Dataset Information

Relative expression of CsZCD gene and apocarotenoid biosynthesis during stigma development in Crocus sativus L.

ABSTRACT: Crocus sativus is a triploid sterile plant characterized by its red stigmas, which produce significant quantities of carotenoid derivatives formed from the oxidative cleavage of ?-carotene and zeaxanthin. The accumulation of three major carotenoid derivatives- crocin, picrocrocin, and safranal- is responsible for the color, bitter taste, and aroma of saffron, which is obtained from the dried stigma of Crocus. Maximum apocarotenoid accumulation occurs during fully developed scarlet stage of stigma development. Zeaxanthin is the precursor for biosynthesis of apocarotenoids. Crocus zeaxanthin 7, 8 (7, 8)-cleavage dioxygenase gene (CsZCD) encodes a chromoplast enzyme that initiates the biogenesis of these apocarotenoids by cleaving zeaxanthin. The Reverse Transcription-PCR analysis revealed that CsZCD gene expression followed different patterns during stigma development. Highest levels of CsZCD gene expression was observed in fully developed scarlet stage of stigma. Real Time PCR analysis showed that there is a sharp increase in gene expression from yellow to orange and orange to scarlet stages of stigma development. Increase in CsZCD gene expression parallels with the apocarotenoid content during the development of stigma, suggesting its regulatory role for apocarotenoid biosynthesis and stigma development in saffron.

SUBMITTER: Mir JI

PROVIDER: S-EPMC3550554 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

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Relative expression of CsZCD gene and apocarotenoid biosynthesis during stigma development in Crocus sativus L.

Mir J I JI Ahmed N N Wafai A H AH Qadri Raies A RA

Physiology and molecular biology of plants : an international journal of functional plant biology 20121001 4

Crocus sativus is a triploid sterile plant characterized by its red stigmas, which produce significant quantities of carotenoid derivatives formed from the oxidative cleavage of β-carotene and zeaxanthin. The accumulation of three major carotenoid derivatives- crocin, picrocrocin, and safranal- is responsible for the color, bitter taste, and aroma of saffron, which is obtained from the dried stigma of Crocus. Maximum apocarotenoid accumulation occurs during fully developed scarlet stage of stigm ...[more]

PMID: 24082500

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Project description:Crocus sativus stigmas form rich source of apocarotenoids like crocin, picrocrocin and saffranal which besides imparting color, flavour and aroma to saffron spice also have tremendous pharmacological properties. Inspite of their importance, the biosynthetic pathway of Crocus apocarotenoids is not fully elucidated. Moreover, the mechanism of their stigma specific accumulation remains unknown. Therefore, deep transcriptome sequencing of Crocus stigma and rest of the flower tissue was done to identify the genes and transcriptional regulators involved in the biosynthesis of these compounds.Transcriptome of stigma and rest of the flower tissue was sequenced using Illumina Genome Analyzer IIx platform which generated 64,604,402 flower and 51,350,714 stigma reads. Sequences were assembled de novo using trinity resulting in 64,438 transcripts which were classified into 32,204 unigenes comprising of 9853 clusters and 22,351 singletons. A comprehensive functional annotation and gene ontology (GO) analysis was carried out. 58.5 % of the transcripts showed similarity to sequences present in public databases while rest could be specific to Crocus. 5789 transcripts showed similarity to transcription factors representing 76 families out of which Myb family was most abundant. Many genes involved in carotenoid/apocarotenoid pathway were identified for the first time in this study which includes zeta-carotene isomerase and desaturase, carotenoid isomerase and lycopene epsilon-cyclase. GO analysis showed that the predominant classes in biological process category include metabolic process followed by cellular process and primary metabolic process. KEGG mapping analysis indicated that pathways involved in ribosome, carbon and starch and sucrose metabolism were highly represented. Differential expression analysis indicated that key carotenoid/apocarotenoid pathway genes including phytoene synthase, phytoene desaturase and carotenoid cleavage dioxygenase 2 are enriched in stigma thereby providing molecular proof for stigma to be the site of apocarotenoid biosynthesis.This data would provide a rich source for understanding the carotenoid/apocarotenoid metabolism in Crocus. The database would also help in investigating many questions related to saffron biology including flower development.

Project description:Saffron (Crocus sativus L.) is being embraced as the most important medicinal plant and the commercial source of saffron spice. Despite the beneficial economic and medicinal properties of saffron, the regulatory mechanism of the correlation of TFs and genes related to the biosynthesis of the apocarotenoids pathway is less obvious. Realizing these regulatory hierarchies of gene expression networks related to secondary metabolites production events is the main challenge owing to the complex and extensive interactions between the genetic behaviors. Recently, high throughput expression data have been highly feasible for constructing co-regulation networks to reveal the regulated processes and identifying novel candidate hub genes in response to complex processes of the biosynthesis of secondary metabolites. Herein, we performed Weighted Gene Co-expression Network Analysis (WGCNA), a systems biology method, to identify 11 regulated modules and hub TFs related to secondary metabolites. Three specialized modules were found in the apocarotenoids pathway. Several hub TFs were identified in notable modules, including MADS, C2H2, ERF, bZIP, HD-ZIP, and zinc finger protein MYB and HB, which were potentially associated with apocarotenoid biosynthesis. Furthermore, the expression levels of six hub TFs and six co-regulated genes of apocarotenoids were validated with RT-qPCR. The results confirmed that hub TFs specially MADS, C2H2, and ERF had a high correlation (P < 0.05) and a positive effect on genes under their control in apocarotenoid biosynthesis (CCD2, GLT2, and ADH) among different C. sativus ecotypes in which the metabolite contents were assayed. Promoter analysis of the co-expressed genes of the modules involved in apocarotenoids biosynthesis pathway suggested that not only are the genes co-expressed, but also share common regulatory motifs specially related to hub TFs of each module and that they may describe their common regulation. The result can be used to engineer valuable secondary metabolites of C. sativus by manipulating the hub regulatory TFs.

Dataset Information

Relative expression of CsZCD gene and apocarotenoid biosynthesis during stigma development in Crocus sativus L.

Publications

Relative expression of CsZCD gene and apocarotenoid biosynthesis during stigma development in Crocus sativus L.

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