The objective of this project is the transformation of selected plants with antisense genes which interfere with the different steps of lignin synthesis in order to reduce the lignin content and to modify its monomeric composition.
The negative effects of lignins on the digestibility of forage crops and other edible plants are well established. Taking into account the large variations in lignin content encountered in nature even for one plant, as well as the natural chemical diversity of lignins, it seems possible to design plants with a modified lignin content more adapted to specific agricultural and industrial uses. For a long time, this objective has interested plant breeders who have tried through conventional genetics to get forage crops, such as maize, with a reduced lignin content. The same goal can now be reached by plant genetic engineering and particularly by the use of the antisense ribonucleic acid (RNA) approach. In relation to forage digestibility the project has been focused on the improvement of alfalfa and tall fescue, perennial species characterized by productivity and hardiness, but exhibiting a low level of palatibility and digestibility.
The objective of this project is the transformation of selected plants with antisense genes which interfere with the different steps of lignin synthesis, to reduce the lignin content and to modify its monomeric composition.
Lignins are the second most abundant compounds in the biosphere after cellulose and represent 20% of the total organic carbon. Their negative effects on the quality of forage crops and other edible plants is well established and it has been long known that lignins are one of the prime factors of forage indigestibility in cattle. In addition lignins are waste components in the pulp industry since they have to be removed from wood to obtain the chemical pulp necessary for papermaking. In Europe millions of tons of soluble lignin derivatives are prduced every year. They are poorly utilised substances and their extraction, which is the cause of a lot of pollution, is a highly expensive process.
The content and chemical diversity of lignin in plants varies according to the species, the environmental conditions, and the specific cultivar. For a long time, plant breeders have tried through conventional genetics to design plants with a reduced and modified lignin content more adapted to specific agricultural and industrial uses. This project uses a plant genetic engineering approach to achieve the same objective but employing antisense RNA technology in the down regulation of three genes coding for enzymes involved in the lignification process; O. methyltransferase (OMT) which controls the methylation content of lignins, and cinnamoyl COA reductase (CCR), and cinnamyl alcohol dehydrogenase (CAD) both specific enzymes of lignin monomer synthesis which control the flux of lignin production. The experiments will be conducted on model plants (tobacco, bean) and will then be extended to target plants of economic interest : forages (alfalfa and tall fescue), and woody plants (poplar and eucalypt). They will allow specific modification of lignin content without alteration of other traits, providing advantages in terms of the time and specificity, in comparison with manipulation by classical breeding methods.
The project will be based on the following approach :
a) Characterization of genes involved in lignification
b) Transformation of model and target plants
c) Molecular, chemical and cytological analysis of transformed plants d) Studies on digestibility (indigestibility) of modified forage crops and on technological properties of transformed woody plants in relation with pulp production
e) Cultivation on a large scale of the transformants and field trials for testing their agronomical properties
Funding SchemeCSC - Cost-sharing contracts
SW1P 3JF London