Jakob Katrin, Kniskern Joel M, Bergelson Joy
Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago 60637, USA.
Mol Plant Microbe Interact. 2007 Feb;20(2):146-58. doi: 10.1094/MPMI-20-2-0146.
Pseudomonas viridiflava is a common pathogen of Arabidopsis thaliana in wild populations, yet very little is known about mechanisms of resistance and virulence in this interaction. We examined the induced defense response of A. thaliana to several strains of P. viridiflava collected from this host by quantifying the expression of PR-1 and LOX2/PDF1.2, which serve as markers for induction of the salicylic and jasmonic acid (JA) pathways, respectively. Growth of these strains then was assessed on Col-0, the fad3/7/8 and coil-1 mutants deficient in JA- and ethylene (ET)-induced defense responses, and the sid2-1 mutant deficient in salicylic acid-induced defense responses. All strains of P. viridiflava induced high expression of LOX2 and PDF1.2 on Col-0. In contrast, PR-1 expression was delayed and reduced relative to PDF1.2 expression. Additionally, three of four P. viridiflava strains were more virulent on fad3/7/8 relative to Col-0, whereas all strains were more virulent on coil-1 relative to Col-0, indicating that P. viridiflava generally may be suppressed by JA/ET-mediated defense responses. In contrast, no increase in the growth of P. viridiflava strains was observed in the sid2-1 mutant relative to Col-0. Parallel experiments were performed with the closely related P. syringae pv. tomato for comparative purposes. In addition, we assessed the role of pectate lyase and the alternative sigma factor HrpL in P. viridiflava virulence on A. thaliana and found that pectate lyase activity is correlated with virulence, whereas the removal of pectate lyase or HrpL significantly reduced virulence.
绿黄假单胞菌是野生拟南芥种群中的常见病原体，但对于这种相互作用中的抗性和毒力机制知之甚少。我们通过量化PR-1和LOX2/PDF1.2的表达，研究了拟南芥对从该宿主分离的几种绿黄假单胞菌菌株的诱导防御反应，PR-1和LOX2/PDF1.2分别作为水杨酸和茉莉酸（JA）途径诱导的标志物。然后在Col-0、缺乏JA和乙烯（ET）诱导防御反应的fad3/7/8和coil-1突变体以及缺乏水杨酸诱导防御反应的sid2-1突变体上评估这些菌株的生长情况。所有绿黄假单胞菌菌株在Col-0上均诱导LOX2和PDF1.2的高表达。相比之下，PR-1的表达相对于PDF1.2的表达延迟且降低。此外，相对于Col-0，四株绿黄假单胞菌中的三株在fad3/7/8上的毒力更强，而相对于Col-0，所有菌株在coil-1上的毒力更强，这表明绿黄假单胞菌通常可能受到JA/ET介导的防御反应的抑制。相比之下，相对于Col-0，在sid2-1突变体中未观察到绿黄假单胞菌菌株生长的增加。为了进行比较，用密切相关的丁香假单胞菌番茄致病变种进行了平行实验。此外，我们评估了果胶酸裂解酶和替代σ因子HrpL在绿黄假单胞菌对拟南芥毒力中的作用，发现果胶酸裂解酶活性与毒力相关，而去除果胶酸裂解酶或HrpL会显著降低毒力。
