Tiryaki Iskender, Staswick Paul E
Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE 68583-0915, USA.
Plant Physiol. 2002 Oct;130(2):887-94. doi: 10.1104/pp.005272.
A screen for Arabidopsis mutants that were insensitive to methyl jasmonate (MeJA) in an assay for seedling root growth yielded only alleles of previously isolated mutants jar1 and coi1, with one exception. Mapping of the locus and morphological characterization of the new mutant suggested it might be allelic to axr1, which had not previously been reported to show resistance to MeJA. The F(1) from a cross of the new mutant with axr1-3 did not show complementation, confirming that these are the same genes. The new allele is called axr1-24. In addition to MeJA and indole-3-acetic acid (IAA), axr1-24 had decreased sensitivity to 1-aminocyclopropane-1-carboxylic acid, 6-benzylamino-purine, epi-brassinolide, and abscisic acid. Both axr1-24 and the previously characterized axr1-3 allele were shown to be susceptible to the opportunistic pathogen Pythium irregulare, a trait found in other jasmonate response mutants, including jar1-1. The double mutant jar1-1/axr1-3 was more resistant to inhibition of root growth by MeJA and was more susceptible to P. irregulare infection than either single mutant, suggesting these genes might act in independent response pathways. In contrast, resistance to IAA in the double mutant was not different from axr1-3. Northern-blot analysis showed that IAA induced the jasmonate-responsive lipoxygenase 2, AOS, and AtVSP gene transcripts and induction was strongly impaired in axr1-3. However, transcript induction by MeJA was only minimally affected in axr1-3. 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.
通过检测幼苗根系生长来筛选对茉莉酸甲酯（MeJA）不敏感的拟南芥突变体，结果除一个例外，只得到了先前分离出的突变体jar1和coi1的等位基因。对新突变体的基因座进行定位并对其形态特征进行分析，结果表明它可能与axr1等位，此前尚未报道axr1对MeJA有抗性。新突变体与axr1 - 3杂交产生的F(1)代未表现出互补现象，证实它们是相同的基因。这个新的等位基因被称为axr1 - 24。除了MeJA和吲哚 - 3 - 乙酸（IAA）外，axr1 - 24对1 - 氨基环丙烷 - 1 - 羧酸、6 - 苄基氨基嘌呤、表油菜素内酯和脱落酸的敏感性也降低。axr1 - 24和先前鉴定的axr1 - 3等位基因都对机会性病原菌不规则腐霉敏感，这一特性在包括jar1 - 1在内的其他茉莉酸反应突变体中也有发现。双突变体jar1 - 1/axr1 - 3对MeJA抑制根系生长的抗性更强，且比任何一个单突变体更易受不规则腐霉感染，这表明这些基因可能在独立的反应途径中起作用。相比之下，双突变体对IAA的抗性与axr1 - 3没有差异。Northern杂交分析表明，IAA诱导了茉莉酸反应性脂氧合酶2、AOS和AtVSP基因转录本，而axr1 - 3中这种诱导作用严重受损。然而，axr1 - 3中MeJA诱导的转录本仅受到轻微影响。这项研究表明，除了生长素信号传导外，AXR1基因座还参与MeJA反应，为茉莉酸和生长素信号传导途径之间提供了一个机制联系。
