PULP (science) FICTION

PULP (science) FICTION Marcin Stawowczyk

Our civilization depends on trees and their wood. We can say that if there hadn’t been any trees there would not be also human civilization. We use their wood to build houses and furniture, to produce paper and to burn it as a fuel

However our irresponsibility as well as constant growth of human population resulted in terrifying destruction of worldwide forests.

Most of the specialists agree that destruction of tropical ( and also boreal ) forests is mainly caused by big corporations that use their wood for paper production In the age of e-mails, Internet and on-line newspapers we could speculate that the need for paper should decline. But it’s only partially true...

One of saddest fact is that a lot of high-quality wood is being destroyed during paper production. And the the cause of that is in the plants’ cell walls

Process called lignification normally enhances plant cell walls Lignin is a amorphic substance which accumulates in celll walls. It makes them stronger, less prone to high pressure damages and takes part in water transport. The main components of lignin are polyphenols.

However paper containing lignin is weak and we can say „has an accelerated >>aging process<<„ As a result a complicated process of lignin removal has to be performed During that process wood is treated with sulphuric acid or strong alkalia. In the consequence a lot of precious cellulose is being wasted A substances arising as a result of that is called PULP

Scientists concluded that if the lignin is the main problem during pulping process it would be nice to have trees which do not produce the lignin. Of course such trees wouldn’t be higher than a grass so biotechnologists decided to find balance between amount of lignin which is sufficient to enable growth but it’s low enough to make the pulping process more efficient. This was not very easy task. A process of lignin synthesis is a bit... let’s say... complicated

However the base process is not a very difficult. Lignin consist with many different monomers which most popular from are shown below... It’s not difficult to guess that their precursor must be phenyloalanine ( tyrosine is an animal aminoacid)

Phenyloalanine is being transformed to many derivative substances. Among them there are cinnamic alcohol and ferulic acid. These compounds are being also modified...

Some phenyloalanine derivatives are conjuatd with hydroxycarbonates They are also responsible for lignin creation

Scientists decide to decline lignin production by blocking important enzymes cinnamyl alcohol dehydrogenase ( CAD ) and caffeate/5-hydroxyferulate O-methyltransferasse (COMT)

Tree chosen for that experiment was a poplar ( topola ;) which main advantage is very quick growth rate. Poplars can be used for growing „artificial forests” which would be totally cut down for wood saving natural forests instead

The poplars were transfected with antisense RNA coding DNA for CAD or COMT ( but not both those enzymes ). The procedure was standard for transgenic plants including preselection on Petri dishes and growth in greenhouse. But in these case a crucial point were field trials...

Plants were divided into two groups, one was localized in UK and the second in France. Every group included five populations: 1. Wild type ( control group) 2. Antisense COMT line ASOMT2B 3. Antisense COMT line ASOMT10B 4. Antisense CAD line ASCAD21 5. Antisense CAD line ASCAD52 However there were only 10 trees per group in UK and 12 ones per group in France.

This experiment took four years. Every year height and tree diameter was measured. Scientists examined also soil on the field to find if changed proportions of lignin components had influence on soil organisms After fourth year trees were harvested and their trunks analyzed for presence of different forms of lignin

Here are the results of this analysis: • We can see no significant difference between heignt or diameter between wild and transgenic trees • In 1996 French trees were on average higher than these in England as a result of climate difference.

Trees were also examined for presence of insects, fungi or bacteria. Theoretically trees with lower lignin level could be a better target for these pathogenes. However no statistically important differences were noticed.

However the rate of root decomposition was higher in case of transgenic trees. Their viability wasn’t impaired as a result of that but it may suggest that altered lignin is not such a good protection as natural one.

After a final harvest activity of COMT and CAD were measured. This was performed as scientists suspected that elder trees growing in natural environment can have higher activity than plants in greenhouse or in vitro cultures

Elder trees had elevated enzyme level but it was much lower among plants from transgenic lines.

Another part of experiment included analysis of lignin structure. Although none new chemical compounds appeared the proportion between components of cell walls should rapidly change. The technique used in that probe was called thioacidolysis. Two kinds of monomers guaiacyl (G) and Syringyl (S) were released by destabilization of beta-O-4 bonds in lignin structure. Analysis of their amount and percentage enabled preliminary lignin analysis

Normally elder trees has increased amount of beta-O-4 bonds but in case of transgenics ( especially ASOMT ) this number was significantly smaller.

The last and probably the most important part of the experiment was to assess the efficiency of pulping process. Method with NaOH was used during that experiment. Degree of delignification is described by parameter called kappa number. Researchers assumed that kappa number 25 is an optimal result Furthermore good pulp should have high degree of celluose polymerization (DP). The problem is the higer concentration of alkali the lower DP is.

Results show that ASCOMT wood needs more chemicals ~15% more alkali when ASCAD lines especially ASCAD21 gives serious savings.

Scientists claimed these results were very promising and suggested that ASCAD21 line should be consequently developed. However not all the people did share their enthusiasm... Greenpeace representants criticised the idea. Ecoactivists in UK attacked field where transgenic trees were planted and destroyed it...

This was of course an unjustified act of vandalism. But are • all the ecologists really cavemen idiots? • Some facts and questions: • There were only ten - twelve trees per group in the experiment. Is it enough number for reliable analysis? • The experiment lasted only four years. The youngest trees cut down for wood shouldn’t be younger than twenty years. In fact even forty - year - old trees are claimed to be too young for cutting down. • Twenty - year - old trees are much higher, heavier than four-year ones and their tissues have to face up with much more severe pressure. Is altered lignin able to give them sufficient protection?

Some facts and questions (II): • Root decomposition rate of transgenic trees was higher than of wild ones. It seemed not to affect their functioning. But elder trees have an enormous root area and increased degradation of them can be dangerous. Can they just fall down after strong wind or die as a result of impaired water absorption? • Elder trees are more prone to infections. Roots being damaged are perfect gates for incoming pathogenes. Four-year old poplars did not experience intensive pathogene invasion. But is it a reliable information? • Transgenic plants must be cultivated in ISOLATION. It means that these poplars were planted on isolated field far away from natural ecosystem they could „infect with transgenes”. So they probably didn’t have contact with wide spectrum of pests they could meet in their natural environment (forests ). They were attacked by these ones that just live in the local area.

Some facts and questions (III): • Two of three first co-authors of these paper work for Syngenta - biotech corporation engaged in plant bioengineering. Syngenta created transgenic rice which was not accepted for sale and was one of the main participants of Rice Genome Project. • To have a really reliable results we should have more trees and more ( about 30 years ) time. Do you think chairmen from commercial company will wait thirty years for results?

And if everything will be all right... Every year 25 000 square kilometres of Amazon jungle is being cut down. Let’s assume that it can cover worlds’ wood demand It means that every year we will need 25 000 square kiloetres covered with transgenic poplars

So we should talk not about transgenic trees but about trangenic forests • About monocultures created from a few plants and multiplied to terrifying number ? • Can such monoculture be stable? It can be the biggest monoculture ever created. Trees have more natural enemies than crops. Can they survive pest attack? And if not... Will we create new one having e.g additionally Bt-genes? Do we want such a brave new world?

There are many alternative solutions: 1. Pulp production using microroganism which degrade lignin. More expensive but more efficient than standard chemical procedure. It’s getting more and more popular. 2. Planting forests which are devoted for cutting down. In fact this procedure is practised in States and Canada. These forests are monocultures but they are more heterozygotic than trees derived from in vitro cultures and they do not contain transgenes. 3. Practising rational deforestation which doesn’t lead to erosion and enables forest to regenerate 4.And of course stop wasting paper. Global practising of that would be more beneficial for our forests than all the genetic experiments.

PULP (science) FICTION