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Biochemical and transcriptomic analyses reveal different metabolite biosynthesis profiles among three color and developmental stages in ‘ Anji Baicha ’ ( Camellia sinensis )

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ABSTRACT

Background: The new shoots of the albino tea cultivar ‘Anji Baicha’ are yellow or white at low temperatures and turn green as the environmental temperatures increase during the early spring. ‘Anji Baicha’ metabolite profiles exhibit considerable variability over three color and developmental stages, especially regarding the carotenoid, chlorophyll, and theanine concentrations. Previous studies focused on physiological characteristics, gene expression differences, and variations in metabolite abundances in albino tea plant leaves at specific growth stages. However, the molecular mechanisms regulating metabolite biosynthesis in various color and developmental stages in albino tea leaves have not been fully characterized.

Results: We used RNA-sequencing to analyze ‘Anji Baicha’ leaves at the yellow-green, albescent, and re-greening stages. The leaf transcriptomes differed considerably among the three stages. Functional classifications based on Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that differentially expressed unigenes were mainly related to metabolic pathways, biosynthesis of secondary metabolites, phenylpropanoid biosynthesis, and carbon fixation in photosynthetic organisms. Chemical analyses revealed higher β-carotene and theanine levels, but lower chlorophyll a levels, in the albescent stage than in the green stage. Furthermore, unigenes involved in carotenoid, chlorophyll, and theanine biosyntheses were identified, and the expression patterns of the differentially expressed unigenes in these biosynthesis pathways were characterized. Through co-expression analyses, we identified the key genes in these pathways. These genes may be responsible for the metabolite biosynthesis differences among the different leaf color and developmental stages of ‘Anji Baicha’ tea plants.

Conclusions: Our study presents the results of transcriptomic and biochemical analyses of ‘Anji Baicha’ tea plants at various stages. The distinct transcriptome profiles for each color and developmental stage enabled us to identify changes to biosynthesis pathways and revealed the contributions of such variations to the albino phenotype of tea plants. Furthermore, comparisons of the transcriptomes and related metabolites helped clarify the molecular regulatory mechanisms underlying the secondary metabolic pathways in different stages.

Electronic supplementary material: The online version of this article (doi:10.1186/s12870-016-0885-2) contains supplementary material, which is available to authorized users.

No MeSH data available.


Carotenoid concentrations and carotenoid biosynthesis unigenes at different stages. a The concentrations of β-carotene, lycopene, and lutein were determined at different stages. The asterisk indicates a significant difference between the YG or W stages and the G stage (P < 0.05; Student’s t-test). b Carotenoid biosynthesis pathway. The bracketed numbers in red following each gene name indicate the number of corresponding unigenes identified in our database. c All differentially expressed genes involved in carotenoid biosynthesis were hierarchically clustered and mapped using the fragments per kilobase of exon per million mapped reads values. Colors indicate the normalized signal intensity as defined in the bar
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Fig4: Carotenoid concentrations and carotenoid biosynthesis unigenes at different stages. a The concentrations of β-carotene, lycopene, and lutein were determined at different stages. The asterisk indicates a significant difference between the YG or W stages and the G stage (P < 0.05; Student’s t-test). b Carotenoid biosynthesis pathway. The bracketed numbers in red following each gene name indicate the number of corresponding unigenes identified in our database. c All differentially expressed genes involved in carotenoid biosynthesis were hierarchically clustered and mapped using the fragments per kilobase of exon per million mapped reads values. Colors indicate the normalized signal intensity as defined in the bar

Mentions: Carotenoids play vital roles during photosynthesis [24] and serve as precursors to abscisic acid [25, 26]. In tea plants, carotenoids are present as yellow pigments in fresh leaves and degrade into flavored terpenoids during the production of black tea [27]. Gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) analyses were conducted to determine the concentrations of β-carotene, lycopene, and lutein at different stages. Compared with the levels during the G stage, significantly higher β-carotene concentrations were observed in the W stage, while a significantly lower lutein concentration was detected in the YG stage (Fig. 4a). The β-carotene, lycopene, and lutein concentration trends differed considerably between the YG and G stages. The β-carotene concentration increased from the YG stage to the W stage, and then decreased from the W stage to the G stage. However, the lycopene and lutein concentrations increased from the YG stage to the G stage (Fig. 4a). Changes in carotenoid abundance are related to altered expression of carotenoid biosynthesis genes [28, 29]. In our database, 51 unigenes were annotated as key genes encoding enzymes related to carotenoid biosynthesis (Fig. 4b and Additional file 3). The expression profiles of all DEGs implicated in carotenoid biosynthesis were hierarchically clustered and plotted in a heat map (Fig. 4c).Fig. 4


Biochemical and transcriptomic analyses reveal different metabolite biosynthesis profiles among three color and developmental stages in ‘ Anji Baicha ’ ( Camellia sinensis )
Carotenoid concentrations and carotenoid biosynthesis unigenes at different stages. a The concentrations of β-carotene, lycopene, and lutein were determined at different stages. The asterisk indicates a significant difference between the YG or W stages and the G stage (P < 0.05; Student’s t-test). b Carotenoid biosynthesis pathway. The bracketed numbers in red following each gene name indicate the number of corresponding unigenes identified in our database. c All differentially expressed genes involved in carotenoid biosynthesis were hierarchically clustered and mapped using the fragments per kilobase of exon per million mapped reads values. Colors indicate the normalized signal intensity as defined in the bar
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
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getmorefigures.php?uid=PMC5015330&req=5

Fig4: Carotenoid concentrations and carotenoid biosynthesis unigenes at different stages. a The concentrations of β-carotene, lycopene, and lutein were determined at different stages. The asterisk indicates a significant difference between the YG or W stages and the G stage (P < 0.05; Student’s t-test). b Carotenoid biosynthesis pathway. The bracketed numbers in red following each gene name indicate the number of corresponding unigenes identified in our database. c All differentially expressed genes involved in carotenoid biosynthesis were hierarchically clustered and mapped using the fragments per kilobase of exon per million mapped reads values. Colors indicate the normalized signal intensity as defined in the bar
Mentions: Carotenoids play vital roles during photosynthesis [24] and serve as precursors to abscisic acid [25, 26]. In tea plants, carotenoids are present as yellow pigments in fresh leaves and degrade into flavored terpenoids during the production of black tea [27]. Gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) analyses were conducted to determine the concentrations of β-carotene, lycopene, and lutein at different stages. Compared with the levels during the G stage, significantly higher β-carotene concentrations were observed in the W stage, while a significantly lower lutein concentration was detected in the YG stage (Fig. 4a). The β-carotene, lycopene, and lutein concentration trends differed considerably between the YG and G stages. The β-carotene concentration increased from the YG stage to the W stage, and then decreased from the W stage to the G stage. However, the lycopene and lutein concentrations increased from the YG stage to the G stage (Fig. 4a). Changes in carotenoid abundance are related to altered expression of carotenoid biosynthesis genes [28, 29]. In our database, 51 unigenes were annotated as key genes encoding enzymes related to carotenoid biosynthesis (Fig. 4b and Additional file 3). The expression profiles of all DEGs implicated in carotenoid biosynthesis were hierarchically clustered and plotted in a heat map (Fig. 4c).Fig. 4

View Article: PubMed Central - PubMed

ABSTRACT

Background: The new shoots of the albino tea cultivar &lsquo;Anji Baicha&rsquo; are yellow or white at low temperatures and turn green as the environmental temperatures increase during the early spring. &lsquo;Anji Baicha&rsquo; metabolite profiles exhibit considerable variability over three color and developmental stages, especially regarding the carotenoid, chlorophyll, and theanine concentrations. Previous studies focused on physiological characteristics, gene expression differences, and variations in metabolite abundances in albino tea plant leaves at specific growth stages. However, the molecular mechanisms regulating metabolite biosynthesis in various color and developmental stages in albino tea leaves have not been fully characterized.

Results: We used RNA-sequencing to analyze &lsquo;Anji Baicha&rsquo; leaves at the yellow-green, albescent, and re-greening stages. The leaf transcriptomes differed considerably among the three stages. Functional classifications based on Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that differentially expressed unigenes were mainly related to metabolic pathways, biosynthesis of secondary metabolites, phenylpropanoid biosynthesis, and carbon fixation in photosynthetic organisms. Chemical analyses revealed higher &beta;-carotene and theanine levels, but lower chlorophyll a levels, in the albescent stage than in the green stage. Furthermore, unigenes involved in carotenoid, chlorophyll, and theanine biosyntheses were identified, and the expression patterns of the differentially expressed unigenes in these biosynthesis pathways were characterized. Through co-expression analyses, we identified the key genes in these pathways. These genes may be responsible for the metabolite biosynthesis differences among the different leaf color and developmental stages of &lsquo;Anji Baicha&rsquo; tea plants.

Conclusions: Our study presents the results of transcriptomic and biochemical analyses of &lsquo;Anji Baicha&rsquo; tea plants at various stages. The distinct transcriptome profiles for each color and developmental stage enabled us to identify changes to biosynthesis pathways and revealed the contributions of such variations to the albino phenotype of tea plants. Furthermore, comparisons of the transcriptomes and related metabolites helped clarify the molecular regulatory mechanisms underlying the secondary metabolic pathways in different stages.

Electronic supplementary material: The online version of this article (doi:10.1186/s12870-016-0885-2) contains supplementary material, which is available to authorized users.

No MeSH data available.