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Background Liver cancer is the second leading causes of cancer-related death globally. Pyrroline-5-carboxylate reductase 1 (PYCR1) plays a critical role in metabolic profiles of tumors. Therefore, it is necessary to explore the mechanisms of PYCR1 on cell growth and survival in hepatocellular carcinoma (HCC). Methods Protein and mRNA expression levels of PYCR1 in 140 pairs of tumor and adjacent normal liver tissues of HCC patients were analyzed by immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR). Expressions of PYCR1 were inhibited in BEL-7404 cells and SMMC-7721 cells using gene interference technology. The cell proliferation was detected by Celigo and MTT assay. The colony formation assay was also performed. The cell apoptosis was measured by flow cytometric assay. The effect of PYCR1 interference on tumor growth was observed by xenograft nude mice assay in vivo. The downstream pathway of PYCR1 interference was searched by microarray and bioinformatics analysis, and validated by qRT-PCR and western blot. Results PYCR1 levels were significantly up-regulated in HCC tumor tissues than adjacent normal liver tissues in both protein and mRNA levels (P < 0.01). In vitro, the cell proliferation was significantly slower in shPYCR1 group than shCtrl group in BEL-7404 and SMMC-7721 cells (P < 0.001). The colony number was significantly smaller after PYCR1 interference (P < 0.01). The percentage of apoptosis cells significantly increased in shPYCR1 group (P < 0.01). In vivo, PYCR1 interference could obviously suppress tumor growth in xenograft nude mice. The volume and weight of tumors were significantly smaller via PYCR1 interference. The c-Jun N-terminal kinase (JNK) signaling pathway significantly altered, and insulin receptor substrate 1 (IRS1) were significantly down-regulated by PYCR1 interference in both mRNA and protein levels (P < 0.001). Conclusion PYCR1 interference could inhibit cell proliferation and promote cell apoptosis in HCC through regluting JNK/IRS1 pathway. Our study will provide a drug target for HCC therapy and a potential biomarker for its diagnosis or prognosis.

Flavonol glycosides, which are often converted from aglycones in a process catalyzed by UDP-glycosyltransferases (UGTs), play an important role for the health of plants and animals. In the present study, a gene encoding a flavonoid 7-O-glycosyltransferase (CsUGT75L12) was identified in tea plants. Recombinant CsUGT75L12 protein displayed glycosyltransferase activity on the 7-OH position of multiple phenolic compounds. In relative comparison to wild-type seeds, the levels of flavonol-glucosides increased in Arabidopsis seeds overexpressing CsUGT75L12. In order to determine the key amino acid residues responsible for the catalytic activity of the protein, a series of site-directed mutagenesis and enzymatic assays were performed based on the 3D structural modeling and docking analyses. These results suggested that residue Q54 is a double binding site that functions as both a sugar receptor and donor. Residues H56 and T151, corresponding to the basic active residues H20 and D119 of VvGT1, were not irreplaceable for CsUGT75L12. In addition, residues Y182, S223, P238, T239, and F240 were demonstrated to be responsible for a ‘reversed’ sugar receptor binding model. The results of single and triple substitutions confirmed that the function of residues P238, T239, and F240 may substitute or compensate with each other for the flavonoid 7-O-glycosyltransferase activity.

Plant tannins, including condensed tannins (CTs) and hydrolyzable tannins (HTs), are widely distributed in the plant kingdom. To date, tannase (TA)is a type of tannin acyl-hydrolase hydrolyzing HTs, CT monomer gallates and depsideshas been reported in microbes only. Whether plants express TA remains unknown.Herein, we report plant TA genes. A native Camellia sinensis TA (CsTA) is identified from leaves. Six TAs are cloned from tea, strawberry (Fragaria 9 ananassa, Fa) and four other crops. Biochemical analysis shows that the native CsTA and six recombinant TAs hydrolyze tannin compounds, depsides and phenolic glycosides.Transcriptional and metabolic analyses reveal that the expression of CsTA is oppositely associated with the accumulation of galloylated catechins. Moreover, the transient overexpression and RNA interference of FaTA are positively associated with the accumulation of ellagitannins in strawberry fruit. Phylogenetic analysis across different kingdoms shows that 29 plant TA homologs are clustered as a plant-specific TA clade in class I carboxylesterases. Further analysis across the angiosperms reveals that these TA genes are dispersed in tanninrich plants, which share a single phylogenetic origin c. 120 million yr ago.Plant TA is discovered for the first time in the plant kingdom and is shown to be valuable to improve tannin compositions in plants.