Untargeted metabolomic analysis using UPLC-MS/MS identifies metabolites involved in shoot growth and development in pruned tea plants (Camellia sinensis (L.) O. Kuntz)

Pruning is a routine management practice in tea cultivation. Although pruning is speculated to contribute to shoot growth and development in tea plants, it is imperative to understand the molecular mechanism involved. In order to investigate this, tea plants were pruned at different levels. Analysis of shoot growth indices revealed significant increase in shoots number and weight in shoots of pruned tea plant. Auxin assay showed higher concentrations of indole-3-acetic acid in pruned samples. Metabolomic analysis identified 80 differential metabolites in shoots of pruned plants, of which indole-3-acetonitrile and menaquinone were the common metabolites in all levels of pruning. The metabolites are involved in auxin biosynthesis, as shown by protein-protein interaction analysis. The metabolites enriched major metabolic pathways such as tryptophan metabolism, vitamin digestion and absorption, biosynthesis of ubiquinone and other terpenoid-quinone, and biosynthesis of amino acids. 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. This study concludes that 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. This study contributes to knowledge in molecular mechanism of shoot growth and development.