Genome-wide analysis of the auxin response factor gene family in cucumber

Auxin response factors (ARFs) participate in the transcriptional regulation of a series of biological processes related to growth and development. The ARF genes comprise a large multigene family in plants. Recently, a draft of the full cucumber (Cucumis sativus) genome assembly has been released; however, none of the ARF genes have been characterized. We made a comprehensive analysis of ARF genes in this species. Fifteen ARF genes were identified and could be divided into three classes. Intron presence and position were conserved to some extent within one phylogenetic group. Based on genome distribution analysis, tandem duplication appears to have contributed to ARF gene expansion. Specific motifs were selectively distributed among specific clades. Putative cis-elements involved in auxin response, light signaling responses, phytohormones, and defense responses were identified in promoter regions of the ARF genes. Almost all of the ARF genes exhibited a constitutive expression pattern, implying that there are functional redundancies among the ARF proteins.