Abstract
BackgroundThe anthocyanins are highly enriched in eggplants (Solanum melongena L.) with purple peel. However, our previous study showed that anthocyanins biosynthesis in eggplant cultivar ‘Lanshan Hexian’ was completely regulated by light and color becomes evident at most 2 days after exposure to light. In the present investigation, transcriptome study was made to explore the underlying molecular mechanisms of light-induced anthocyanin biosynthesis in eggplant (Solanum melongena L.) before color becomes evident.ResultsRNA-Seq was performed for four time points (0, 0.5, 4 and 8 h after bags removal) where concerted changes happened. A total of 32,630 genes or transcripts were obtained by transcriptome sequencing, from which 1956 differentially expressed genes (DEGs) were found. Gene Ontology analysis showed that the 1956 DEGs covered a wide range of cellular components, molecular functions and biological processes. All the DEGs were further divided into 26 clusters based on their distinct expression patterns. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis found out 24 structural anthocyanin biosynthesis genes which distributing in seven clusters. In addition, 102 transcription factors, which exhibited highly dynamic changes in response to light, were found in the seven clusters. Three photoreceptors, UV Resistance Locus 8 (UVR8), Cryptochrome 3 (CRY3) and UVR3, were identified as DEGs. The light signal transduction elements, COP1 and two SPAs, might be responsible for anthocyanin biosynthesis regulation.ConclusionBased on the transcriptome data, the anthocyanin biosynthesis structural genes, transcription factors, photoreceptors and light signal transduction elements were quickly screened which may act as the key regulatory factors in anthocyanin biosynthesis pathway. By comparing the transcriptome data with our previous studies, 869 genes were confirmed to participate in the light-induced anthocyanin biosynthesis. These results expand our knowledge of light-induced anthocyanin biosynthesis in plants, which allowing for fruit coloration to be improved under low-light conditions in future.
Highlights
The anthocyanins are highly enriched in eggplants (Solanum melongena L.) with purple peel
Anthocyanin biosynthesis structural genes were induced by light within an 8 h exposure period The transcriptions of CRY1, CRY2, Hypocotyl 5 (HY5) and MYB1 were previously shown to be triggered by exposure to light over an 8 h period [5]
The expression levels of six anthocyanin biosynthesis structural genes (CHS, chalcone isomerase (CHI), flavanone 3-hydroxyl enzyme (F3H), F3’5’H, dihydroflavonol reductase (DFR) and anthocyanin synthase (ANS) which were homologous with the genes reported in Arabidopsis) were analyzed by qRT-PCR (Fig. 1)
Summary
The anthocyanins are highly enriched in eggplants (Solanum melongena L.) with purple peel. Transcriptome study was made to explore the underlying molecular mechanisms of light-induced anthocyanin biosynthesis in eggplant (Solanum melongena L.) before color becomes evident. Anthocyanins are synthesized from phenylalanine, and under the continuous catalytic by phenylalanine ammonia lyase (PAL), 4-coumarate-CoA ligase (4CL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxyl enzyme (F3H), dihydroflavonol reductase (DFR) and anthocyanin synthase (ANS) or leucoanthocyanidin dioxygenase (LDOX). This pathway creates unstable anthocyanins [2] that are stabilized by glycosylation (GT), methylation (MT) or acylation (AT) before transportation to the cell vacuole for storage [3]. The structural anthocyanin biosynthesis genes of many plant species have been identified and are mostly polygenes, such as PAL, CHI, CHS, and DFR [5,6,7]
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