Suppression of Arabidopsis peroxidase 72 alters cell wall and phenylpropanoid metabolism.

Class III peroxidases are glycoproteins with a major role in cell wall maturation such as lignin formation. Peroxidases are usually present in a high number of isoenzymes, which complicates to assign specific functions to individual peroxidase isoenzymes. Arabidopsis genome encodes for 73 peroxidases, among which AtPrx72 has been shown to participate in lignification. Here, we report by using knock out peroxidase mutants how the disruption of AtPrx72 causes thinner secondary walls in interfascicular fibres but not in the xylem of the stem. This effect is also age-dependent, and AtPrx72 function seems to be particularly important when lignification prevails over elongation processes. Finally, the suppression AtPrx72 leads to the down-regulation of lignin biosynthesis pathway, as well as genes and transcription factors involved in secondary wall thickening.