Abstract:
Auxin is a central hormone involved in a wide range of developmental processes including the specification of vascular
stem cells. Auxin Response Factors (ARF) are important actors of the auxin signalling pathway, regulating the transcription
of auxin-responsive genes through direct binding to their promoters. The recent availability of the Eucalyptus grandis
genome sequence allowed us to examine the characteristics and evolutionary history of this gene family in a woody plant of
high economic importance. With 17 members, the E. grandis ARF gene family is slightly contracted, as compared to those of
most angiosperms studied hitherto, lacking traces of duplication events. In silico analysis of alternative transcripts and gene
truncation suggested that these two mechanisms were preeminent in shaping the functional diversity of the ARF family in
Eucalyptus. Comparative phylogenetic analyses with genomes of other taxonomic lineages revealed the presence of a new
ARF clade found preferentially in woody and/or perennial plants. High-throughput expression profiling among different
organs and tissues and in response to environmental cues highlighted genes expressed in vascular cambium and/or
developing xylem, responding dynamically to various environmental stimuli. Finally, this study allowed identification of
three ARF candidates potentially involved in the auxin-regulated transcriptional program underlying wood formation.
