The PMT-driven p-coumaroylation of poplar lignins impacts lignin structure and improves wood saccharification

ABSTRACTTransgenic poplars (Populus tremula x Populus alba, clone INRA 717-1B4) were produced by introducing the Brachypodium distachyon Bradi2g36910 (BdPMT1) gene driven by the Arabidopsis (Arabidopsis thaliana) Cinnamate 4-Hydroxylase (AtC4H) promoter in the wild-type (WT) line and in a line overexpressing the Arabidopsis Ferulate 5-Hydroxylase (AtF5H). BdPMT1 encodes a transferase which catalyzes the acylation of monolignols by p-coumaric acid (CA). Several BdPMT1- OE/WT and BdPMT1-OE/AtF5H-OE transgenic lines were grown in the greenhouse and BdPMT1 expression in xylem was confirmed by RT-PCR. The analysis of the cell walls (CW) of poplar stems and of corresponding purified dioxan lignins (DL) revealed that the BdPMT1-OE lignins were as p-coumaroylated as the lignins of C3 grass straws. For some transformants, CA levels even reached about 11 mg/g CW and 66 mg/g DL, which by far exceeds those of Brachypodium or wheat samples. This unprecedentedly high p-coumaroylation of poplar lignins affected neither the poplar growth, nor the stem lignin content. By contrast, the transgenic lignins were structurally modified, with an increase of terminal units with free phenolic groups. Relative to controls, this increase argues for a reduced polymerization degree of BdPMT1-OE lignins and makes them more soluble in cold NaOH solution. The p-coumaroylation of poplar samples, up to the levels of C3 grasses, improved the saccharification yield of alkali-pretreated poplar CW. These results establish that the genetically-driven p-coumaroylation of lignins is a promising strategy to make wood lignins more susceptible to the alkaline treatments that can be used during the industrial processing of lignocellulosics.One-sentence summaryThe expression of a grass p-coumaroyl-CoA:monolignol transferase induces a high p-coumaroylation of poplar lignins and a better saccharification of alkali-pretreated poplar wood without growth penalty

Lignin Content and Resistance to Sclerotinia minor in Peanut

ABSTRACT Lignin has been shown to be an important component for plant defense in several pathosystems, but the relationship between peanut stem lignin content and resistance in the field to Sclerotinia blight has not been investigated. Stem lignin was quantified from twenty runner, six virginia, and ten spanish genotypes grown in the greenhouse using the acetyl bromide method. Significant differences in lignin content were found within the runner and spanish entries, but not among the virginia genotypes. Disease data collected in the field over two to three years were used to test correlations between lignin content and Sclerotinia blight resistance for a subset of the runner and virginia entries. No significant correlations were found. Within the runner entries, the highest and lowest stem lignin content was found in entries with the most disease resistance. These results indicate that preformed stem lignin content is not a reliable predictor for resistance to Sclerotinia blight in peanut. In addition, commercial peanut cultivars appear to vary considerably in lignin content, and the genotypes with lower levels of stem lignin may be useful to producers who can use peanut haulm for animal feed. Southwest Runner, a cultivar with high resistance to Sclerotinia blight, had the lowest stem lignin content of the 36 peanut lines tested.

Jute (Corchorus olitorius var. O-72) stem lignin: variation in content with age

Stem lignin content of a mature jute plant was found to be around 29% giving a deposition rate of 0.21% per day. The study was made on individual plants of different ages starting from five weeks when they were big enough to produce sufficient dry mass for lignin estimation to 16 weeks of age when a jute plant is ready for retting. An intense rate of increase (1.15%) was found during the 7th week of growth, probably due to a rise in temperature. Present data and the average rate of increase of lignin production can be considered as a reference value for projects working on producing low-lignin - jute varieties. DOI: http://dx.doi.org/10.3329/bjb.v43i3.21603 Bangladesh J. Bot. 43(3): 309-314, 2014 (December)