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. 2023 Sep 6:14:1219335.
doi: 10.3389/fgene.2023.1219335. eCollection 2023.

Insights into the physiological, molecular, and genetic regulators of albinism in Camellia sinensis leaves

Yang Zhao  1 , Peidi Yang  1 , Yang Cheng  1 , Yong Liu  1 , Yang Yang  1 , Zhen Liu  1
Affiliations

Insights into the physiological, molecular, and genetic regulators of albinism in Camellia sinensis leaves

Yang Zhao et al. Front Genet. .

Abstract

Introduction: Yanling Yinbiancha, a cultivar of Camellia sinensis (L.) O. Kuntze, is an evergreen woody perennial with characteristic albino leaves. A mutant variant with green leaves on branches has been recently identified. The molecular mechanisms underlying this color variation remain unknown. Methods: We aimed to utilize omics tools to decipher the molecular basis for this color variation, with the ultimate goal of enhancing existing germplasm and utilizing it in future breeding programs. Results and discussion: Albinotic leaves exhibited significant chloroplast degeneration and reduced carotenoid accumulation. Transcriptomic and metabolomic analysis of the two variants revealed 1,412 differentially expressed genes and 127 differentially accumulated metabolites (DAMs). Enrichment analysis for DEGs suggested significant enrichment of pathways involved in the biosynthesis of anthocyanins, porphyrin, chlorophyll, and carotenoids. To further narrow down the causal variation for albinotic leaves, we performed a conjoint analysis of metabolome and transcriptome and identified putative candidate genes responsible for albinism in C. sinensis leaves. 12, 7, and 28 DEGs were significantly associated with photosynthesis, porphyrin/chlorophyll metabolism, and flavonoid metabolism, respectively. Chlorophyllase 2, Chlorophyll a-Binding Protein 4A, Chlorophyll a-Binding Protein 24, Stay Green Regulator, Photosystem II Cytochrome b559 subunit beta along with transcription factors AP2, bZIP, MYB, and WRKY were identified as a potential regulator of albinism in Yanling Yinbiancha. Moreover, we identified Anthocyanidin reductase and Arabidopsis Response Regulator 1 as DEGs influencing flavonoid accumulation in albino leaves. Identification of genes related to albinism in C. sinensis may facilitate genetic modification or development of molecular markers, potentially enhancing cultivation efficiency and expanding the germplasm for utilization in breeding programs.

Keywords: albinism; carotenoids; chlorophyll; flavonoids; leaves; pigmentation.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Morpho-physiological description of C. sinensis (A) A visual representation of Camellia sinensis leaves is provided, wherein L1 and L2 denote the first and second leaves of the plant. The first and second leaves of the green branch are designated as G1 and G2, respectively, while the first and second leaves of the mutant branch are labeled as A1 and A2 (B) Chlorophyll and carotenoid determination in green and albino leaves. A represents the albino leaves and G represents green leaves. ** indicate highly significant differences (p < 0.01) and * represents significant differences (p < 0.05).
FIGURE 2
FIGURE 2
Overview of transcriptome and metabolome profile (A) DEGs identification (B) DAMs identification (C) DEGs characterization in upregulated and downregulated DEGs (D) DAMs characterization in up-accumulated and down-accumulated DAMs (E) Accumulation pattern of differentially accumulated metabolites and their classification.
FIGURE 3
FIGURE 3
GO enrichment analysis for differentially expressed genes (DEGs) in comparison of albino leaves with green leaves (A vs. G).
FIGURE 4
FIGURE 4
Characterization of identified DEGs and Transcription factors in green and albino leaves (A) DEGs identified in carotenoid biosynthesis, chlorophyll biosynthesis and stay green trait. G denotes to green leaves and A denotes to albino leaves, while 1, 2, and 3 are corresponding replicates. The regulation pattern depicting upregulation and downregulation in albino leaves compared to green leaves (A vs. G) (B) Expression profile of transcription factors identified as DEGs.
FIGURE 5
FIGURE 5
Characterization of flavonoid biosynthesis in green and albino leaves (A) DEGs identified in flavonoid biosynthesis. G denotes to green leaves and A denotes to albino leaves, while 1, 2, and 3 are corresponding replicates. The regulation pattern depicting upregulation and downregulation in albino leaves compared to green leaves (A vs. G) (B) Accumulation patterns of differentially accumulated metabolites (DAMs) in green and albino leaves. G denotes to green leaves and A denotes to albino leaves, while 1, 2, and 3 are corresponding replicates.
FIGURE 6
FIGURE 6
Conjoint analysis of transcriptome and metabolome (A) Nine-quadrant diagram of metabolite and transcriptome expression patterns (B) Correlation heatmap of metabolite and transcriptome expression patterns (C) KEGG pathways associated with co regulated DAMs and DEGs (D) correlation network of all the co-regulated DEGs and DAMs (E) correlation network of co-regulated DEGs and DAMs associated with flavonoid biosynthesis pathway (F) correlation network of co-regulated DEGs and DAMs associated with chlorophyll biosynthesis pathway.
FIGURE 7
FIGURE 7
qRT-PCR based expression analysis of selected genes (A) Relative expression profile of 17 selected genes based on qRT-PCR (B) Correlation estimates of RNA-seq quantitation and qRT-PCR results.
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