Abstract：
Transcriptome analysis revealed that albinism in tea plant is a combined effect of phenylpropanoid biosynthesis and other metabolic pathways including ‘ubiquinone and tyrosine’ biosynthesis. Wide target metabolome analysis identified phenylpropanoid- associated metabolites as the dominant differential metabolites in shoots of ‘Huabai 1’; and lipids, and ‘nucleotide and its derivatives’ in ‘Baiye 1’. Most of the metabolites mapped to amino acid metabolism and enriched ‘flavone, flavonol and flavonoids’ biosynthesis on the KEGG pathway. To reveal the role of auxin and nitrogen in lateral roots formation and development, transcriptome analysis identified DEGs for cytokinin and ethylene biosynthesis, and four signaling pathways, namely nitrogen metabolism, plant hormone signal transduction, glutathione metabolism and transcription factors. Analysis of shoot growth indices in pruned plants revealed significant increase in shoot number and shoot weight. Auxin assay showed higher concentrations of indole-3-acetic acid in pruned samples. A total of 80 metabolites involved in various metabolic pathways such as phenylpropanoids biosynthesis, auxin biosynthesis, tryptophan metabolism, purine metabolism, vitamin digestion and absorption, biosynthesis of ubiquinone and other terpenoid-quinone, and biosynthesis of amino acids were identified in shoots of pruned plants. Genes involved in auxin signalling and menaquinone synthesis were up-regulated in pruned plants. This study reports, for the first time in nature, the synthesis of menaquinone in plants. Pruning enhances shoot growth and development through the modulation of indole-3-acetic acid via synthesis of indole-3-acetonitrile and menaquinone in shoots, a combined effect of tryptophan metabolism and other metabolic pathways. To investigated the metabolic alterations in lateral roots of pruned tea to unveil the mechanism of nutrients uptake, metabolic profiling showed significant metabolic variations in lateral roots of pruned tea. Flavonoid biosynthesis, phenylpropanoid biosynthesis, and amino acid metabolism were differentially regulated in lateral roots. Caffeine metabolism was significantly hindered and ethylene signaling was significantly induced in lateral roots of pruned plant. In addition, intermediates in the tricarboxylic acid cycle were up-regulated, indicating high rates of TCA cycle. Therefore, pathways related to phenylpropanoid biosynthesis, TCA cycle, ethylene biosynthesis and metabolism of amino acids contribute to higher nutrients uptake by lateral roots of tea plant. These studies contribute to the knowledge base in plant transcriptomics and metabolomics.
