Reduced Leaf Peroxidase Activity is Associated with Reduced Lignin Content in Transgenic Poplar

A cationic peroxidase gene (Shpx6a) of a forage legume species, Stylosanthes humilis, was transferred to poplar (Populus tremula) in antisense orientation under the control of 35S RNA promoter of cauliflower mosaic virus. Transformed plants were regenerated on selective media after co-cultivation of poplar stem explants with Agrobacterium tumefaciens and integration of transgenes was confirmed by PCR and Southern hybridization analyses. Analyses of selected transgenic plants showed reductions in total leaf peroxidase activity which was 50% to 70% of that measured in untransformed control plants. Transgenic poplar plants with reduced leaf peroxidase activity had 10-20% lower lignin content than control plants. Although which isoform of poplar peroxidase (s) has been inhibited by 35S-Shpx6a antisense construct is not clearly known, our results suggested the possibility of manipulation of lignin content through inhibition of lignin-specific peroxidases.