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Summary: Grass lignocelluloses feature complex compositions and structures. In addition to the presence of conventional lignin units from monolignols, acylated monolignols and flavonoid tricin also incorporate into lignin polymer; moreover, hydroxycinnamates, particularly ferulate, cross‐link arabinoxylan chains with each other and/or with lignin polymers. These structural complexities make grass lignocellulosics difficult to optimize for effective agro‐industrial applications. In the present study, we assess the applications of two engineered monolignol 4‐O‐methyltransferases (MOMTs) in modifying rice lignocellulosic properties. Two MOMTs confer regiospecific para‐methylation of monolignols but with different catalytic preferences. The expression of MOMTs in rice resulted in differential but drastic suppression of lignin deposition, showing more than 50% decrease in guaiacyl lignin and up to an 90% reduction in syringyl lignin in transgenic lines. Moreover, the levels of arabinoxylan‐bound ferulate were reduced by up to 50%, and the levels of tricin in lignin fraction were also substantially reduced. Concomitantly, up to 11 μmol/g of the methanol‐extractable 4‐O‐methylated ferulic acid and 5–7 μmol/g 4‐O‐methylated sinapic acid were accumulated in MOMT transgenic lines. Both MOMTs in vitro displayed discernible substrate promiscuity towards a range of phenolics in addition to the dominant substrate monolignols, which partially explains their broad effects on grass phenolic biosynthesis. The cell wall structural and compositional changes resulted in up to 30% increase in saccharification yield of the de‐starched rice straw biomass after diluted acid‐pretreatment. These results demonstrate an effective strategy to tailor complex grass cell walls to generate improved cellulosic feedstocks for the fermentable sugar‐based production of biofuel and bio‐chemicals. [ABSTRACT FROM AUTHOR]

BACKGROUND: Tomato is one of the widely cultivated crops worldwide that is affected by several pests, such as fungi (Fusarium oxysoporum, Alternaria solani), bacteria (Pectobacterium carotovorum) and weeds (Cyperus iria L., Amaranthus spinosus). A growing interest has emerged for developing plant‐derived pesticidal compounds to counteract these pests. One attractive alternative is to use barnyard grass (Echinochloa crus‐galli), known to be widely resistant to synthetic herbicides, as a potential biopesticide compound source. RESULTS: Phytochemical screening of the crude extract showed that phenolic compounds were the most abundant component present in barnyard grass. The crude extract was evaluated for antifungal, antibacterial and herbicidal activities. Bioassays showed inhibition against F. oxysporum (10.73 ± 1.30%) and A. solani (20.47 ± 3.51%), the causative agent of Fusarium rot and early blight disease in tomato, respectively. Antibacterial activity against P. carotovorum gave a mean zone of inhibition (paper disc diffusion assay) of 17.00 ± 1.00 mm and an IC50 (dose–response assay) of 2.26 mg mL−1 was observed. Dose–responsive herbicidal activity on the lettuce seed germination bioassay produced an IC50 of 459.30 ppm. Selectivity studies showed inhibition towards C. iria and A. spinosus with no effect on tomato. Lastly, bioassay‐guided fractionation coupled with untargeted metabolomics studies using ultra‐performance liquid chromatography with diode array detection–tandem mass spectrometry mass analyses revealed loliolide and tricin as the putative metabolites present in barnyard grass. CONCLUSION: To date, this is the first reported study on using barnyard grass as a potential alternative biopesticide against tomato pests such as fungi, bacteria and weeds. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Summary: Breeding approaches to enrich lignins in biomass could be beneficial to improving the biorefinery process because lignins increase biomass heating value and represent a potent source of valuable aromatic chemicals. However, despite the fact that grasses are promising lignocellulose feedstocks, limited information is yet available for molecular‐breeding approaches to upregulate lignin biosynthesis in grass species. In this study, we generated lignin‐enriched transgenic rice (Oryza sativa), a model grass species, via targeted mutagenesis of the transcriptional repressor OsMYB108 using CRISPR/Cas9‐mediated genome editing. The OsMYB108‐knockout rice mutants displayed increased expressions of lignin biosynthetic genes and enhanced lignin deposition in culm cell walls. Chemical and two‐dimensional nuclear magnetic resonance (NMR) analyses revealed that the mutant cell walls were preferentially enriched in γ‐p‐coumaroylated and tricin lignin units, both of which are typical and unique components in grass lignins. NMR analysis also showed that the relative abundances of major lignin linkage types were altered in the OsMYB108 mutants. Significance Statement: Comprehensive understanding of secondary cell wall formation in grasses, as major biomass feedstocks, is important for their molecular‐breeding applications toward improved biorefinery processes. We demonstrated that CRISPR/Cas9‐mediated mutagenesis of the transcriptional repressor gene OsMYB108 preferentially enriched grass‐specific lignin units, i.e. p‐coumaroylated units and tricin units, in rice (Oryza sativa), providing insight into the transcriptional regulatory network in secondary cell wall formation specific to grass species. [ABSTRACT FROM AUTHOR]

ABSTRACT: Treatment of human embryonic lung fibroblast (HEL) cells with tricin (4′, 5, 7‐trihydroxy‐3′, 5′‐dimethoxyflavone) following infection with human cytomegalovirus (HCMV) reportedly significantly suppresses HCMV replication. In the present work, the mechanisms for the anti‐HCMV effects of tricin in HEL cells were examined. It was found that exposure of HEL cells to tricin inhibited HCMV replication, with concomitant decreases in amounts of transcripts of the CC chemokine RANTES (CCL5)‐encoding gene and in expression of the CCL5 protein. It was also found that transcripts of HCMV immediate early 1 (IE1), and HCMV UL54 (encoding DNA polymerase) and replication of HCMV was significantly lower in CCL5 gene‐knockdown cells. These results suggest that the anti‐HCMV activity of tricin differs from that of ganciclovir and that CCL5 is one of the chemokines involved in HCMV replication. In addition, it is possible that chemokine CCL5 is one of the targets of tricin. [ABSTRACT FROM AUTHOR]

4′,5,7‐trihydroxy‐3′,5′‐dimethoxyflavone (tricin), derived from Sasa albo‐marginata, has been reported to suppress significantly human cytomegalovirus (HCMV) replication in human embryonic lung (HEL) fibroblast cells. However, the target protein of tricin remains unclear. This study focused on the anti‐HCMV activity of tricin in terms of its binding affinity to cyclin‐dependent kinase 9 (CDK9). A molecular docking study predicted that tricin binds well to the ATP‐binding site of CDK9. Experimental measurements then revealed that tricin inhibits the kinase activity of CDK9 and affects the phosphorylation of the carboxy‐terminal domain of RNA polymerase II. Based on these results, we conclude that CDK9 is one of the target proteins of tricin. We also found that tricin possesses anti‐HCMV activity with no cytotoxicity against HEL cells. [ABSTRACT FROM AUTHOR]

Defatted rice bran (DRB) is the byproduct of rice bran oil extraction. On HPLC analysis, methanolic extracts prepared from DRB was found to contain oryzanols (OYL), tocols and ferulic acid (FA). Solvent fractionation was employed to prepare extracts enriched with beneficial phytochemicals from crude methanolic extract (CME). The antioxidant potential of DRB extracts and their phytochemical constituents in emulsified media were evaluated by linoleic acid emulsion system and β-carotene bleaching test. In linoleic acid model, the activity indexed as percent inhibition values followed the order TBHQ (83.9) > BHT (60.1) > AE-PP = AE-LP = OYL = tricin (51.7) > Tmix (48.0) > FA (44.1) > AE (36.0) > CME (29.9) > sterol (22.8) with inhibition percentages at 200 ppm levels given in parentheses. The order for the β-carotene model was TBHQ (75.2) > BHT (54.1) > OYL = tricin = AE-LP = AE-PP (47.2) > Tmix (43.9) > FA (41.0) > AE (29.9) > CME (25.1) > sterol (20.1), with inhibition percentages at 200 ppm levels given in parentheses. The results demonstrated that DRB extracts could be used as antioxidant substitutes in heterogeneous food matrix and could also be used in protecting both linoleic acid and β-carotene against oxidation. The increase in activity with purification might be due to enhanced levels of antioxidants in purified extracts as compared to CME. [ABSTRACT FROM AUTHOR]