Browsing by Subject "Pseudomonas syringae"
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Item An in vitro evaluation of a Pseudomonas Syringae pv. Tagetis strain as a potential biocontrol agent(Texas Tech University, 1997-12) Krieg, AndreaThe potential of SL Pseudomonas syringae pv. tageris Tox strain to provide control of the Tox* strain was tested using competition as a basis for comparison. Initially, growth curves of individual strains in both complex and defined media were developed In the complex medium 523, the Tox strain did exhibit greater growth than the other two strains tested and was significantly greater at two points during the assay. In all othCT media tested, the growth of the three strains was almost identical. Ratios of the Tox to Tox*/Rif strains -1:1 and 3:1, WCTC then tested in minimal salts (defined) and 523 (complex) media. In the defined medium, the ratio began and ended at the same point, either 1:1 or 3:1. In the complex medium, only the 1:1 ratio was tested and this ended in a 4:1 ratio in favor of the Tox strain. The 3:1 ratio as well as individual strains were then tested using sunflowCT leaf disks. The Tox and Tox*/Rif strains alone grew much faster than the Tox' strain in the ratio, while the Tox^/Rif strain grew almost as well as it did inoculated as a single strain. The ratio behaved in contradiction of the behavior obsoved in culture. The Tox strain seemed to be inhibited in the ratio and the data taken at 48 hours was 1:5 in fiavor of the Tox*/Rif strain. While still contradicting the results obtained in culture media, the whde plant assay did not follow the same pattern as that seen in the leaf disk assay. At 24 hours, the ratio between the Tox and Tox^/Rif strains which began at 3:1, had shnmk to a little more than 1:1. Data taken at 48 hours showed that the Tox^/Rif strain's population had outgrown that of the Tox' strain reversing the ratio to 1:1.4. From the data presented, it can not be concluded that the Tox strain is capable of providing any measure of biological control of the Tox*/Rif strain.Item Bacterial Effector HopF2 Suppresses Arabidopsis Immunity by Targeting BAK1(2013-07-19) Zhou, JinggengPseudomonas syringae delivers a plethora of effector proteins into host cells to sabotage host immune responses and physiology to favor infection. We have previously shown that P. syringae pv. tomato DC3000 effector HopF2 suppresses Arabidopsis innate immunity triggered by multiple pathogen-associated molecular patterns (PAMP) at the plasma membrane. We show here that HopF2 possesses distinct mechanisms in the suppression of two branches of PAMP-activated MAP kinase cascades. In contrast to blocking MKK5 in MEKK1-MKK4/5-MPK3/6 cascade, HopF2 targets additional component(s) upstream of MEKK1 in MEKK1-MKK1/2-MPK4 cascade and plasma membrane-localized receptor-like cytoplasmic kinase BIK1 and its homologs. We further show that HopF2 directly targets BAK1, a plasma membrane-localized receptor-like kinase involved in multiple PAMP signaling. The interaction between BAK1 and HopF2 or two additional P. syringae effectors AvrPto and AvrPtoB, was confirmed in vivo and in vitro. Consistent with BAK1 as a physiological target of HopF2, the lethality of overexpression of HopF2 in wild-type Arabidopsis transgenic plants was largely alleviated in bak1 mutant plants. Identification of BAK1 as an additional HopF2 virulence target not only explains HopF2 suppression of multiple PAMP signaling at the plasma membrane, but also supports the notion that pathogen virulence effectors have multiple targets in host cells.Item Characterization of salA, syrF, and syrG Regulatory Networks Involved in Plant Pathogenesis by Pseudomonas syringae pv. syringae B728a(2014-02-06) Vaughn, Vanessa LynnPseudomonas syringae pv. syringae B728a, causal agent of brown spot on bean, is an economically important plant pathogen that utilizes extracellular signaling to initiate a lifestyle change from an epiphyte to a pathogen. LuxR regulatory proteins play an important role in the transcriptional regulation of a variety of biological processes involving two-component signaling, quorum sensing, and secondary metabolism. Analysis of the B728a genome identified 24 LuxR-like proteins, three of which are salA, syrF, and syrG located adjacent to the syringomycin gene cluster. All three proteins exhibit domain architecture that placed these LuxR-like proteins into a subfamily of LuxR?s associated with regulation of secondary metabolism in Pss B728a. The transcriptional start sites of salA, syrG, and syrF were located 63, 235, and 498 bp upstream of the start codons, respectively, using primer extension analysis. The predicted -10/-35 promoter region of syrF and syrG was confirmed using site-directed mutagenesis and GFP reporters that showed there were conserved promoter sequences observed around the -35 promoter region. It has been established that SalA binds to the promoter of syrF, therefore these conserved promoter sequences serve as the putative binding site for SalA. Deletion mutants of salA, syrF, and syrG failed to produce syringomycin and displayed reduction of virulence on bean. QRT-PCR analysis results revealed that both syrG and syrF are highly expressed in the apoplast indicating that they encode important transcriptional regulators of genes critical to the plant-pathogen interaction. Additionally, this report showed that syrG and syrF are important transcriptional regulators of syringomycin biosynthesis genes, but are not involved in the regulation of virulence genes that reside outside of the syr-syp gene cluster. Overexpression analysis and GFP reporters identified SyrG as an upstream transcriptional activator of syrF, where both SyrG and SyrF activate promoters of syringomycin biosynthesis genes. This study demonstrates that the interaction between SalA, SyrG, and SyrF for the regulation of syringomycin is complex requiring further investigation.Item Optimizing control of woollyleaf bursage (Ambrosia grayi (A. Nels) Shinners) with Pseudomonas syringae pv. tagetis(Texas Tech University, 1999-12) Sheikh, TehminaNOT AVAILABLE.