Transcriptomic analyses identify albino-associated genes of a novel albino tea germplasm 'Huabai 1'

Abstract

Albinism in shoots of tea plants is a common phenotypic expression which gives the tea infusion a pleasant umami taste. A novel natural albino mutant tea germplasm containing high amino acids content was found and named as 'Huabai 1'. 'Huabai 1' has white jade tender shoots under low temperature and turns green with increased temperature. In order to understand the molecular mechanism of color change in leaf of 'Huabai 1', transcriptome analysis was performed to identify albino-associated differentially expressed genes (DEGs). A total of 483 DEGs were identified from white shoots of 'Huabai 1' compared to its green shoots. There were 15 DEGs identified to be involved in phenylpropanoid biosynthesis, which account for the majority of characterized DEGs. The metabolites related to phenylpropanoid biosynthesis revealed similar expression pattern of DEGs. Furthermore, metabolic pathways such as ubiquonone, tyrosine, and flavonoid biosynthesis associated with phenylpropanoid biosynthesis could also contribute to the color change in 'Huabai 1' tender shoots. Protein-protein interaction analysis revealed a hub protein NEDD8 (CSA009575) which interacted with many regulated genes in spliceosome, nitrogen metabolism, phenylpropanoid biosynthesis, and other pathways. In conclusion, the findings in this study indicate that the color change of 'Huabai 1' tender shoots is a combined effect of phenylpropanoid biosynthesis pathway and other metabolic pathways including flavonoid biosynthesis in tea plants. Chlorophyll biosynthesis-related genes LHCII and SGR may also play some roles in color change of 'Huabai 1'.

Fig. 1. The phenotype and chlorophyll content of white and green ‘Huabai 1’ leaves.

a leaf color of ‘Huabai 1’ new shoots. b Chlorophyll and carotenoid content of ‘Huabai 1’ new shoots; * represents significant difference

Fig. 2

Differentially expressed genes enriched on different KEGG pathways.

Fig. 3. Quantitative RT-PCR verification for randomly selected differentially expressed genes.

RNA-Seq and qRT-PCR data were displayed as fold changes

Fig. 4. The differentially expressed genes and metabolites on phenylpropanoid biosynthesis.

Red and green, respectively, mean up- and downregulation in white leaves compared to green leaves of ‘Huabai 1’

Fig. 5

Phenylpropanoid biosynthesis-associated metabolic pathways in responding to color change of ‘Huabai 1’.

Fig. 6. Protein–protein interaction network analysis based on the differentially expressed genes.

The definition and description of the proteins in this network are shown in Table S1

Fig. 7

The model of role of LHCII and SGR proteins on chlorophyll catalytic process.