Genetic Variation and Genetical Control of Growth and Flowering in Woody Plants: Molecular Techniques

A genetically modified (GM) poplar (Populusnigra) that overexpresses a key enzyme in the plant hormone gibberellin (GA) synthesis system was produced by the Agrobacterium method. Gibberellin is known to control the elongation and growth of higher plants. GA20-oxidase is a key enzyme in the biosynthesis of active GAs. The major gibberellin biosynthetic pathway involving the participation of GA20-oxidase is shown and described along with other genes and enzymes like GA20ox, GA3ox, GA 3beta-hydroxylase, GA2ox, and GA 2beta-hydroxylase. There are six clades in the GA oxidase gene subfamily. In this chapter, the production of genetically modified (GM) poplar overexpressing a known tobacco GA 20-oxidase gene, NtGA20ox and a poplar gene PnGA20ox, classified under the same GA 20-oxidase gene, is described. This genetic variant and recombinant poplar showed enhanced above-ground growth and stem biomass production. In addition, GM poplars with altered expression of genes controlling flower bud formation. This successfully reduced the long juvenile phase period to less than one year. Genetic modification has made it possible to control tree growth and reproduction.