The in vivo impact of MsLAC1, a Miscanthus laccase isoform, on lignification and lignin composition contrasts with its in vitro substrate preference

Abstract

BackgroundUnderstanding lignin biosynthesis and composition is of central importance for sustainable bioenergy and biomaterials production. Species of the genus Miscanthus have emerged as promising bioenergy crop due to their rapid growth and modest nutrient requirements. However, lignin polymerization in Miscanthus is poorly understood. It was previously shown that plant laccases are phenol oxidases that have multiple functions in plant, one of which is the polymerization of monolignols. Herein, we link a newly discovered Miscanthus laccase, MsLAC1, to cell wall lignification. Characterization of recombinant MsLAC1 and Arabidopsis transgenic plants expressing MsLAC1 were carried out to understand the function of MsLAC1 both in vitro and in vivo.ResultsUsing a comprehensive suite of molecular, biochemical and histochemical analyses, we show that MsLAC1 localizes to cell walls and identify Miscanthus transcription factors capable of regulating MsLAC1 expression. In addition, MsLAC1 complements the Arabidopsis lac4–2 lac17 mutant and recombinant MsLAC1 is able to oxidize monolignol in vitro. Transgenic Arabidopsis plants over-expressing MsLAC1 show higher G-lignin content, although recombinant MsLAC1 seemed to prefer sinapyl alcohol as substrate.ConclusionsIn summary, our results suggest that MsLAC1 is regulated by secondary cell wall MYB transcription factors and is involved in lignification of xylem fibers. This report identifies MsLAC1 as a promising breeding target in Miscanthus for biofuel and biomaterial applications.

Substrate Specificity of LACCASE8 Facilitates Polymerization of Caffeyl Alcohol for C-Lignin Biosynthesis in the Seed Coat of Cleome hassleriana

“…However, the substrate preference of ChLAC8, particularly the apparent lack of activity with coniferyl alcohol, is indeed unusual. Laccases from sycamore maple (Acer pseudoplatanus), Miscanthus, and maize (ZmLAC3) exhibit a preference, but not an absolute selectivity, for sinapyl alcohol over coniferyl alcohol (Sterjiades et al, 1992;He et al, 2019;Xie et al, 2020). This is consistent with a proposed mechanism that favors the presence of methoxyl groups in the substrate to be oxidized (Ramalingam et al, 2017) and the importance of interactions between the 5-methoxyl group of sinapyl alcohol and ZmLAC3 (Xie et al, 2020).…”

“…Laccases are a large group of multicopper oxidases that are widely distributed in bacterial, fungi, animals, and plants. Recent advances in high-throughput sequencing technology and molecular biology have allowed several laccases that participate in lignin polymerization to be characterized in multiple plant species (Cheng et al, 2019;He et al, 2019;Le Bris et al, 2019;Wang et al, 2019;Simões et al, 2020).…”

“…Whether laccases can control lignin composition is currently unclear. Studies to date suggest that cell wall laccases are relatively promiscuous with respect to monolignol specificity in vitro, and the impact on lignin composition of their modified expression in planta cannot necessarily be predicted (He et al, 2019). Identification of laccases and/or peroxidases specifically involved in C-lignin polymerization would facilitate the introduction of C-lignin into non-seed-coat tissues of bioenergy crop plants as a co-product for bioprocessing (Ragauskas et al, 2014).…”

Identification of key modules and hub genes regulating drought stress response in rice drought sensitive line PY6 by weighted gene co-expression network analysis

“…Moreover, it has been demonstrated that laccases were regulated by MYB TFs and involved in lignin biosynthesis in secondary wall formation of Arabidopsis and Miscanthus (He et al 2019;Zhou et al 2009); as well, a rice laccase encoding gene OsChi1 was reported that played an important role in the ROS signaling pathway (Cho et al 2014), suggesting that, in present study, MYB TFs-regulated laccases with the differential expression alteration participated in the improvement of drought stress tolerance (Fig. 8).…”

Weighted Gene Coexpression Network Analysis-Based Identification of Key Modules and Hub Genes that Regulate the Drought Stress Response in the Rice Drought-Sensitive Line PY6

“…Moreover, it has been demonstrated that laccases are regulated by MYB TFs and are involved in lignin biosynthesis in secondary wall formation of Arabidopsis and Miscanthus [67,68]. Additionally, a rice laccase-encoding gene, OsChi1, has been reported to play an important role in the ROS signaling pathway [66], suggesting that, in the present study, MYB TF-regulated laccases with differential expression are involved in the improvement of drought stress tolerance (Fig.…”