Biology Reference
In-Depth Information
converted to fermentable sugars in the process for bioethanol production.
Preliminary analyses on wood samples from 1-year-old field-grown coppices
provided very encouraging results with
50% increase in saccharification
potential ( Van Acker et al., 2011 ).
Likewise, CCR-downregulated transgenic Norway spruce plants (Picea
abies) were produced by particle bombardment of embryogenic cultures
with a construct harbouring the homologous PaCCR gene in an antisense
orientation under the control of the maize ubiquitin promoter. The most
affected 5-year-old transgenic plants, with about 60% residual CCR tran-
script levels, exhibited altered lignin contents (up to 8% reduction) and
compositions, with a reduced quantity of H units in the non-condensed
lignin fraction ( Wadenb ยจ ck et al., 2008 ). Five- to six-year-old greenhouse-
grown transgenic spruce plants appeared normal but had reduced stem
diameters (up to 20%) compared to control plants. Furthermore, small-
scale Kraft pulp assays carried out with CCR-downregulated spruce
wood indicated a better delignification with a 3.5% reduction in the
kappa number.
I. CINNAMYL ALCOHOL DEHYDROGENASE
Cinnamyl alcohol dehydrogenase (CAD) catalyses the last step of the mono-
lignol biosynthetic pathway that is the conversion of cinnamyl aldehydes into
their corresponding alcohols.
The spatial and developmental regulation of the CAD gene was assessed
in transgenic poplars (INRA 717-1B4 P. tremula
P. alba) transformed with
a chimeric gene fusion of a eucalyptus CAD gene promoter with the uidA
reporter gene. In greenhouse-grown plants, a specific GUS expression was
detected in the vascular tissues of stems, roots, petioles and leaves. In
addition, GUS activity appeared preferentially localized in xylem ray cells
and parenchyma cells surrounding sclerenchyma fibres ( Feuillet et al., 1995 ),
but also in vessels and fibres undergoing lignification ( Hawkins et al., 1997 ).
These transgenic poplar plants were subsequently planted in the field in order
to evaluate the pattern of expression of the CAD gene in trees grown under
natural conditions. This analysis was done on trees derived from 20 different
transgenic events. Overall, the tissue specificity of the CAD promoter
appeared to be conserved and stable in field conditions over an extended
period ( Hawkins et al., 2003 ).
Incorporation of a sense or antisense
copy of a CAD poplar
(P.
trichocarpa
P. deltoides) gene transgenic poplars
(INRA clone
717-1B4, P. tremula
P. alba) resulted in CAD downregulation with 30%
Search WWH ::




Custom Search