Cloning and characterization of the lignin biosynthesis genes NcCSE and NcHCT from Neolamarckia cadamba

Woody plant cell walls: Fundamentals and utilization

Cell walls in plants, particularly forest trees, are the major carbon sink of the terrestrial ecosystem. Chemical and biosynthetic features of plant cell walls were revealed early on, focusing mostly on herbaceous model species. Recent developments in genomics, transcriptomics, epigenomics, transgenesis, and associated analytical techniques are enabling novel insights into formation of woody cell walls. Here, we review multilevel regulation of cell wall biosynthesis in forest tree species. We highlight current approaches to engineering cell walls as potential feedstock for materials and energy and survey reported field tests of such engineered transgenic trees. We outline opportunities and challenges in future research to better understand cell type biogenesis for more efficient wood cell wall modification and utilization for biomaterials or for enhanced carbon capture and storage.

Lignin and Its Pathway-Associated Phytoalexins Modulate Plant Defense against Fungi

Fungi infections cause approximately 60-70% yield loss through diseases such as rice blast, powdery mildew, Fusarium rot, downy mildew, etc. Plants naturally respond to these infections by eliciting an array of protective metabolites to confer physical or chemical protection. Among plant metabolites, lignin, a phenolic compound, thickens the middle lamella and the secondary cell walls of plants to curtail fungi infection. The biosynthesis of monolignols (lignin monomers) is regulated by genes whose transcript abundance significantly improves plant defense against fungi. The catalytic activities of lignin biosynthetic enzymes also contribute to the accumulation of other defense compounds. Recent advances focus on modifying the lignin pathway to enhance plant growth and defense against pathogens. This review presents an overview of monolignol regulatory genes and their contributions to fungi immunity, as reported over the last five years. This review expands the frontiers in lignin pathway engineering to enhance plant defense.

Lignin biosynthesis regulated by CsCSE1 is required for Cucumis sativus defence to Podosphaera xanthii

Lignin is a complex phenolic compound that can enhance the stiffness, hydrophobicity, and antioxidant capacity of the cell wall; it thus provides a critical barrier against pathogen and insect invaders. Caffeoyl shikimate esterase (CSE) is a key novel enzyme involved in lignin biosynthesis that is associated with genetic improvements in lignocellulosic biomass; however, no research thus far have revealed the role of CSE in resistance to pathogenic stress. CsCSE1 (Cucsa.134370) has previously been shown to highly associated with the response of cucumber to attack by Podosphaera xanthii through RNA sequencing. Here, we detected the exactly role of CsCSE1 in the defence of cucumber to P. xanthii infection. Homologous sequence alignment revealed that CsCSE1 contains two highly conserved lyase domains (GXSXG), suggesting that CsCSE1 possesses CSE activity. Subcellular localization analysis manifested that CsCSE1 was localized to the plasma membrane and endoplasmic reticulum (ER). Functional analysis demonstrated that the transient silencing of CsCSE1 in cucumber dramatically attenuated resistance to P. xanthii, whereas overexpression of CsCSE1 in cucumber markedly increased resistance to P. xanthii. Further investigation of the abundance of lignin in transient transgenic plants revealed that CsCSE1 might actively mediate the disease resistance of cucumber by promoting lignin biosynthesis. CsCSE1 also affects the expression of its downstream lignin biosynthesis-related genes, like CsLAC, CsCOMT, CsCCR, and CsCAD. The results of this study provide targets for the genetic breeding of tolerant cucumber cultivars as well as new insights that could aid the control of plant diseases.