LIGNIN-SPECIFIC LACCASES, NEW TARGETS FOR THE GENETIC ENGINEERING OF LIGNIFICATION

摘要

While it is established that peroxidases are involved in the polymerization of lignins, it is not yet clear whether laccases participate to lignification. In order to address this issue, we studied laccase T-DNA insertion mutants in the model plant, Arabidopsis thaliana. We identified two genes, AtLAC4 and AtLAC17, particularly expressed in stems. AtLAC17 was more specific to fibers while AtLAC4 was expressed in vascular bundles and fibers. We produced a double mutant, Iac4 lac 17, by crossing a lac17 mutant with a Iac4 mutant. The analyses of the single and double mutants provided the first evidence that laccases are involved in the constitutive lignification of Arabidopsis stems. The lower lignin levels of the double mutant resulted in higher saccharification yields. These findings suggest that the genetic engineering of lignin-specific laccases is a potentially innovative and promising tool to facilitate the lignocellulose-to-bioethanol conversion process.