Explosive tandem and segmental duplications of multigenic families in Eucalyptus grandis

Abstract

Plant organisms contain a large number of genes belonging to numerous multigenic families whose evolution size reflects some functional constraints. Sequences from eight multigenic families, involved in biotic and abiotic responses, have been analyzed in Eucalyptus grandis and comparedwithArabidopsis thaliana. Two transcription factor families APETALA 2 (AP2)/ethylene responsive factor and GRAS, two auxin transporter families PIN-FORMED and AUX/LAX, two oxidoreductase families (ascorbate peroxidases [APx] and Class III peroxidases [CIII Prx]), and twofamilies of protectivemolecules late embryogenesis abundant (LEA) andDNAjwere annotated in expert and exhaustive manner. Many recent tandem duplications leading to the emergence of species-specific gene clusters and the explosion of the gene numbers have been observed for the AP2, GRAS, LEA, PIN, and CIII Prx in E. grandis,while the APx, the AUX/LAX and DNAj are conserved between species. Although no direct evidence has yet demonstrated the roles of these recent duplicated genes observed in E. grandis, this could indicate their putative implications in themorphological and physiological characteristicsof E. grandis,andbe thekey factor for thesurvival of thisnondormant species.Global analysisof key familieswouldbe a good criterion to evaluate the capabilities of some organisms to adapt to environmental variations.