Dataset Information

Isolation and functional characterization of a lycopene beta-cyclase gene that controls fruit colour of papaya (Carica papaya L.).

ABSTRACT: The colour of papaya fruit flesh is determined largely by the presence of carotenoid pigments. Red-fleshed papaya fruit contain lycopene, whilst this pigment is absent from yellow-fleshed fruit. The conversion of lycopene (red) to beta-carotene (yellow) is catalysed by lycopene beta-cyclase. This present study describes the cloning and functional characterization of two different genes encoding lycopene beta-cyclases (lcy-beta1 and lcy-beta2) from red (Tainung) and yellow (Hybrid 1B) papaya cultivars. A mutation in the lcy-beta2 gene, which inactivates enzyme activity, controls lycopene production in fruit and is responsible for the difference in carotenoid production between red and yellow-fleshed papaya fruit. The expression level of both lcy-beta1 and lcy-beta2 genes is similar and low in leaves, but lcy-beta2 expression increases markedly in ripe fruit. Isolation of the lcy-beta2 gene from papaya, that is preferentially expressed in fruit and is correlated with fruit colour, will facilitate marker-assisted breeding for fruit colour in papaya and should create possibilities for metabolic engineering of carotenoid production in papaya fruit to alter both colour and nutritional properties.

SUBMITTER: Devitt LC

PROVIDER: S-EPMC2791114 | biostudies-literature | 2010

REPOSITORIES: biostudies-literature

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Isolation and functional characterization of a lycopene beta-cyclase gene that controls fruit colour of papaya (Carica papaya L.).

Devitt Luke C LC Fanning Kent K Dietzgen Ralf G RG Holton Timothy A TA

Journal of experimental botany 20100101 1

The colour of papaya fruit flesh is determined largely by the presence of carotenoid pigments. Red-fleshed papaya fruit contain lycopene, whilst this pigment is absent from yellow-fleshed fruit. The conversion of lycopene (red) to beta-carotene (yellow) is catalysed by lycopene beta-cyclase. This present study describes the cloning and functional characterization of two different genes encoding lycopene beta-cyclases (lcy-beta1 and lcy-beta2) from red (Tainung) and yellow (Hybrid 1B) papaya cult ...[more]

PMID: 19887502

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Project description:BackgroundCarotenoids are a group of C40 isoprenoid molecules that play diverse biological and ecological roles in plants. Tomato is an important vegetable in human diet and provides the vitamin A precursor beta-carotene. Genes encoding enzymes involved in carotenoid biosynthetic pathway have been cloned. However, regulation of genes involved in carotenoid biosynthetic pathway and accumulation of specific carotenoid in chromoplasts are not well understood. One of the approaches to understand regulation of carotenoid metabolism is to characterize the promoters of genes encoding proteins involved in carotenoid metabolism. Lycopene beta-cyclase is one of the crucial enzymes in carotenoid biosynthesis pathway in plants. Its activity is required for synthesis of both alpha-and beta-carotenes that are further converted into other carotenoids such as lutein, zeaxanthin, etc. This study describes the isolation and characterization of chromoplast-specific Lycopene beta-cyclase (CYC-B) promoter from a green fruited S. habrochaites genotype EC520061.ResultsA 908 bp region upstream to the initiation codon of the Lycopene beta-cyclase gene was cloned and identified as full-length promoter. To identify promoter region necessary for regulating developmental expression of the ShCYC-B gene, the full-length promoter and its three different 5' truncated fragments were cloned upstream to the initiation codon of GUS reporter cDNA in binary vectors. These four plant transformation vectors were separately transformed in to Agrobacterium. Agrobacterium-mediated transient and stable expression systems were used to study the GUS expression driven by the full-length promoter and its 5' deletion fragments in tomato. The full-length promoter showed a basal level activity in leaves, and its expression was upregulated > 5-fold in flowers and fruits in transgenic tomato plants. Deletion of -908 to -577 bp 5' to ATG decreases the ShCYC-B promoter strength, while deletion of -908 to -437 bp 5' to ATG led to significant increase in the activity of GUS in the transgenic plants. Promoter deletion analysis led to the identification of a short promoter region (-436 bp to ATG) that exhibited a higher promoter strength but similar developmental expression pattern as compared with the full-length ShCYC-B promoter.ConclusionFunctional characterization of the full-length ShCYC-B promoter and its deletion fragments in transient expression system in fruto as well as in stable transgenic tomato revealed that the promoter is developmentally regulated and its expression is upregulated in chromoplast-rich flowers and fruits. Our study identified a short promoter region with functional activity and developmental expression pattern similar to that of the full-length ShCYC-B promoter. This 436 bp promoter region can be used in promoter::reporter fusion molecular genetic screens to identify mutants impaired in CYC-B expression, and thus can be a valuable tool in understanding carotenoid metabolism in tomato. Moreover, this short promoter region of ShCYC-B may be useful in genetic engineering of carotenoid content and other agronomic traits in tomato fruits.

Project description:BackgroundPapaya (Carica papaya) is an economically important fruit cultivated in the tropical and subtropical regions of China. However, the rapid softening rate after postharvest leads to a short shelf-life and considerable economic losses. Accordingly, understanding the mechanisms underlying fruit postharvest softening will be a reasonable way to maintain fruit quality and extend its shelf-life.ResultsMitogen-activated protein kinases (MAPKs) are conserved and play essential roles in response to biotic and abiotic stresses. However, the MAPK family remain poorly studied in papaya. Here, a total of nine putative CpMAPK members were identified within papaya genome, and a comprehensive genome-wide characterization of the CpMAPKs was performed, including evolutionary relationships, conserved domains, gene structures, chromosomal locations, cis-regulatory elements and expression profiles in response to phytohormone and antioxidant organic compound treatments during fruit postharvest ripening. Our findings showed that nearly all CpMAPKs harbored the conserved P-loop, C-loop and activation loop domains. Phylogenetic analysis showed that CpMAPK members could be categorized into four groups (A-D), with the members within the same groups displaying high similarity in protein domains and intron-exon organizations. Moreover, a number of cis-acting elements related to hormone signaling, circadian rhythm, or low-temperature stresses were identified in the promoters of CpMAPKs. Notably, gene expression profiles demonstrated that CpMAPKs exhibited various responses to 2-chloroethylphosphonic acid (ethephon), 1-methylcyclopropene (1-MCP) and the combined ascorbic acid (AsA) and chitosan (CTS) treatments during papaya postharvest ripening. Among them, both CpMAPK9 and CpMAPK20 displayed significant induction in papaya flesh by ethephon treatment, and were pronounced inhibition after AsA and CTS treatments at 16 d compared to those of natural ripening control, suggesting that they potentially involve in fruit postharvest ripening through ethylene signaling pathway or modulating cell wall metabolism.ConclusionThis study will provide some valuable insights into future functional characterization of CpMAPKs, and hold great potential for further understanding the molecular mechanisms underlying papaya fruit postharvest ripening.

Dataset Information

Isolation and functional characterization of a lycopene beta-cyclase gene that controls fruit colour of papaya (Carica papaya L.).

Publications

Isolation and functional characterization of a lycopene beta-cyclase gene that controls fruit colour of papaya (Carica papaya L.).

Similar Datasets

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