The genetically modified poplar exhibits modified lignin (a major
constituent of wood) due to the decreased activity of an enzyme of
the lignin biosynthetic pathway. The altered enzyme is CCR
(Cinnamoyl coenzymeA reductase). The down-regulation has been
obtained by co-suppression. The enzyme residual activity varies
between 3 to 100 % and is not necessarily uniform within the plant.
Consequently, the quality or/and quantity of lignin is modified.
These modifications and the consequences on some wood properties
have been described in several publications (Baucher et al., 1996,
van Doorsselaere et al., 1995 ; Meyermans et al., 2000 ; Lapierre
et al., 1999 ; Pilate et al., 2002 ; Lapierre et al., 2004).
In addition, the transgenic lines have also integrated the
hygromycin phosphotransferase (hpt) gene that confers resistance to
the antibiotic hygromycin. This antibiotic resistance is needed
during in vitro culture steps to select cells that have been
genetically modified from those that have not been modified.