Ritter C, Dangl J L
Max-Delbrück Laboratory, Köln, Germany.
Mol Plant Microbe Interact. 1995 May-Jun;8(3):444-53. doi: 10.1094/mpmi-8-0444.
We demonstrate that the avirulence gene avrRpm1, isolated from Pseudomonas syringae pv. maculicola strain Psm M2 via interaction with the Arabidopsis resistance gene RPM1, is also required for maximal virulence on this host. Two avrRpm1::Tn3-Spice marker-exchange mutants do not elicit a hypersensitive reaction on RPM1-containing Arabidopsis accessions Col-0 and Oy-0. Surprisingly, these mutants neither generate disease symptoms, nor grow in planta, after inoculation onto susceptible accessions Nd-0, Fe-1, and Mt-0. These deficiencies can be corrected in a merodiploid containing a wild-type avrRpm1 allele, and are not observed following gene-replacement with avrRpm1::Tn3-Spice alleles containing insertions just beyond the 3' terminus of the avirulence gene open reading frame. AvrRpm1 mRNA is expressed in low, but detectable amounts, in rich media. Induced accumulation of transcript is observed 3 h after shift to minimal media, and an avrRpm1::Tn3-Spice marker-exchanged reporter gene reaches maximal induction 30 min after shift. AvrRpm1 transcription starts 5 base-pairs 3' of the putative regulatory "hrp-box" cis-element found upstream of many P. syringae avr and hrp genes. Transcriptional induction of the marker-exchanged reporter gene in minimal media is enhanced by a carbon source. Induction in planta is the same in either resistant or susceptible Arabidopsis accessions, and is unaffected by the presence or absence of wild-type avrRpm1. As previously observed for many other P. syringae avr genes, transcriptional regulation of avrRpm1 in minimal media is dependent on hrpL and hrpS.
我们证明，通过与拟南芥抗性基因RPM1相互作用从丁香假单胞菌番茄致病变种菌株Psm M2中分离出的无毒基因avrRpm1，也是该宿主最大毒力所必需的。两个avrRpm1::Tn3-Spice标记交换突变体在含有RPM1的拟南芥种质Col-0和Oy-0上不会引发超敏反应。令人惊讶的是，接种到易感种质Nd-0、Fe-1和Mt-0上后，这些突变体既不产生疾病症状，也不在植物体内生长。这些缺陷可以在含有野生型avrRpm1等位基因的部分二倍体中得到纠正，并且在用无毒基因开放阅读框3'末端之外含有插入片段的avrRpm1::Tn3-Spice等位基因进行基因替换后未观察到这些缺陷。AvrRpm1 mRNA在丰富培养基中以低但可检测的量表达。转移到基本培养基3小时后观察到转录本的诱导积累，并且一个avrRpm1::Tn3-Spice标记交换报告基因在转移后30分钟达到最大诱导。AvrRpm1转录起始于许多丁香假单胞菌avr和hrp基因上游发现的假定调控“hrp-box”顺式元件的3'端5个碱基对处。基本培养基中标记交换报告基因的转录诱导因碳源而增强。在抗性或易感拟南芥种质中植物体内的诱导是相同的，并且不受野生型avrRpm1存在与否的影响。如先前对许多其他丁香假单胞菌avr基因所观察到的，avrRpm1在基本培养基中的转录调控依赖于hrpL和hrpS。
