High impact information on AXR1

• One of these genes, AXR1, is defined by recessive mutations that confer auxin resistance to the roots, rosettes and inflorescences of mutant plants [1].
• Arabidopsis auxin-resistance gene AXR1 encodes a protein related to ubiquitin-activating enzyme E1 [1].
• The AXR1 protein is highly diverged from previously characterized E1 enzymes, however, and lacks a key cysteine residue that is essential for E1 activity [1].
• Extracts from mutant seedlings lacking AXR1 did not promote formation of the RUB-ECR1 thiolester, indicating that AXR1 is the major activity in this tissue [2].
• Further, mutations in TIR1 display a synergistic interaction with mutations in AXR1, suggesting that the two genes function in overlapping pathways [3].

Biological context of AXR1

• Most strikingly, plants deficient in both RCE1 and AXR1 have an embryonic phenotype similar to mp and bdl mutants, previously shown to be deficient in auxin signaling [4].
• The expression of AXR1 and ECR1 is restricted to zones of active cell division and cell elongation, consistent with their role in growth regulation [5].
• Mutations in the AXR1 gene result in a reduction in auxin response and diverse defects in auxin-regulated growth and development [5].
• These results suggest that ARGOS may transduce auxin signals downstream of AXR1 to regulate cell proliferation and organ growth through ANT during organogenesis [6].
• RESULTS: Here we show that the resistance of max mutant buds to apically supplied auxin is largely independent of the known, AXR1-mediated, auxin signal transduction pathway [7].

Anatomical context of AXR1

• In addition, bdl seedlings were insensitive to the auxin analogue 2,4-D, as determined by comparison with auxin resistant1 (axr1) seedlings. bdl embryos deviated from normal development as early as the two-cell stage at which the apical daughter cell of the zygote had divided horizontally instead of vertically [8].

Associations of AXR1 with chemical compounds

• 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 [2].
• This study demonstrates that in addition to auxin signaling, the AXR1 locus is involved in MeJA response, providing a mechanistic link between jasmonate and auxin-signaling pathways [9].
• Surprisingly, two loss-of-function mutants at the AXR1 locus (axr1-3 and axr1-12) were hypersensitive to l-glutamate [10].
• Both sar1 and sar3 mutations affect the localization of the transcriptional repressor AXR3/INDOLE ACETIC ACID17, providing a likely explanation for suppression of the phenotype conferred by axr1 [11].

Other interactions of AXR1

• Furthermore, we show that the AtCUL1 component of SCF(COI1) complexes is modified in planta, where mutations in AXR1 decrease the abundance of the modified AtCUL1 of SCF(COI1) and lead to a reduction in JA response [12].
• The SAR1 gene of Arabidopsis acts downstream of the AXR1 gene in auxin response [13].
• However, the morphology of double mutant plants indicates that there is an inter-action between the AXR1 and AUX1 genes [14].
• Acceleration of Aux/IAA proteolysis is specific for auxin and independent of AXR1 [15].

Analytical, diagnostic and therapeutic context of AXR1

• In order to detect gene products involved in Arabidopsis drought adaptive strategy, 2D-PAGE protein patterns of two auxin-insensitive mutants, axr1, axr2, differentially affected in specific drought responses, were compared to the wild-type Columbia ecotype, in well-watered and drought-stressed conditions [16].

References