Increasing cellulose content in wood of trees by altering the expression of genes involved in the lignin biosynthesis pathway seems not to be the optimal strategy because of possible undesired pleiotropic effects related to lignin reduction in transgenic trees. A possible approach to use cellulose biosynthesis genes has not, however, been tested so far. When aiming to modify the length of cellulose fibres, a promising approach was followed by over-expression of the gene GA20-oxidase encoding for the final step in the gibberellic acid biosynthesis pathway. To avoid possible pleiotropic effects during plant development the GA20-oxidase should be controlled by an inducible promoter, e.g. stem-specific one.
Acknowledgements. Thanks are due to Maria E. Eriksson for the 35S-GA20-oxidase construct. I want to thank Anke Schellhorn, Doris Ebbinghaus and O. Nowitzki for excellent technical assistance as well as the greenhouse staff for plant cultivation.
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