Eucalyptus grandis has at least two functional SOC1-like floral activator genes

In a search for Eucalyptus grandis Hill ex Maiden MADS-box genes involved in floral initiation and development, we isolated two cDNAs (EgrMADS 3 and EgrMADS 4), which are functional orthologues of the Arabidopsis thaliana (L.) Heynh. floral activator gene SOC1. These two E. grandis genes are equally and most-actively expressed in vegetative tissues such as apical shoots and young leaves. The two genes are less actively, but differentially expressed in roots and unopened flowers. Ectopic expression of EgrMADS 3 or EgrMADS 4 in the late-flowering A. thaliana Ler soc1 (agl20) derivative complemented the phenotype of this mutant, and some of these transgenic lines flowered significantly earlier than the wild-type Ler ecotype. Overexpression of EgrMADS 3 or EgrMADS 4 in A. thaliana ecotype Columbia accelerated flowering time under short-day conditions. However, under the same conditions the flowering time of A. thaliana ecotype C24 was altered by the ectopic expression of EgrMADS 3, but not that of EgrMADS 4.The nucleotide sequence data reported will appear in the EMBL and GenBank Nucleotide Databases under the accession numbers AY263807 (EgrMADS 3) and AY263808 (EgrMADS 4).