[To contribute to this conference, send your message to
For further information on the Electronic Forum on Biotechnology in Food and
Agriculture see Forum website.
NB - participants are assumed to be speaking on their own behalf, unless they state otherwise.]
Sent: 03 July 2002 09:19
Subject: 104: Reduced lignin from GM forest trees
From Professor Joe Cummins, Canada.
"Reduced lignin by genetic modification of forest trees: Benefit or detriment?"
Plant cell wall material is composed of three important constituents: cellulose, lignin, and hemicellulose. Lignin is particularly difficult to biodegrade, and reduces the bioavailability of the other cell wall constituents. Lignin is a complex polymer of phenylpropane units, which are cross-linked to each other with a variety of different chemical bonds. This complexity has thus far proven as resistant to detailed chemical characterization as it is to microbial degradation. Nonetheless, some organisms, particularly fungi, have developed the necessary enzymes to break lignin into its component chemicals.
Extensive efforts have been made to genetically modify trees so that they have reduced lignin to facilitate pulp production. Forage crops have also been modified to facilitate grazing and to allow animals digest more of the forage or silage. Most of the genetic modifications included the use of anti-sense gene constructs to inhibit particular gene products for the metabolic path of lignin production. Anti-sense modifications use the insertion of genes that produce messenger RNA with a sequence providing an A to complement each U in the lignin message and G for C in the message, U for A and C for G. The anti-sense message forms an RNA double helix with the lignin message and that double helix is mistaken for a replicating RNA virus by the plant cell post-transcriptional gene silencing system and it is destroyed. Lignin is implicated in plant resistance to stress and pathogens, so the desirable low lignin tree or forage crop may be too delicate to thrive in the real world (outside the green house).
Low lignin anti-sense transgenic poplars were grown for four years produced high quality pulp without interfering with plant growth and fitness (1). Another low lignin anti-sense poplar was found to have a low lignin content but the structure of the lignin was altered in a manner that was less amenable to industrial lignin degradation than the normal tree (2). An extensive study of low lignin perennial herbaceous plants (including alfalfa, brome grass and orchard grass), that had been selected using conventional breeding, had problems including decreased winter survival and decreased biomass (3). Presently, the transgenic anti-sense low lignin trees need extensive testing with exposure to environmental stress and to pests before extensive plantations are produced. Detrimental impacts of low lignin anti-sense should be reported promptly, fully and truthfully.
Boerjan,W,Schuch,W,Coirnu,D and Halpin,C "Field and pulping performance of
trees with altered lignification" 2002 Nature Biotech 20,607-13
2.Jounanin,L,Goujon,T,Nadai,V,Martin,M,Mila,I,Vallet,C,Pollet,B,Yoshinaga,A, Chabbert,B,Petit-Conil,M and Lapeire,C "Lignification in transgenic poplars with extremely reduced caffiec acid O-methyl transferase activity" 2000 Plant Physiology 123,1363-73
3. Caler,M,Buxton,D and Vogel,K "Genetic modification of lignin concentration affects fitness of perennial herbaceous plants" 2002 Theor Appl Genet 104,127-31
Professor Joe Cummins,
University of Western Ontario.
jcummins (at) uwo.ca
Sent: 03 July 2002 09:24
Subject: 105: Re: Managing gene flow in the South.
Jane Morris (Message 102, July 2) acknowledges the loss of export markets due to GE contamination as a real risk from unexpected/uncontrolled gene flow. This is even truer for developing countries dependent on a few agricultural products for export. The recent report from Australia that herbicide-resistance genes can flow up to 3 km from source fields further confirms this risk. Even if the initial levels of contamination are low, the contamination will get eventually worse if farmers save their seed for subsequent planting, which remains a widespread practice among farmers in developing countries. Unlike Australia or the US, farms in developing countries also tend to be much smaller and closer together, increasing the risk of gene escape and subsequent contamination.
I would also add that the proven market preference nowadays for GE-free products is a very strong reason for developing countries, like the Philippines, to keep their entire territory GE-free, by avoiding field releases including field-testing. Then, we can easily guarantee GE-free exports, with minimum effort in testing and segregation.
In countries where transgenic gene flow is already occuring and spreading, a GE-free guarantee -- if it can be given at all -- can only be given at high cost and often only means <1% contamination.
Developing countries that can remain truly GE-free will enjoy a huge competitive advantage vis-a-vis these countries.
Secretary-general, Philippine Greens
rverzola (at) gn.apc.org
Sent: 03 July 2002 14:35
Subject: 106: Soil mercury remediation by transgenic trees
[Thanks to Professor Cummins for raising another aspect concerning gene flow from GM populations. I will also use this occasion, to remind you all that there are just 3 days left for posting messages in this conference. The final day for posting messages is July 5. There will be no extension past that date. I will then post the last messages on Saturday morning (Rome time) and the conference is then be closed. I will thus repeat what I said last week: For those of you who have not yet participated in the conference with your views or experiences (or for those of you who have already contributed, but still have something you wish to say) our message is "Speak now, or forever hold your peace".........Moderator]
Soil mercury pollution can be a major chronic pollution hazard. Most of the sites are historical industrial sites. Gold mining, in particular, may still use primitive "quicksilver" gold extraction that pollutes soil and waterways. In many areas, the soil pollution may be of geological origin rather than a result of human activity.
Currently, atmospheric deposition of mercury is a leading pollution problem in the cities and wild lakes of the northern countries. Most of the problem is associated with fossil fuels and medical waste incineration. Plots of land that are polluted with high levels of mercury are planned to be phytoremediated using trees that are modified to take up the ionic mercury or organic mercury, convert it to less toxic elemental mercury, then expel it into the atmosphere where it will be safely diluted before it is diluted (1,2,3).
The environmental risk assessment by the proponents of transgenic phytoremediation argued that mercury emissions from the treated sites would be below the current emission levels for elemental mercury. Elemental mercury is retained in the atmosphere for up to two years, during which time it is diluted to "non toxic" levels before precipitation (4). The proponents also argued that it would be negligible in comparison to fossil fuel burning and hospital waste incineration (4). Finally, the proponents argued that feeding animals would be exposed to less mercury than from conventional plants because elemental mercury was so rapidly released from the plant tissue (4). The proponents believed that the genes from mercury emission would not be transferred to non-transgenic plants (4).
The proponents' risk assessment seemed very uncritical and quite unrealistic. Elemental mercury does remain in the atmosphere for up to two years, but always precipitates in rain and snow. The arctic acts as a trap to condense the fallen mercury but all of the northern communities, including large eastern North America cities, suffer growing mercury accumulation from precipitation. It is clear that the precipitated elemental mercury is rapidly converted to ionic and organic mercury once it is deposited.
What phytoremediation will do is to relocate soil mercury from contaminated soil sites in southerly communities and redistribute the mercury to the northern communities. There are a large number of sites with mercury-contaminated soil and sediment, along with the geological areas of high mercury content. For example, the crude gold mining techniques used along the Amazon left elevated soil mercury levels. If that area was to be phytoremediated the mercury released to the atmosphere would likely precipitate in the cities on northern United States and Canada and impact heavily in the Arctic. Emitted mercury condensed in the ocean will reappear on the dinner tables of the world from bioaccumulation through the food chain.
Based on the current experience with transgenic crops it is certain that some transgenic pollen and seed will escape. Populating expansive areas of geological mercury pollution with mercury transgenic trees (which would be selected for) could lead to a global catastrophe. The US Environmental Protection Agency (EPA) seems rather schizophrenic in supporting the research on mercury phytoremediation by air emission while supporting major projects in reducing atmospheric mercury deposition. The United Nations should play a major role in regulating the global atmospheric deposition of mercury and other volatile pollutants.
1. Rugh,CL, Senecoff,J, Meagher,RB and Merkle,SA. "Development of transgenic
yellow poplar for mercury phytoremediation" 1998 Nature Biotech 16,925-928
2. Bizily,SP ,Rugh,CL and Meagher,RB. "Phytodetoxification of hazardous
organomercurials by genetically engineered plants" 2000. Nature Biotech. Nat Biotechnol, 18(2): 213-217.
3. Kramer,U and Chardonnens,A. "The use of transgenic plants in the bioremediation of soils contaminated with trace elements" 2001 Appl Microbiol Biotechnol. 55,661-72
4. Pilon-Smits,E and Pilon,M. "Breeding mercury-breathing plants for environmental cleanup". 2000. Trends in Plant Science 5,235-6
Professor Joe Cummins,
University of Western Ontario.
jcummins (at) uwo.ca