Biology Reference
In-Depth Information
content were not affected, whereas transgenic stem stiffness was reduced
by 10-20% compared to wild-type stems. Although, the interaction of
tyrosine-rich peptides with phenolic hydroxyl groups was not confirmed,
preliminary tests indicated that the transgenic lines were more susceptible
to protease degradation and released more sugars than wild-type plants
(
Liang et al., 2008
).
III. EVALUATION OF POTENTIAL EFFECTS
OF LIGNIN-MODIFIED TRANSGENIC
TREES ON THE ENVIRONMENT
Although plants with altered lignin composition may appear robust when
grown in a controlled environment, it remains possible that in field condi-
tions, when exposed to biotic (pathogens, herbivores) and abiotic (drought,
wind, etc.) stresses, their fitness and even their capacities to develop normally
will be affected (
Bonawitz and Chapple, 2010
). The technological advantages
gained through lignin modification may be totally offset by potential reduc-
tions in fitness due to negative trophic interactions in regular plantation
environments. Likewise, little is known about any effects of lignin modifica-
tion on the flux of carbon to the surrounding environment.
A small set of studies have addressed this issue in order to determine if the
valuable technological gains from using lignin-modified trees might be offset
by environmental issues. This is probably related to the practical difficulties
in carrying out such an estimation. Most studies on GM tree trophic inter-
actions have so far been limited to observations on the evolution of popula-
tions of associated species, mostly herbivory insects.
Results from a first study on field trial-grown 4CL-downregulated trans-
genic aspen (P. tremuloides) with reduced lignins and altered growth showed
no effects of the genetic modification on growth and survival of forest tent
caterpillars (Malacosoma disstria)(
Brodeur-Campbell et al., 2006
). Effects
on feeding performance of gypsy moth (Lymantria dispar) larvae were shown
to vary among tree transgenic lines, but no potential biochemical alterations
in the transgenic lines could be directly linked to 4CL suppression (
Brodeur-
Campbell et al., 2006
).
Similarly, soil microbial community responses to altered lignin biosynthe-
sis in 4CL downregulated and/or F5H over-expressing P. tremuloides
appeared to vary among soils differing by their chemical and physical prop-
erties, but results on root biomass, diversity of microbial communities were
not consistent, making it difficult to assess any potential ecological impacts
(
Bradley et al., 2007
).
