Integrated analyses of the transcriptome and metabolome of the leaves of albino tea cultivars reveal coordinated regulation of the carbon and nitrogen metabolism

Previous studies have revealed that dramatic changes in metabolism occur in albino tea leaves compared with regular green tea leaves. In particular, the flavonoid content decreased while the amino acid content increased notably, indicating that both the carbon and nitrogen metabolism had undergone significant changes. To understand the coordinated regulation of carbon and nitrogen metabolism in albino tea leaves, we performed integrated analyses of the metabolome and transcriptome for both the albino (baiye 1) tea plant and the regular (Longjing 43 as control) tea plant. Based on the multivariate statistics of principal component analysis and OPLS-DA (orthogonal partial least squares-discriminant analysis), leaves from the baiye 1 and Longjing 43 tea plants were classified into three developmental stages. By identifying the main biomarkers from the different groups and from pathway analysis, we gained new insight into understanding the mechanism of the carbon and nitrogen metabolism in the leaves of the albino mutant plants: the serious weakening of the carbon metabolism in the albino leaves led to a reduced nitrogen consumption. However, nitrogen catabolism was enhanced to generate/supply more carbon skeletons for energy metabolism, which helped to coordinate the dramatic changes in metabolism resulting from the carbon-deficiency stress in the albino leaves. Moreover, the reallocation of carbon and highly efficient recycling of endogenous ammonium also constituted a potential mechanism for regulating the balance of carbon and nitrogen metabolism in albino leaves under carbon-deficiency stress. All of these metabolic responses in albino leaves create a potential mechanism for regulating the balance of carbon and nitrogen metabolism under conditions of carbon deficiency. Moreover, the coordinated regulation of the carbon and nitrogen metabolism, including reallocation of carbon resource from secondary metabolites and amino acids, highly efficient way to recycle and store endogenous ammonium, plays a great role for the albino tea plant in surviving from the carbon deficiency stress.