Knockout of CAFFEOYL-COA 3-O-METHYLTRANSFERASE 6/6L enhances the S/G ratio of lignin monomers and disease resistance in Nicotiana tabacum

Overexpression of OsCCR1, OsCOMT5, OsCAD2 and OsCCoAOMT1 Genes Enhances Lignin Accumulation and Confers Tolerance Against Rhizoctonia solani in Rice (Oryza sativa)

The necrotrophic fungus, Rhizoctonia solani is the major cause of sheath blight, a disease that leads to a significant reduction in rice yield, posing a serious threat to food security. Traditional breeding approaches have struggled to develop effective resistance, highlighting the importance of transgenic technology as a promising solution. This study explored the relationship between enhanced lignin production and the overexpressing key lignin biosynthesis genes (OsCCR1, OsCOMT5, OsCAD2, and OsCCoAOMT1), demonstrating that increased lignin accumulation strengthens defense mechanisms against R. solani by preventing its penetration of the cell wall. Thioacidolysis analysis revealed higher lignin levels in the leaf sheath tissues of OX-OsCCR1 transgenic rice plants, which effectively blocked fungal hyphae invasion, as confirmed by confocal and scanning electron microscopy. Similarly, the cell walls of OX-OsCOMT5 transgenic lines accumulated significantly higher levels of cell wall-bound phenolics, which inhibited R. solani ingress and infection peg formation. Notably, OX-4C transgenic rice plants, overexpressing all four lignin biosynthesis genes, exhibited elevated levels of lignin in the leaf sheath during early infection, serving as a robust first line of defense. These findings underscore the critical role of cell wall restructuring, particularly through increased lignin deposition, in combating sheath blight infection and enhancing crop resilience. Engineering the lignin biosynthesis pathway provides a promising approach for developing broad-spectrum resistance to fungal pathogens in other economically important crops, paving the way for sustainable agriculture and food security.

Caffeic acid O-methyltransferase-dependent flavonoid defenses promote sorghum resistance to fall armyworm infestation

Sorghum (Sorghum bicolor), one of the world's most important monocot crops, suffers severe yield losses due to attack by a polyphagous insect pest, fall armyworm (FAW; Spodoptera frugiperda). Here, we show that the Brown midrib 12 (Bmr12) gene, which encodes the caffeic acid O-methyltransferase (COMT) enzyme, promotes sorghum defense against FAW. Loss of Bmr12 function resulted in increased susceptibility, but enhanced resistance to FAW was observed in Bmr12-overexpression (OE) plants compared with wild-type (RTx430) plants. Although COMT is associated with modulating lignin levels, FAW infestation resulted in comparable lignin levels between bmr12 and Bmr12-OE sorghum plants. On the contrary, evidence presented here indicates that FAW feeding induced the accumulation of flavonoids, which was previously shown to have a negative impact on FAW growth and survival in Bmr12-OE plants compared with bmr12 and RTx430 plants. Furthermore, a combination of phytohormone profiling and transcriptomic analysis uncovered that COMT-mediated resistance to FAW depends on jasmonic acid (JA) and oxidative stress-associated pathways. Exogenous application of FAW oral secretions stimulated flavonoid accumulation in Bmr12-OE plants compared with bmr12 and RTx430 plants, indicating that COMT has an essential function in perceiving FAW oral cues. Taken together, the critical role of COMT in sorghum defense against FAW hinges upon the interplay between JA and its derivatives and hydrogen peroxide, which potentially helps to mount a robust flavonoid-based host defense upon caterpillar attack.

Lignin lite: Boosting plant power through selective downregulation

This article explores the dual benefits of reducing lignin content in plants, which streamlines biofuel production while maintaining robust defence mechanisms. It discusses how plants compensate for lower lignin levels through alternative defence strategies, recent biotechnological advances in lignin modification, and the implications for agriculture and industry.

Integrated Transcriptome and Proteome Analysis Reveals the Regulatory Mechanism of Root Growth by Protein Disulfide Isomerase in Arabidopsis

Protein disulfide isomerase (PDI, EC 5.3.4.1) is a thiol-disulfide oxidoreductase that plays a crucial role in catalyzing the oxidation and rearrangement of disulfides in substrate proteins. In plants, PDI is primarily involved in regulating seed germination and development, facilitating the oxidative folding of storage proteins in the endosperm, and also contributing to the formation of pollen. However, the role of PDI in root growth has not been previously studied. This research investigated the impact of PDI gene deficiency in plants by using 16F16 [2-(2-Chloroacetyl)-2,3,4,9-tetrahydro-1-methyl-1H-pyrido[3,4-b]indole-1-carboxylic acid methyl ester], a small-molecule inhibitor of PDI, to remove functional redundancy. The results showed that the growth of Arabidopsis roots was significantly inhibited when treated with 16F16. To further investigate the effects of 16F16 treatment, we conducted expression profiling of treated roots using RNA sequencing and a Tandem Mass Tag (TMT)-based quantitative proteomics approach at both the transcriptomic and proteomic levels. Our analysis revealed 994 differentially expressed genes (DEGs) at the transcript level, which were predominantly enriched in pathways associated with "phenylpropane biosynthesis", "plant hormone signal transduction", "plant-pathogen interaction" and "starch and sucrose metabolism" pathways. Additionally, we identified 120 differentially expressed proteins (DEPs) at the protein level. These proteins were mainly enriched in pathways such as "phenylpropanoid biosynthesis", "photosynthesis", "biosynthesis of various plant secondary metabolites", and "biosynthesis of secondary metabolites" pathways. The comprehensive transcriptome and proteome analyses revealed a regulatory network for root shortening in Arabidopsis seedlings under 16F16 treatment, mainly involving phenylpropane biosynthesis and plant hormone signal transduction pathways. This study enhances our understanding of the significant role of PDIs in Arabidopsis root growth and provides insights into the regulatory mechanisms of root shortening following 16F16 treatment.