Expression responses of ARFs to abiotic stress also has been identified in banana. In tea plants, the expression of several CsARFs significantly changed under salt and dehydration stresses. Expression profiling using qRT-PCR and microarray data revealed many water stress-responsive ARF genes in soybeans. Another ARF, OsARF12, is also involved in phosphate homeostasis. In rice, OsARF16 is required for iron and phosphate starvation responses. Recent studies have uncovered the involvement of ARFs in responses to environmental stress. The genome-wide identification and expression analysis of ARF genes in tomato also indicated that ARF genes may play diverse roles during the reproductive developmental stages in Solanaceae in general. This suggests that AtARF7 and AtARF19 play essential roles in auxin mediated plant development by regulating both unique and partially overlapping sets of target genes. Another double mutant, AtARF7/ AtARF19, has a strong auxin-related phenotype, resulting in severely impaired lateral root formation and abnormal gravitropism in both hypocotyls and roots. The AtARF6/ AtARF8 double mutant flowers are presented as infertile closed buds with short petals, short stamen filaments, undehiscent anthers and immature gynoecia, indicating that the AtARF6 and AtARF8 gene dosage quantitatively affects the timing of flower maturation. The AtARF2 gene regulates leaf senescence and floral organ abscission independently of the ethylene and cytokinin response pathways, and the AtARF1/ ATARF2 double mutant enhanced many AtARF2 phenotypes. Furthermore, studies of double mutants of the AtARF genes provide insight into their overlapping functions. A T-DNA insertion mutant in ATARF8 was reported to control reproductive organ development by uncoupling fertilization and pollination from fruit development. A mutation in the AtARF7 gene blocks the hypocotyl response to blue light and auxin stimuli, and shows differential growth in aerial tissues. The abnormal formation of vascular strands and the embryo axis are observed in the mutant AtARF5. Another mutant, AtARF3, displays deviant floral meristem and reproductive organs. In Arabidopsis, an ARF2 loss-of-function mutant shows severe leaf senescence and floral organ abscission. In the past years, several ARF gene mutants were screened to investigate the genes’ genetic functions. A typical ARF protein consists of three conserved domains: a plant specific B3-like DNA-binding domain (DBD) at the N-terminus, an activation domain (AD) or repression domain (RD) in the middle region, and a conserved C-terminal dimerization domain (CTD). Auxin response factor (ARF) proteins, an essential component of the auxin signaling pathway, regulate the expression levels of auxin response genes by targeting the auxin response elements (AuxREs) on their promoters. In plants, auxin signaling is transmitted by transcriptional regulation of some auxin early responsive gene families, such as Auxin/Indole-3-acetic acid (Aux/IAA), Gretchen Hagen3 (GH3) and Small Auxin Up RNA (SAUR). Phytohormones play pivotal roles in the various aspects of plant growth and development, including embryogenesis, organogenesis, root architecture, flower and fruit development, tissue and organ patterning, vascular development, and secondary metabolism. Since auxin and ARF genes have been identified in many plant species, our data is imperative to reveal the function of ARF mediated auxin signaling in the adaptation to the challenging Dendrobium environment. Based on our data, several hormones and significant stress responsive DnARF genes have been identified. To uncover the basic information of DnARF gene responses to abiotic stresses, we analyzed their expression patterns under various hormones and abiotic treatments. #Calculate pi of amino acid in the middle of a polypeptide Activator#Our data showed that DnARF6 is a transcriptional activator in Dendrobium officinale. Furthermore, the transcription activation abilities of DnARF1, DnARF4, and DnARF6 were tested in a yeast system. Three selected DnARFs, including DnARF1, DnARF4, and DnARF6, were confirmed to be nuclear proteins according to their transient expression in epidermal cells of Nicotiana benthamiana leaves. Using our latest public Dendrobium transcriptomes, a comprehensive characterization and analysis of 14 DnARF genes were performed. Auxin response factor (ARF) proteins play roles in plant responses to diverse environmental stresses by binding specifically to the auxin response element in the promoters of target genes.
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