Disease relevance of auxin

• A transferred DNA (T-DNA) tagging vector with the potential to produce dominant mutations was used with cocultured Agrobacterium tumefaciens and protoplasts to tag genes involved in the action of the plant growth substance auxin [1].
• The iaaL gene of Pseudomonas syringae, subspecies savastanoi, encodes an indoleacetic acid (IAA)-lysine synthetase [2].
• Ectopic expression of the wild-type Galpha-subunit phenocopies the Gbeta mutants (auxin hypersensitivity), probably by sequestering the Gbetagamma-subunits, whereas overexpression of Gbeta reduces auxin sensitivity and a constitutively active (Q222L) mutant Galpha behaves like the wild type [3].
• When grown on auxin amides, both etiolated and green tms2+ seedlings exhibit a variety of dose-dependent auxin toxicity effects. tms2 mRNA and the encoded amidohydrolase activity are both detectable in transgenic but not in wild-type seedlings, demonstrating that a cognate activity is lacking in wild-type Arabidopsis [4].
• An 11-bp element in D1, CCTCGTGTCTC, conferred auxin inducibility to a minimal cauliflower mosaic virus 35S promoter in transgenic tobacco seedlings as well as in carrot protoplasts (i.e., transient expression assays) [5].

High impact information on auxin

• PIN1 polar localization undergoes a dynamic rearrangement, which correlates with establishment of auxin gradients and primordium development [6].
• Our results demonstrate that GNOM is required for the recycling of auxin transport components and suggest that ARF-GEFs regulate specific endosomal trafficking pathways [7].
• Here, we characterize a novel member of the PIN family of putative auxin efflux carriers, Arabidopsis PIN4, that is localized in developing and mature root meristems [8].
• Regulation of auxin response by the protein kinase PINOID [9].
• Constitutive expression of PID causes a phenotype in both shoots and roots that is similar to that of auxin-insensitive plants, implying that PID, which encodes a serine-threonine protein kinase, negatively regulates auxin signaling [9].

Chemical compound and disease context of auxin

• Inactivation of auxin in tobacco transformed with the indoleacetic acid-lysine synthetase gene of Pseudomonas savastanoi [2].
• Occurrence of enzymes involved in biosynthesis of indole-3-acetic acid from indole-3-acetonitrile in plant-associated bacteria, Agrobacterium and Rhizobium [10].
• Nevertheless, the indole-3-pyruvate decarboxylase encoding ipdC gene is crucial in the overall IAA biosynthesis in Azospirillum [11].
• The PvACCase promoter was induced by wounding, Pseudomonas syringae infection, hydrogen peroxide, jasmonic acid (JA), ethylene, or auxin treatment [12].
• Transgenic tobacco plants co-expressing Agrobacterium iaa and ipt genes have wild-type hormone levels but display both auxin- and cytokinin-overproducing phenotypes [13].

Biological context of auxin

• Arabidopsis plants carrying mutations in the PINOID (PID) gene have a pleiotropic shoot phenotype that mimics that of plants grown on auxin transport inhibitors or of plants mutant for the auxin efflux carrier PINFORMED (PIN), with defects in the formation of cotyledons, flowers, and floral organs [9].
• Spatial patterns of expression of two immediate early auxin-responsive genes are altered in hookless1 mutants, suggesting that the ethylene response gene HOOKLESS1 controls differential cell growth by regulating auxin activity [14].
• An auxin response element displays a maximum in the Arabidopsis root and we investigate its developmental significance [15].
• The positive phototropism and the negative geotropism of grass seedling coleoptiles are believed to result from lateral movement of auxin from the irradiated to the shaded side and from the upper to the lower side, respectively [16].
• The plant hormone auxin has a central role in many aspects of plant growth and development [17].

Anatomical context of auxin

• In this issue of Cell, Geldner et al. demonstrate that the Arabidopsis ARF activator GNOM localizes to endosomes where it controls the polarized trafficking of the auxin efflux carrier PIN1 to the basal plasma membrane [18].
• Tobacco protoplasts treated with cAMP, or the adenylyl cyclase activator forskolin, no longer require auxin to divide [19].
• Here we used activation T-DNA tagging to create tobacco cell lines that can proliferate in the absence of the phytohormone auxin in the culture media [19].
• Auxin specifies stem cell niche formation by directly and indirectly affecting gene activities [20].
• We also show that auxin is necessary for GA-mediated control of root growth, and that attenuation of auxin transport or signalling delays the GA-induced disappearance of RGA from root cell nuclei [21].

Associations of auxin with other chemical compounds

• Indole-3-acetic acid, the major form of auxin in higher plants, is structurally similar to tryptophan and is a likely substrate for the AUX1 gene product [22].
• Genetic and physiological analyses suggest that the RHD3 gene is not required for proper cell type specification, and it is likely to act downstream of the hormones auxin and ethylene [23].
• Auxin biosynthesis by the YUCCA flavin monooxygenases controls the formation of floral organs and vascular tissues in Arabidopsis [24].
• We show here that NAC1, a new member of the NAC family, is induced by auxin and mediates auxin signaling to promote lateral root development [25].
• Trp-dependent auxin biosynthesis in Arabidopsis: involvement of cytochrome P450s CYP79B2 and CYP79B3 [26].

Gene context of auxin

• The AXR1 (auxin-resistant) protein, which has features of the ubiquitin-activating enzyme E1, is required for normal response to the plant hormone auxin in Arabidopsis thaliana [27].
• The ubiquitin-related protein RUB1 and auxin response in Arabidopsis [27].
• Chemical inhibitors of auxin transport change the intracellular localization of the auxin efflux carrier PIN1 in doc1/tir3 mutants, supporting the idea that BIG is required for normal auxin efflux [28].
• Further, overexpression of TIR1 promotes auxin response suggesting that SCFTIR1 is limiting for the response [29].
• The Arabidopsis BODENLOS gene encodes an auxin response protein inhibiting MONOPTEROS-mediated embryo patterning [30].

Analytical, diagnostic and therapeutic context of auxin

• Molecular cloning and structural analysis of a gene from Zea mays (L.) coding for a putative receptor for the plant hormone auxin [31].
• Extensive protein sequence analysis of the major auxin-binding protein allowed the construction of several synthetic oligonucleotide probes which were used to isolate a cDNA coding for this protein [31].
• We used in situ hybridization to localize two classes of auxin-regulated transcripts, GH3 and SAURs, within organs and tissues of soybean seedlings and flowers [32].
• Analysis by gas chromatography coupled to mass spectrometry indicated increased levels of both free and conjugated indole-3-acetic acid. sur1 was crossed to the mutant axr2 and the altered-auxin response mutant ctr1 [33].
• Sequence analysis of two peptide fragments showed total identity with the protein sequence of a strongly ripening-induced, auxin-dependent putative quinone oxidoreductase, Fragaria x ananassa quinone oxidoreductase (FaQR) [34].

References