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DNA methylation plays essential roles in gene regulation, chromatin structure stability, gene imprinting, X chromosome inactivation and embryonic development. However, the dynamics and functions of DNA methylation during the early stage of longan (Dimocarpus longan) somatic embryogenesis (SE) are still unclear. In this study, we carried out whole genome bisulphite sequencing and transcriptome sequencing analyses for embryogenic callus (EC), incomplete compact pro-embryogenic cultures (ICpEC) and globular embryos (GE) in an early SE system. At a global level, the DNA 5-methylcytosine content in EC, ICpEC and GE was 24.59, 19.65 and 19.74%, respectively, suggesting a global decrease in DNA methylation from EC to ICpEC and then a slight increase from ICpEC to GE. Differentially methylated region (DMR) analysis showed that hypomethylation mainly occurred in CHH contexts. Gene ontology and Kyoto encyclopedia of genes and genomes analysis of hypomethylated-CHH-DMR-associated genes revealed that zein biosynthesis, fatty acid biosynthesis, circadian rhythm and mitophagy pathways were involved in longan early SE. Expression patterns of DNA methyltransferase and demethylase genes during longan early SE suggested that the decrease in DNA methylation was probably regulated by DNA methyltransferase genes and the DNA demethylase gene REPRESSOR OF SILENCING 1 (ROS1). The correlation between DNA hypomethylation and gene expression revealed that decreased DNA methylation did not cause extensive changes in gene expression during early longan SE and that gene expression may be affected by methylation changes in gene and downstream regions. Inhibiting DNA methylation with 5-azacytidine treatment in EC promoted the formation of GE and enhanced the capability of longan SE. Our results suggest that DNA demethylation has important roles in longan SE development. [ABSTRACT FROM AUTHOR]

To investigate differences in secondary metabolites and their related molecular mechanisms between purple-leaf tea and green-leaf tea, the transcriptomes and the secondary product profiles of the Camellia sinensis cultivars 'Hongyafoshou' (HF) and cultivar 'Lvyafoshou' (LF) were analysed and compared using GC-MS and spectrophotometric methods. The contents of anthocyanins, carotenoids, and total catechins were higher in HF than in LF. In total, 8,406 differentially expressed genes (DEGs) between HF and LF were identified. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that the flavonoids, carotenoids and terpenoids metabolic pathways were highly enriched with DEGs. Differences in the expression of DEGs involved in these three pathways might be responsible for the high accumulation of secondary metabolites in HF. The small miRNA miR529 plays regulatory roles in these secondary metabolic pathways. The sensory quality of purple-leaf tea is higher than that of green-leaf tea, and these results from the combination of flavonoids, carotenoids, and terpenoids biosynthesis. Our study provides further insights into the molecular mechanisms underlying differences in secondary metabolite accumulation between HF and LF. [ABSTRACT FROM AUTHOR]