LACCASE5 Is Required for Lignification of the Brachypodium distachyon Culm

Abstract

The oxidation of monolignols is a required step for lignin polymerization and deposition in cell walls. In dicots, both peroxidases and laccases are known to participate in this process. Here, we provide evidence that laccases are also involved in the lignification of Brachypodium distachyon, a model plant for temperate grasses. Transcript quantification data as well as in situ and immunolocalization experiments demonstrated that at least two laccases (LACCASE5 and LACCASE6) are present in lignifying tissues. A mutant with a misspliced LACCASE5 messenger RNA was identified in a targeting-induced local lesion in genome mutant collection. This mutant shows 10% decreased Klason lignin content and modification of the syringyl-to-guaiacyl units ratio. The amount of ferulic acid units ester linked to the mutant cell walls is increased by 40% when compared with control plants, while the amount of ferulic acid units ether linked to lignins is decreased. In addition, the mutant shows a higher saccharification efficiency. These results provide clear evidence that laccases are required for B. distachyon lignification and are promising targets to alleviate the recalcitrance of grass lignocelluloses.

Silencing CHALCONE SYNTHASE in Maize Impedes the Incorporation of Tricin into Lignin and Increases Lignin Content

“…Stems of low-lignin transgenic switchgrass (Panicum virgatum) down-regulated for COMT had increased amounts of xylan, the predominant hemicellulose component in switchgrass, both when plants were cultivated in the greenhouse (Fu et al, 2011) and in the field (Baxter et al, 2014). In brachypodium (Brachypodium distachyon), the reduced lignin content of a mutant for the ligninspecific laccase BdLAC5 was compensated for by a slight increase in the content of hemicellulose, whereas the amount of cellulose remained unchanged (Wang et al, 2015b). The brown midrib mutants isolated in maize show a characteristic brown coloration of the leaf midrib that is associated with reduced lignin levels and altered lignin composition (Sattler et al, 2010).…”

Salicylic acid‐dependent immunity contributes to resistance against Rhizoctonia solani, a necrotrophic fungal agent of sheath blight, in rice and Brachypodium distachyon

“…In B. distachyon, BdCESA4 , 7 and 8 encode cellulose synthase A (CESA) proteins and the loss‐of‐function mutants for BdCESA4 and 7 showed a reduced amount of crystalline cellulose in the SCW (Handakumbura et al ., ). BdLAC5 , 6 and 10 are members of the laccase family and mutation in BdLAC5 leads to a reduction in the culm lignin level (Wang et al ., ). In our RNA‐seq analysis, BdLAC5 was induced by both SA and BTH, but BdLAC6 and 10 were found in the SA‐specific DEGs.…”

The cotton laccase geneGhLAC15enhances Verticillium wilt resistance via an increase in defence‐induced lignification and lignin components in the cell walls of plants

“…Lignin has been reported to be involved in multiple resistances, including cotton Verticillium wilt resistance (Bonello and Blodgett, 2003;Hu et al, 2018;Zhang et al, 2017). Previous studies have shown that plant laccases (LAC4, LAC11 and LAC17) are necessary and non-redundant with peroxidase for lignin polymerization in Arabidopsis (Berthet et al, 2011;Zhao et al, 2013), and that they oxidatively polymerize monolignols (p-coumaryl, coniferyl and sinapyl alcohols) into p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) lignin units (Wang et al, 2015). In this study, we isolated a lignin laccase, GhLAC15, which affected Verticillium wilt resistance by increasing total lignin and KL levels and by modifying lignin composition and structure, as well as associated cell wall traits.…”