Xylan is a major acetylated polymer in plant lignocellulosic biomass and it can be mono- and di-acetylated at O-2 and O-3 as well as mono-acetylated at O-3 of xylosyl residues that is substituted with glucuronic acid (GlcA) at O-2. Based on the finding that ESK1, an Arabidopsis thaliana DUF231 protein, specifically mediates xylan 2-O- and 3-O-monoacetylation, we previously proposed that different acetyltransferase activities are required for regiospecific acetyl substitutions of xylan. Here, we demonstrate the functional roles of TBL32 and TBL33, two ESK1 close homologs, in acetyl substitutions of xylan. Simultaneous mutations of TBL32 and TBL33 resulted in a significant reduction in xylan acetyl content and endoxylanase digestion of the mutant xylan released GlcA-substituted xylooligomers without acetyl groups. Structural analysis of xylan revealed that the tbl32 tbl33 mutant had a nearly complete loss of 3-O-acetylated, 2-O-GlcA-substituted xylosyl residues. A reduction in 3-O-monoacetylated and 2,3-di-O-acetylated xylosyl residues was also observed. Simultaneous mutations of TBL32, TBL33 and ESK1 resulted in a severe reduction in xylan acetyl level down to 15% of that of the wild type, and concomitantly, severely collapsed vessels and stunted plant growth. In particular, the S2 layer of secondary walls in xylem vessels of tbl33 esk1 and tbl32 tbl33 esk1 exhibited an altered structure, indicating abnormal assembly of secondary wall polymers. These results demonstrate that TBL32 and TBL33 play an important role in xylan acetylation and normal deposition of secondary walls.
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A new monoterpene glycoside named paeonivayin with other seven known compounds were isolated from the roots of Paeonia delavayi Franch. and their structures were determined by means of spectroscopic studies.
monoterpene glycoside, Paeonia delavayi Franch, paeoniaceae, paeonivayin
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Objective: To study the components in the root of Pedicula dicora. Methods: Column chromatography with silica gel and polyamide was employed for the isolation and purification of ingredients. The structures were elucidated by spectral method. Result: Three iridoid glycosides were obtained and elucidated as mussaenoside, shanzhiside methyl ester and lamalbid. Conclusion: All the three compounds were separated from P. dicora for the first time.
iridoid glycoside, lamalbid, mussaenoside, Pedicula dicora, shanzhiside methyl ester
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In this paper, we present evidence that Ginsenoside-Rs(3) (G-Rs3), a new diol-type ginseng saponin isolated from the roots of Panax ginseng C.A. Meyer, efficiently arrests the cell cycle at the G1/S boundary at lower doses, 0.1-5 μM, but induces apoptosis at higher doses, 10-25 μM, the effects of which were associated with selectively elevating protein levels of p53 and p21(WAF1) in SK-HEP-1 cells. The cell growth suppressive and apoptosis inducing effects were confirmed by MTT assays together with flow cytometric analyses, morphological changes and DNA fragmentation. Immunoblotting showed that G-Rrs3 significantly elevated protein levels of p53 and p21(WAF1) prior to inducing apoptosis, while it did not elevate those of cyclin E, cyclin A, p27(Kip1), and PCNA. Immune complex kinase assays showed that G-Rs3 downregulated the activities of both cyclins E- and A-associated kinases. Collectively, we suggest that G-Rs3 selectively elevates protein levels of p53 and p21 and hence downregulates the activities of the cyclin-dependent kinases, resulting in cell cycle nn est at the G1/S boundary. We also propose that apoptosis induced by G-Rs3 is related to the elevations of p53 and p21(WAF1) in the cells.
apoptosis, p53, ginsenoside-Rs(3), p21(WAF1), SK-HEP-1 cells
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