Biology Reference
In-Depth Information
2006
). Likewise, preliminary analyses found higher wood density compared
to control wood material. Furthermore, technological analyses revealed that
paper of equal or better quality could be made from pulp fibre derived from
pC4H-F5H transgenic trees, due to a higher degree of polymerization (DP)
of the residual pulp cellulose, while yielding significant savings in pulping
process time and chemicals both for pulping and bleaching.
In a recent communication at the International Scientific Conference on
Hardwood Processing (October 16-18, 2011, Virginia Tech, Blacksburg, VA,
USA), Maud Hinchee reported ArborGen analyses for the properties of
wood collected from 4-year-old transgenic over-expressing F5H eucalyptus
trees grown in the field. These analyses indicated an S/G ratio of 4.6 in the
transgenic wood compared to 2.3 in the wild type. This increased ratio
appeared positively correlated to soluble lignin content and to the produc-
tion of good quality pulp using a smaller amount of alkali (decrease from
21% used for wild-type wood down to 16.5%) that resulted in a 15% reduc-
tion in chemical cost and also an improved pulp yield (
Hinchee, 2011
).
F. CAFFEOYL-COA O-METHYLTRANSFERASE
Caffeoyl-CoA O-methyltransferase (CCoAOMT) catalyses methylation
of caffeoyl CoA to generate feruloyl-CoA (
Pakush et al., 1989
). Two
CCoAOMT genes were identified in poplar and characterized for their expres-
sion pattern detected either by immunolocalization or by promoter activity in
poplars transformed by CCoAOMT promoter-uidAfusion(
Chen et al., 2000
):
both genes were expressed similarly in xylem but differentially in phloem; they
were also both induced after wounding, fungal infection and bending. Further,
the same research team produced transgenic poplars with strongly reduced
CCoAOMT activity resulting, as analysed in 6-month-old greenhouse-grown
plants, in a small decrease in Klason lignin content (up to 12%), a slight
increase in S/G ratio and a strong accumulation of soluble phenolic acid
glycosides (
Meyermans et al., 2000
). These modifications were associated
with a pink-red colouration of the active xylem and an enhanced fluorescence
of mature vessel cell walls, with no apparent effects on tree growth and
development. Two transgenic lines with strong and stable CCoAOMT down-
regulation are presently evaluated in the field in France: these trees exhibit
normal growth and development.
Zhong et al. (2000)
also generated transgenic poplar plants with reduced
CCoAOMT activity using an antisense strategy. Interestingly, both studies
were performed on the same poplar clone (INRA 717-1B4 P. tremula
P. alba)withCCoAOMT poplar sequence (in sense or antisense orientation)
