Loss of function of folylpolyglutamate synthetase 1 reduces lignin content and improves cell wall digestibility in Arabidopsis

Abstract

BackgroundOne-carbon (C1) metabolism is important for synthesizing a range of biologically important compounds that are essential for life. In plants, the C1 pathway is crucial for the synthesis of a large number of secondary metabolites, including lignin. Tetrahydrofolate and its derivatives, collectively referred to as folates, are crucial co-factors for C1 metabolic pathway enzymes. Given the link between the C1 and phenylpropanoid pathways, we evaluated whether folylpolyglutamate synthetase (FPGS), an enzyme that catalyzes the addition of a glutamate tail to folates to form folylpolyglutamates, can be a viable target for reducing cell wall recalcitrance in plants.ResultsConsistent with its role in lignocellulosic formation, FPGS1 was preferentially expressed in vascular tissues. Total lignin was low in fpgs1 plants leading to higher saccharification efficiency of the mutant. The decrease in total lignin in fpgs1 was mainly due to lower guaiacyl (G) lignin levels. Glycome profiling revealed subtle alterations in the cell walls of fpgs1. Further analyses of hemicellulosic polysaccharides by NMR showed that the degree of methylation of 4-O-methyl glucuronoxylan was reduced in the fpgs1 mutant. Microarray analysis and real-time qRT-PCR revealed that transcripts of a number of genes in the C1 and lignin pathways had altered expression in fpgs1 mutants. Consistent with the transcript changes of C1-related genes, a significant reduction in S-adenosyl-l-methionine content was detected in the fpgs1 mutant. The modified expression of the various methyltransferases and lignin-related genes indicate possible feedback regulation of C1 pathway-mediated lignin biosynthesis.ConclusionsOur observations provide genetic and biochemical support for the importance of folylpolyglutamates in the lignocellulosic pathway and reinforces previous observations that targeting a single FPGS isoform for down-regulation leads to reduced lignin in plants. Because fpgs1 mutants had no dramatic defects in above ground biomass, selective down-regulation of individual components of C1 metabolism is an approach that should be explored further for the improvement of lignocellulosic feedstocks.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0403-z) contains supplementary material, which is available to authorized users.

Quantitative Proteomic Analysis of Alligator Weed Leaves Reveals That Cationic Peroxidase 1 Plays Vital Roles in the Potassium Deficiency Stress Response

“…Among them, secondary metabolism, photosynthesis, and the protein synthesis and degradation pathway were the top three, in which 16, 15, and 14 DAPs, respectively, were involved (Figure 4). A previous study reported that loss of function of folylpolyglutamate synthetase (FPGS) led to decreased lignin content and enhanced cell wall digestibility in Arabidopsis [23]. Thus, in our study, the high expression of FPGS in the alligator weed leaves could improve the lignin content in the cell wall in order to protect cells under LK stress.…”

Enzymatic basis for C‐lignin monomer biosynthesis in the seed coat of Cleome hassleriana

“…Based on comparisons of in vivo and in vitro enzyme activities/kinetics during the switch from G to C-lignin accumulation, it appears that the major factor driving C-lignin appearance is the loss of monolignol methylation activity. Previous studies have suggested that the methylation status of lignin can also be affected through the activity of the C1 pathway enzymes that provide the methyl donor S-adenosyl-L-methionine (Srivastava et al, 2015). To determine whether there might be changes in C1 precursor supply coincident with the appearance of C-lignin biosynthesis, we examined the levels of transcripts of key C1 pathway enzymes (protein sequences given in Dataset S4) in the Cleome transcriptome database (Dataset S5).…”

Transgenic switchgrass (Panicum virgatum L.) targeted for reduced recalcitrance to bioconversion: a 2‐year comparative analysis of field‐grown lines modified for target gene or genetic element expression

“…Field‐grown switchgrass transgenic lines with high sugar release or good growth phenotypes included those silencing or OE: (i) GAUT4, GAUT4 ‐knockdown (KD) lines down‐regulating expression of galacturonosyltransferase4 , a gene encoding an enzyme involved in pectin biosynthesis (Biswal et al ., Biswal, A.K., Atmodjo, M.A., Li, M., Yoo, C.G., Pu, Y., Lee, Y.‐C., Zhang, J.Y., Bray, A., King, Z., LaFayette, P., Mohanty, S.S., Ryno, D., Yee, K., Thompson, O.A., Rodriguez Jr, M., Winkeler, K., Collins, C., Yang, X., Tan, L., Sykes, R.W., Gjersing, E., Ziebell, A., Turner, G.B., Decker, S.R., Parrot, W., Udvardi, M.K., Mielenz, J., Davis, M.F., Nelson, R.S., Ragauskas, A.J., and Mohnen, D.); (ii) miRNA, miRNA156 ‐overexpression (OE) lines OE miRNA156, a regulator of plant developmental processes (Fu et al ., 2012); (iii) MYB4, MYB4 ‐OE lines OE PvMYB4, an R2R3‐type MYB repressor of the lignin biosynthetic pathway (Shen et al ., 2012, 2013); (iv) COMT, COMT ‐KD lines down‐regulating expression of caffeic acid O ‐methyltransferase, a lignin biosynthetic gene (Fu et al ., 2011); and (v) FPGS, FPGS ‐KD lines down‐regulating expression of folylpolyglutamate synthase 1 , a gene encoding a C1 metabolism enzyme believed to provide methyl groups for lignin biosynthesis (Srivastava et al ., 2015). …”