Caracterización funcional de la última etapa de la biosíntesis de ligninas mediante la sobreexpresión de peroxidasas en plantas modelo

Résumé

Lignins are amorphous hydrophobic polymers that are synthesized by oxidative polymerization of three p-hydroxycinnamyl alcohols. Lignins, cellulose and xylan are synthesized to form the secondary cell wall of some cell types in tissues like xylem. The last step of lignins biosynthesis is catalysed by class III peroxidases. These enzymes are hard to identify because plants present a great number of isoforms that are involved in diverse functions. In this work ZePrx, a Zinnia elegans Jacq. peroxidase previously related with lignification, was overexpressed in tobacco plants to characterize its effect on the cell wall, antioxidant systems and gene expression. The obtained results show that this enzyme is able to alter lignin S/G ratio and, as a consequence, cell wall polysaccharides without changing vascular, vegetative and reproductive development of tobacco plants. This overexpression also lead to changes in the ascorbate-glutathione cycle, suggesting a possible role of this enzyme in stress response. Besides, the overexpression of ZePrx caused the regulation of multiple genes involved in secondary cell wall formation, which supports its participation in this process.