RESUMEN
Flavonol glycosides are associated with astringency and bitterness of teas. To clarify the dominant enzymatic reaction of flavonol glycosides in tea leaves, the catalytic effects of polyphenol oxidase (PPO), peroxidase (POD) and ß-glucosidase were studied, with the maintaining rates of total flavonol glycosides (TFG) being 73.0%, 99.8% and 94.3%. PPO was selected for further investigations, including the effects of pH value (3.5 ~ 6.5), temperature (25 °C ~ 55 °C) and dosage (39 ~ 72 U/mL PPO and 36 U/mL PPO, 3 ~ 36 U/mL POD). The oxidation of flavonol glycosides were intensified at pH 6.5, with 51.8% and 15.4% of TFG maintained after PPO and PPO + POD treatments, suggesting an enhancement from POD. The sensitivity ranking to PPO was: myricetin glycosides > quercetin glycosides > kaempferol glycosides. The inhibitor treatment testified the leading role of PPO in catalyzing flavonol glycosides in tea leaves. Sugar moiety enhanced the docking affinity of flavonol glycosides for PPO. PPO shows the potential of modifying flavonol glycoside composition.
Asunto(s)
Camellia sinensis/metabolismo , Catecol Oxidasa/metabolismo , Flavonoles/metabolismo , Hojas de la Planta/metabolismo , Camellia sinensis/química , Catecol Oxidasa/química , Flavonoides/química , Flavonoides/metabolismo , Flavonoles/química , Glicósidos/química , Concentración de Iones de Hidrógeno , Quempferoles/química , Quempferoles/metabolismo , Oxidación-Reducción , Peroxidasa/química , Peroxidasa/metabolismo , Extractos Vegetales/química , Extractos Vegetales/metabolismo , Hojas de la Planta/química , Té/química , Temperatura , beta-Glucosidasa/química , beta-Glucosidasa/metabolismoRESUMEN
Anthracnose is a major leaf disease in tea plant induced by Colletotrichum, which has led to substantial losses in yield and quality of tea. The molecular mechanism with regards to responses or resistance to anthracnose in tea remains unclear. A de novo transcriptome assembly dataset was generated from healthy and anthracnose-infected leaves on tea cultivars "Longjing-43" (LJ43) and "Zhenong-139" (ZN139), with 381.52 million pair-end reads, encompassing 47.78 billion bases. The unigenes were annotated versus Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), National Center for Biotechnology Information (NCBI) non-redundant protein sequences (Nr), evolutionary genealogy of genes: Non-supervised Orthologous Groups (eggNOG) and Swiss-prot. The number of differential expression genes (DEGs) detected between healthy and infected leaves was 1621 in LJ43 and 3089 in ZN139. The GO and KEGG enrichment analysis revealed that the DEGs were highly enriched in catalytic activity, oxidation-reduction, cell-wall reinforcement, plant hormone signal transduction and plant-pathogen interaction. Further studies by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and high-performance liquid chromatography (HPLC) showed that expression of genes involved in endogenous salicylic acid biosynthesis and also accumulation of foliar salicylic acid are involved in the response of tea plant to anthracnose infection. This study firstly provided novel insight in salicylic acid acting as a key compound in the responses of tea plant to anthracnose disease. The transcriptome dataset in this study will facilitate to profile gene expression and metabolic networks associated with tea plant immunity against anthracnose.