate, and pathogen attacks [11,12,13,14,15,16,17,18,19,20,21,22]. Melatonin also participates in the processes of root growth and architecture, shoot development, flowering, seed germination and fruit ripening [23,24,25,26,27,28,29].…”

Flavonoids inhibit both rice and sheep serotonin N‐acetyltransferases and reduce melatonin levels in plants

“…Caffeic acid O ‐methyltransferase is a key enzyme of plant melatonin biosynthesis, converting N ‐acetylserotonin to melatonin (Figure A) . As the enzyme accepts various substrates, melatonin synthesis featuring COMT action would be inhibited by other COMT substrates such as quercetin .…”

Melatonin delays leaf senescence of Chinese flowering cabbage by suppressing ABFs‐mediated abscisic acid biosynthesis and chlorophyll degradation

“…In vivo melatonin was extracted from ~1.0 g frozen cabbage leaves and quantified by high‐performance liquid chromatography‐mass spectrometry (HPLC‐MS) on an Agilent 6460 Triple Quad LC/MS with an Agilent‐XDB C 18 column (2.1 mm × 150 mm) as described by Cai et al…”