Biomedical subjects

Zheng Qing Fu

Publications and source records attributed to Zheng Qing Fu.

5 recordsLinked to original sources

PubMed2006

Pseudomonas syringae HrpJ is a type III secreted protein that is required for plant pathogenesis, injection of effectors, and secretion of the HrpZ1 Harpin.

The bacterial plant pathogen Pseudomonas syringae requires a type III protein secretion system (TTSS) to cause disease. The P. syringae TTSS is encoded by the hrp-hrc gene cluster. One of the genes within this cluster, hrpJ, encodes a protein with weak similarity to YopN, a type III secreted protein from the animal pathogenic Yersinia species. Here, we show that HrpJ is secreted in culture and translocated into plant cells by the P. syringae pv. tomato DC3000 TTSS. A DC3000 hrpJ mutant, UNL140, was greatly reduced in its ability to cause disease symptoms and multiply in Arabidopsis thaliana. UNL140 exhibited a reduced ability to elicit a hypersensitive response (HR) in nonhost tobacco plants. UNL140 was unable to elicit an AvrRpt2- or AvrB1-dependent HR in A. thaliana but maintained its ability to secrete AvrB1 in culture via the TTSS. Additionally, UNL140 was defective in its ability to translocate the effectors AvrPto1, HopB1, and AvrPtoB. Type III secretion assays showed that UNL140 secreted HrpA1 and AvrPto1 but was unable to secrete HrpZ1, a protein that is normally secreted in culture in relatively large amounts, into culture supernatants. Taken together, our data indicate that HrpJ is a type III secreted protein that is important for pathogenicity and the translocation of effectors into plant cells. Based on the failure of UNL140 to secrete HrpZ1, HrpJ may play a role in controlling type III secretion, and in its absence, specific accessory proteins, like HrpZ1, may not be extracellularly localized, resulting in disabled translocation of effectors into plant cells.

Arabidopsis↗

PubMed2005

Three-dimensional model-free experimental error correction of protein crystal diffraction data with free-R test.

Experimental error correction and scaling is the last step in X-ray diffraction data processing. It is also critical in obtaining good-quality data. In this study, an algorithm is proposed to more generally and efficiently correct experimental error in X-ray crystal diffraction data. With this algorithm, the experimental error is represented by a symbolic three-dimensional function C(xi, eta, t) in the detecting space. Here, (xi, eta) are the coordinates of the diffraction spots on the image and t represents the data-collection time. While the theoretical form of C(xi, eta, t) is not known, it will be determined from the data through computer-aided analysis. The free R(merge) is introduced to check the validity of the solution. The three-dimensional symbolic function does not carry any assumptions and thus can generally account for experimental errors in various X-ray crystal diffraction experiments that are normally too complicated to be described by any fixed formula. Tests will be given to compare the results from different algorithms.

Algorithms↗

PubMed2005

SGXPro: a parallel workflow engine enabling optimization of program performance and automation of structure determination.

SGXPro consists of four components. (i) A parallel workflow engine that was designed to automatically manage communication between the different processes and build systematic searches of algorithm/program/parameter space to generate the best possible result for a given data set. This is performed by offering the user a palette of programs and techniques commonly used in X-ray structure determination in an environment that lets the user choose programs in a mix-and-match manner, without worrying about inter-program communication and file formats, during the structure-determination process. The current SGXPro program palette includes 3DSCALE, SHELXD, ISAS, SOLVE/RESOLVE, DM, SOLOMON, DMMULTI, BLAST, AMoRe, EPMR, XTALVIEW, ARP/wARP and MAID. (ii) A client/server architecture that allows the user to utilize the best computing facility available. (iii) Plug-in-and-play design, which allows easily integration of new programs into the system. (iv) User-friendly interface.

Crystallography, X-Ray↗

PubMed2004

The Pseudomonas syringae HopPtoV protein is secreted in culture and translocated into plant cells via the type III protein secretion system in a manner dependent on the ShcV type III chaperone.

The bacterial plant pathogen Pseudomonas syringae depends on a type III protein secretion system and the effector proteins that it translocates into plant cells to cause disease and to elicit the defense-associated hypersensitive response on resistant plants. The availability of the P. syringae pv. tomato DC3000 genome sequence has resulted in the identification of many novel effectors. We identified the hopPtoV effector gene on the basis of its location next to a candidate type III chaperone (TTC) gene, shcV, and within a pathogenicity island in the DC3000 chromosome. A DC3000 mutant lacking ShcV was unable to secrete detectable amounts of HopPtoV into culture supernatants or translocate HopPtoV into plant cells, based on an assay that tested whether HopPtoV-AvrRpt2 fusions were delivered into plant cells. Coimmunoprecipitation and Saccharomyces cerevisiae two-hybrid experiments showed that ShcV and HopPtoV interact directly with each other. The ShcV binding site was delimited to an N-terminal region of HopPtoV between amino acids 76 and 125 of the 391-residue full-length protein. Our results demonstrate that ShcV is a TTC for the HopPtoV effector. DC3000 overexpressing ShcV and HopPtoV and DC3000 mutants lacking either HopPtoV or both ShcV and HopPtoV were not significantly impaired in disease symptoms or bacterial multiplication in planta, suggesting that HopPtoV plays a subtle role in pathogenesis or that other effectors effectively mask the contribution of HopPtoV in plant pathogenesis.

Bacterial Proteins↗

PubMed2003

The Pseudomonas syringae type III-secreted protein HopPtoD2 possesses protein tyrosine phosphatase activity and suppresses programmed cell death in plants.

The bacterial plant pathogen Pseudomonas syringae possesses a type III protein secretion system that delivers many virulence proteins into plant cells. A subset of these proteins (called Avr proteins) is recognized by the plant's innate immune system and triggers defences. One defence-associated response is the hypersensitive response (HR), a programmed cell death (PCD) of plant tissue. We have previously identified HopPtoD2 as a type III secreted protein from P. s. pv. tomato DC3000. Sequence analysis revealed that an N-terminal domain shared homology with AvrPphD and a C-terminal domain was similar to protein tyrosine phosphatases (PTPs). We demonstrated that purified HopPtoD2 possessed PTP activity and this activity required a conserved catalytic Cys residue (Cys(378)). Interestingly, HopPtoD2 was capable of suppressing the HR elicited by an avirulent P. syringae strain on Nicotiana benthamiana. HopPtoD2 derivatives that lacked Cys(378) no longer suppressed the HR indicating that HR suppression required PTP activity. A constitutively active MAPK kinase, called NtMEK2DD, is capable of eliciting an HR-like cell death when transiently expressed in tobacco. When NtMEK2DD and HopPtoD2 were co-delivered into plant cells, the HR was suppressed indicating that HopPtoD2 acts downstream of NtMEK2DD. DC3000 hopPtoD2 mutants were slightly reduced in their ability to multiply in planta and displayed an enhanced ability to elicit an HR. The identification of HopPtoD2 as a PTP and a PCD suppressor suggests that the inactivation of MAPK pathways is a virulence strategy utilized by bacterial plant pathogens.

Apoptosis↗