Insect resistance, Herbicide resistance and Floral modification

1. ECOLOGICAL CONSEQUENCES IN BIODIVERSITY AND BIOTECHNOLOGY IN
FORESTRY
Introduction
With the increasing recognition of world population feeding and health, global climate
change and biodiversity loss, and limited energy resources with fossil fuels calling for alternatives
such as biomass crops, the relevance of forestry for human well-being in the future is more than
evident.The applications of biotechnological methods including genetic engineering, marker-
assisted breeding, clonal propagation of elite trees, etc., are becoming very important.
Genetically modified trees:
First genetically modified trees
The first regeneration of a genetically modified (GM) forest tree was achieved in 1986 in
Populus. Since then, the genus has become a model for genetic modification and related tree
biotechnology studies. The first attempt to genetically modify a conifer (Larix) was reported in
1991 (Huang 1991). Introducing targeted genes into the genome of a forest tree is a way to obtain
GM plants. It is also a basic research tool for a better understanding of gene functioning in woody
plants.
China commercially released 1.4 million genetically modified Poplar (Populus) trees in an
area of 300 – 500 hectares (Food and Agriculture Organization of the United Nations, 2004). This
event marked the first biotech forest tree ever released into the environment. These trees were
predominately modified with the Bt gene that produces a protein toxic to insect pests. This gene is
produced by a bacterium in the soil called Bacillus thuringensis and is used in a number of biotech
crops including corn, cotton, and soybeans. Today there are spurious reports that these trees are
now readily available to tree farmers to plant for various purposes.

2. Effects in Target and Non-target Pests
The singly most common transformation for pest resistance involves the introduction of
exogenous Bt genes, enabling the plant to produce Cry toxins lethal to certain targeted insect
pests. More than 150 different Cry proteins have been identified (with examples including
Cry3A a proteins targeting coleopteran insects and the Cry1 and Cry2 families effective against
lepidopteran species.
The effectiveness of Bt toxins against specific pest species on trees has been tested and verified
both in laboratory . Most studies report significant reduction of consumption and performance of
target insect pests on Bt trees. Genissel (2003) found that ingestion of Populas leaves from Bt
aspens induced 100% mortality in Chrysomela tremulae within 2–13 days depending on instar,
with older instars and adult beetles living the longest. Bt induction in Pinus radiata induced up to
80% mortality in larvae of the painted apple moth.
Insect resistance
Mode of action of insect resistance gene
 The first strategy consists of using micro projectiles to insert a gene encoding an
endotoxin which binds to the receptors in the intestine of Lepidoptera, Coleoptera
and Diptera, lysing the organ and killing the insect.
Examples :
This was done in Populus alba × P. grandidentata, P. tremula × P. tremuloides and Picea
glauca. GM Populus trees and Pinus radiata expressing the Bacillus thuringiensis endotoxin ‘Bt’
have been obtained.
 A second transformation method is based on the introduction of a gene coding for
a protease inhibitor that modifies insect digestion, causing the death of the pest.

3. Examples:
Studies used potato gene pin2, a protease inhibitor introduced into P. alba ×
P. grandidenata through A. tumefaciens (Klopfenstein 1991), and the gene of a rice protease
inhibitor introduced into P. tremula × P. tremuloides (Heuchelin 1997).
 A third approach focuses on simultaneous modification of two genes for enhanced
resistance to insects. This was achieved in Liquidambar styraciflua, combining a
peroxidase anionic enzyme gene involved in inhibiting cell growth and wall
development with a ‘Bt’ gene (Sullivan and Lagrimini 1993).
Herbicide resistance
A first method has consisted in introducing a mutated version of the gene encoding the
enzyme target for various herbicides: glyphosate for Populus alba × P. grandidentata,
P. trichocarpa × P. deltoides, Eucalyptus grandis, Larix decidua and Pinus radiata (the herbicide
blocks the synthesis of tryptophan, tyrosine and phenylalanine), or chlorosulfuron for Populus
tremula and Pinus radiata (the herbicide blocks the synthesis of leucine, isoleucine and valine).
A second and more frequently used strategy consists of introducing a microbial gene
encoding an enzyme for the detoxification of the herbicide, and has been applied to Populus alba,
P. alba × P. tremula, P. tremula × P. alba, P. trichocarpa × P. deltoides and Eucalyptus
camaldulensis and Pinus radiata and Picea abies .
Flowering modification
In order to produce sterile trees and prevent possible dispersal of transgenic pollen in the
environment, an approach based on genetic ablation has been tested on poplar . This technique,
which consists of expressing a cytotoxic gene under the control of a very specific poplar floral
promoter, resulted in more than 90 percent of transformed lines lacking floral structures. Other
approaches, based on the suppression of key flowering genes, are being tested.

4. Quantitative and qualitative modification of lignin
Modification of lignin composition or content is being actively pursued because of the
expected financial gains from pulp processing improvements. Lignins, which enhance cell wall
mechanical properties and hardness, are difficult to process and are a significant limitation in
processing wood into paper pulp by chemical treatment. Genetic transformation to modify lignin
characteristics is a key research feature on species used in the paper industry. The aim is to regulate
the activity of key enzymes involved in the lignin biosynthesis pathway. Active on-going research
targets the effects of lignin biosynthesis in Populus on soil carbon transformation and storage.
Preservation of plywood
Cost of wood contributes more than 80 % to the variable cost of unbleached chemical
pulp. Contaminating organisms that degrade cellulose or cause staining of wood can, therefore,
have a significant impact by reducing yields of chemical pulp (10) or necessitating bleaching of
mechanical pulp (11). Bio pulping fungi are inoculated at high dosages and incubated under
conditions that favour their ability to colonise and compete with undesirable organisms. These
fungi are thus able to protect pulpwood against decay and staining organisms.
In vitro shoot proliferation and in vitro and ex vitro root formation of Pyrus elaeagrifolia
Pallas
Shoot-tip cultures of Pyrus elaeagrifolia Pallas, an important gene source for drought and
chlorosis resistance in pear rootstock breeding, were established from a wild mature tree originated
from seed. Murashige and Skoog basal medium supplemented with different concentrations of
benzyladenine (BA) singly or in combination with auxin was used in the study.
Conclusion
In today’s world, in which the increasing demand of agricultural products and the changing
needs of raw materials and environmental pressures are threatening all natural ecosystems,
particularly the forest ecosystems, is specially important the knowledge and conservation of forest
resources. Biotechnology offers new tools for complementing classical Forest Tree Improvement
methodologies in order to manage Forest Genetic Resources (FGR).

5. References
www.responsibleuse.org/material/biotechtrees.html.
journal.frontiersin.org/.../ecological-consequences-of-biodiversity-and-bi...
social-ecology.org/wp/1996/04/biotechnology-vs-biodiversity.