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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.


‘Anji Baicha’ tea leaves and transcriptome profiles in different stages. a YG, yellow-green leaf; W, white leaf; G, re-greening leaf. Details for each tissue are described in the Methods section under “Plant materials”. b CummeRbund was used to analyze the leaf transcript level data from the three analyzed stages (three biological replicates). The RNA-sequencing samples clustered into three groups of three replicate samples according to these stages. These results indicated that the three biological replicates produced consistent gene expression data at each stage, and that the expression levels of unigenes in leaves differed among stages
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Fig1: ‘Anji Baicha’ tea leaves and transcriptome profiles in different stages. a YG, yellow-green leaf; W, white leaf; G, re-greening leaf. Details for each tissue are described in the Methods section under “Plant materials”. b CummeRbund was used to analyze the leaf transcript level data from the three analyzed stages (three biological replicates). The RNA-sequencing samples clustered into three groups of three replicate samples according to these stages. These results indicated that the three biological replicates produced consistent gene expression data at each stage, and that the expression levels of unigenes in leaves differed among stages

Mentions: In early spring, the color of ‘Anji Baicha’ new shoots is affected by environmental temperatures. At temperatures below 20 °C, new shoots are yellow-green or white. With increasing temperatures, new shoots gradually turn green. The albino phenotype is closely related to chlorophyll synthesis, which is inhibited at low temperatures and restored when the temperature increases [2]. The development of new shoots was divided into three stages based on differences in leaf color (Fig. 1a). The initial germination period, in which plants consisted of one yellow-green leaf and one bud, was defined as the yellow-green (YG) stage. During this stage, leaves were light green with a yellow edge. As the first leaf developed, it became off-white and only the leaf vein remained green. This period was defined as the albescent (W) stage. When temperatures increased above 22 °C, leaves grew larger and gradually turned green, similar to the leaves of other tea cultivars. This stage was defined as the re-greening (G) stage.Fig. 1


Biochemical and transcriptomic analyses reveal different metabolite biosynthesis profiles among three color and developmental stages in ‘ Anji Baicha ’ ( Camellia sinensis )
‘Anji Baicha’ tea leaves and transcriptome profiles in different stages. a YG, yellow-green leaf; W, white leaf; G, re-greening leaf. Details for each tissue are described in the Methods section under “Plant materials”. b CummeRbund was used to analyze the leaf transcript level data from the three analyzed stages (three biological replicates). The RNA-sequencing samples clustered into three groups of three replicate samples according to these stages. These results indicated that the three biological replicates produced consistent gene expression data at each stage, and that the expression levels of unigenes in leaves differed among stages
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig1: ‘Anji Baicha’ tea leaves and transcriptome profiles in different stages. a YG, yellow-green leaf; W, white leaf; G, re-greening leaf. Details for each tissue are described in the Methods section under “Plant materials”. b CummeRbund was used to analyze the leaf transcript level data from the three analyzed stages (three biological replicates). The RNA-sequencing samples clustered into three groups of three replicate samples according to these stages. These results indicated that the three biological replicates produced consistent gene expression data at each stage, and that the expression levels of unigenes in leaves differed among stages
Mentions: In early spring, the color of ‘Anji Baicha’ new shoots is affected by environmental temperatures. At temperatures below 20 °C, new shoots are yellow-green or white. With increasing temperatures, new shoots gradually turn green. The albino phenotype is closely related to chlorophyll synthesis, which is inhibited at low temperatures and restored when the temperature increases [2]. The development of new shoots was divided into three stages based on differences in leaf color (Fig. 1a). The initial germination period, in which plants consisted of one yellow-green leaf and one bud, was defined as the yellow-green (YG) stage. During this stage, leaves were light green with a yellow edge. As the first leaf developed, it became off-white and only the leaf vein remained green. This period was defined as the albescent (W) stage. When temperatures increased above 22 °C, leaves grew larger and gradually turned green, similar to the leaves of other tea cultivars. This stage was defined as the re-greening (G) stage.Fig. 1

View Article: PubMed Central - PubMed

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.