Abstract
BackgroundMethyl jasmonate (MeJA) has been successfully used as an effective elicitor to enhance production of taxol and other taxanes in cultured Taxus cells. However the mechanism of MeJA-mediated taxane biosynthesis remains unclear. Genomic information for species in the genus Taxus is currently unavailable. Therefore, information about the transcriptome of Taxus cells and specifically, description of changes in gene expression in response to MeJA, is needed for the better exploration of the biological mechanisms of MeJA-mediated taxane biosynthesis.ResultsIn this research, the transcriptome profiles of T. chinensis cells at 16 hours (T16) after MeJA treatment and of mock-treated cells (T0) were analyzed by “RNA-seq” to investigate the transcriptional alterations of Taxus cell in response to MeJA elicitation. More than 58 million reads (200 bp in length) of cDNA from both samples were generated, and 46,581 unigenes were found. There were 13,469 genes found to be expressed differentially between the two timepoints, including all of the known jasmonate (JA) biosynthesis/JA signaling pathway genes and taxol-related genes. The qRT-PCR results showed that the expression profiles of 12 randomly selected DEGs and 10 taxol biosynthesis genes were found to be consistent with the RNA-Seq data. MeJA appeared to stimulate a large number of genes involved in several relevant functional categories, such as plant hormone biosynthesis and phenylpropanoid biosynthesis. Additionally, many genes encoding transcription factors were shown to respond to MeJA elicitation.ConclusionsThe results of a transcriptome analysis suggest that exogenous application of MeJA could induce JA biosynthesis/JA signaling pathway/defence responses, activate a series of transcription factors, as well as increase expression of genes in the terpenoid biosynthesis pathway responsible for taxol synthesis. This comprehensive description of gene expression information could greatly facilitate our understanding of the molecular mechanisms of MeJA-mediated taxane biosynthesis in Taxus cells.
Highlights
Methyl jasmonate (MeJA) has been successfully used as an effective elicitor to enhance production of taxol and other taxanes in cultured Taxus cells
The contigs further assembled with paired-end joining and gap-filling to produce 61,703 scaffolds with an N50 of 839 bp (7,607 of which larger than 1,000 bp) for T0 and 60,601 scaffolds with an N50 of 812 bp (7,101 of which larger than 1,000 bp) for T16 (Table 1, Additional file 2). These scaffolds were respectively clustered with TGICL software [19] to generate 39,176 unigenes for T0 and 38,713 for T16, totalling 46,581 assembled unigenes (Table 1). These results indicate that the assembly and contig joining succeeded in processing a large amount of short reads from T. chinensis cell samples with relatively little redundancy
The two cell lines (T0, T16) were analyzed by Kyoto Encyclopedia of Genes and Genomes (KEGG), we found that the proteasome, Vibrio cholerae infection and cytosolic DNA-sensing pathway had the most significant changes (Additional file 9). 3,391 differentially expressed genes (DEGs) were annotated by KEGG, and this annotation revealed significant enrichment for genes found in metabolic pathways (806 DEGs, 23.77%), biosynthesis of plant hormones (226 DEGs, 6.66%), and biosynthesis of phenylpropanoids (204 DEGs, 6.02%) (Additional file 10)
Summary
Methyl jasmonate (MeJA) has been successfully used as an effective elicitor to enhance production of taxol and other taxanes in cultured Taxus cells. Information about the transcriptome of Taxus cells and description of changes in gene expression in response to MeJA, is needed for the better exploration of the biological mechanisms of MeJA-mediated taxane biosynthesis. Cultured Taxus cells as a renewable and sustainable system are a promising production route for taxol and protein CrMYC2’s regulation of ORCA gene expression, and the AP2/ERF-domain transcription factors ORCA2 and ORCA3, which in turn regulate a series of terpenoid indole alkaloids biosynthesis genes [6,10]. Though some mechanisms of the JA-elicited biosynthesis of secondary metabolites have been elucidated, the detailed biological mechanism of MeJA stimulation of taxane production and concomitant transcriptome changes associated with response to MeJA remain poorly understood. Recent research has demonstrated that RNA-Seq is well-suited for surveying the complexity of transcription, and for discovering genes and comparing gene expression profiles in eukaryotes [13,14,15,16,17,18]
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