Eucalyptus event H421 was produced by Agrobacterium tumefaciens-mediated transformation.

The T-DNA of the transformation vector pBI121 is constituted of two expression cassettes:

• the coding sequence of gene nptII from Escherichia coli
• the coding sequence of cel1 from Arabidopsis thaliana, which codes for expression of enzyme β-1,4 endoglucanase (Cel1), a glycosyl hydrolase that links to non-crystalline cellulose and xyloglucans promoting relaxation of cell walls during the phases of expansion and elongation of the plant cell.

Molecular analysis (Southern blot, sequencing and PCR) showed that a single functional copy of cel1 and nptII expression cassettes has been inserted in a single locus of the eucalyptus genome. Sequencing of event H421 confirmed that constructs present in the vector were preserved in the transformation process and that neither gene disruption nor structure disruption of the parental eucalyptus genome expression occured.