Abstract: Objective: This study aimed to investigate whether melatonin treatment could induce the expression of stilbene synthase (sts) genes and thereby enhance content of resveratrol in grapevine. Methods: The whole grape clusters were treated with 100 μmol/L melatonin at early veraison, and the roots of in vitro shoot cultures were treated with 30 μmol/L melatonin for approximately 30 days after subculture. RNA-Seq with the grape genome data as a reference was employed to identify melatonin-induced sts genes. Sequence and clustering analysis were performed using Clustalx and MEGA5 software, and the cis-acting elements in the promoter region were identified using online plantCARE software. The expression levels of sts genes were detected using quantitative real-time PCRs. The content of resveratrol was determined by high performance liquid chromatography (HPLC). Results: RNA-Seq analysis showed that 30 sts genes were up-regulated by melatonin treatment, accounting for 62.5% of the total amount of grape sts genes and 8.5% of all the up-regulated genes. The melatonin-induced sts genes were primarily located in chromosome 16 and their deduced proteins shared more than 88.3% similarity; only one different amino acid existed between the two sts with the highest similarity. The promoter regions of different sts genes were also highly conserved and their similarity surpassed 55.6%. The detected 30 sts genes were clustered into three groups, i.e., A, B and C, in the light of their sequence similarity of protein or promoter. A highly conserved sequence was found in the promoters of sts genes from groups A and B. Additionally, there were a number of cis-acting elements present in the promoters of sts gens related to ABA-, ethylene-, salicylic acid- and auxin-responsive elements. The 30 melatonin-induced sts genes exhibited varying expression patterns in different tissues and generally they were predominantly expressed in grape roots; additionally, they had varying transcriptional abundance in grape berries. qRT-PCR analysis showed that the 5 selected sts gens were induced by melatonin, consistent with the results of RNA-Seq, and exhibited different expression patterns in response to melatonin. Conclusions: A total of 30 sts genes were induced by melatonin in grape berries and they shared highly conserved protein and promoter sequences. The promoter regions of 30 sts gens contained different cis-acting elements and they exhibited different expression patterns in response to melatonin treatment. Melatonin treatment enhanced the content of resveratrol in grape berries and roots. The results of this study laya basis for the application of melatonin in improving the nutritional value of grape berries and shed light on the molecular mechanism underlying the regulation of melatonin on resveratrol metabolism

Key words: grape, sts, sequence characteristics, expression analysis, resveratrol