Identification and characterization of homeobox genes in Eucalyptus

Abstract Homeobox genes encode transcriptional factors, usually involved in molecular control of plant developmentalpatterns. They can be divided into several classes according to conserved sequences within the homeobox regionand the presence of specific additional sequences. Based on these conserved sequences, we developed a searchprocedure to identify possible homeobox genes in the Eucalyptus Genome Sequencing Project Consortium(FORESTs) database. We were able to identify 50 Eucalyptus sequences (EST-contigs) containing thehomeodomainsequence.PhylogeneticanalysiswasappliedtothisESTs-contigsand44ofthemwerefoundtohavesimilarities with one of three well-known homeobox classes: Bell, Knox and HD-Zip, and their sub-classes. However,noEST-contiggroupedwiththefourthimportanthomeoboxclass,thePHD-fingerhomeobox.Ontheotherhand,twosequences have showed pronounced similarity to the Arabidopsis thaliana Wuschelgene, considered an “atypical”homeobox gene. Hierarchical clustering analysis of the expression pattern of these putative Eucalyptushomeoboxgenes revealed the presence of ten distinct expression groups. Combining phylogenetic analysis and expressionpatterns for some of the Eucalyptusgenes revealed interesting aspects about some of the potential homeoboxgenes, which might lead to a better understanding of the Eucalyptusbiology and to biotechnological applications.