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Inhibition of two laccases for obtaining or selecting plants of agronomic interest having a reduced lignin content

A group of researchers coordinated by Lise Jouanin has inhibited two laccase enzymes in plants resulting in alteration of lignification. The production of plants and trees having a reduced lignin content will be useful for the production of biomass for the bioethanol and pulp industries, and for animal nutrition (forage)

Phenotype of lacasse mutants. Arabidopsis thaliana plants grown in the growth chamber (long-day conditions: no phenotype was observed). See Berthet et al., The Plant Cell, Vol. 23: 1124–1137, March 2011. © INRA
Updated on 11/26/2013
Published on 11/18/2013

The lignin content of plants has a major influence on their industrial uses. For example, it affects the nutritional value of plants for animal feed, as well as the performance of papermaking processes, and the yield of bioethanol. In this context and in the framework of a Génoplante programme, a research group steered by Dr. Lise Jouanin aimed to establish whether mutations in laccase genes - that encode enzymes involved in polymerization of lignin precursors - had an effect on the lignin content of the mutant plants and on the qualitative (structural) properties of lignin.

Arabidopsis thaliana lines having T-DNA insertions in LAC4 and LAC17 genes were identified and characterized. Thioacidolysis notably revealed that LAC17 is involved in the early stage of lignification accompanying the deposition of guaiacyl lignin units in fibers. The researchers found that the lac4 and lac17 mutants have a reduced lignin content (from 8% to 14%) determined on mature dry stems. The lac4 mutants displayed moderately higher levels of saccharification than the wild-type and, by contrast, lac17 mutant was no more easily hydrolyzed than control samples. Moreover, researchers have obtained double mutants, amongst them lac4.2/lac17 mutant exhibited a very reduced lignin content (40% compared to the wild-type) and an increased saccharification yield (62%) compared to the wild-type (28%). Researchers have identified orthologs of AtLAC4 and AtLAC17 in numerous plants (model plants and plants of agronomic interest), and produced A. thaliana, Brachypodium distachyon, maize, rice and poplar transgenic lines over-expressing under different promoters the miR397 microRNA, which is capable of inhibiting the expression of several laccases. Preliminary results showed a decrease in lignin content and an increased digestibility in Brachypodium plants, as well as a reduced lignin content in poplar cell walls.

This invention is dealing with a method for selecting or obtaining plants with a reduced lignin content and in which the cellulose hydrolysis of walls is increased. It consists in simultaneously reducing the gene expression of two laccases, orthologs of AtLAC4 and AtLAC17, through various techniques such as TILLING, directed mutagenesis, marker-assisted selection, plant transformation (gene silencing (microRNA), etc. Thus, obtaining plants of agronomic interest such as cereals (maize, sorghum, sugar cane, rice, etc.) and trees (poplar, eucalyptus, etc.) with a reduced lignin content will be useful to improve digestibility of forage for ruminants, bioethanol production, or the production of pulp for the paper industry.

INRA Transfert is seeking industrial partners to further develop this patented technology (WO2010/143154; FR, EP, USA, CA, AU; Génoplante-Valor, INRA), through licence or licence option with a R&D programme.

Contact(s)
Scientific contact(s):

  • Lise JOUANIN Institut Jean-Pierre Bourgin, INRA Versailles
Technology transfer officer, Inra transfert, 28, rue du Dr. Finlay, 75015 Paris, France:
Claire LEMONTEY (+33 1 42 75 92 96)
Associated Division(s):
Plant Biology and Breeding, Science for Food and Bioproduct Engineering
Associated Centre(s):
Versailles-Grignon

Sources

  • Berthet et al., The Plant Cell, Vol. 23: 1124-1137, March 2011
  • Le Bris et al., The XIIIth  Cell Wall Meeting, 7-12 July 2013, Nantes, France