The family of Dof transcription factors in pine
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The Dof proteins are members of a major family of plant transcription factors that contain a single C2/C2 class of zinc-finger DNA-binding domain. The size of gene families and the role of transcription factors in trees have only been partially addressed. We studied the size and structure of the Dof gene family in loblolly and maritime pines. The presence of the conserved Dof domain was a typical feature in the ten Dof genes identified in both pine species. Three of the genes lack intron structures and the other seven have a single intron. An analysis of putative cis elements in the promoter region of the genes suggests that the members of the family play different roles throughout the life cycle of the trees in a way that is unrelated to the subfamily to which they belong. Using the information available in the maritime pine database, we have cloned the corresponding open reading frames and initiated structural and functional studies. The gene expression of maritime pine Dof factors was examined at different developmental stages: from embryo to adult tree. This study has revealed a differential pattern of gene expression based on developmental stage and tissue specificity. The interaction both in vitro and in vivo between Dof factors has been addressed and our data showed a negative effect of Dof 2 in the Dof 5-regulated expression of a target gene in maritime pine. These findings suggest that both genes interact in the regulation of gene expression.