Xanthomonas axonopodis pv. punicae （Xap） causing bacterial blight is an important pathogen that incurs significant losses to the exportability of pomegranate. Xap uses the Xop TTSS-effector, via the type three secre...Xanthomonas axonopodis pv. punicae （Xap） causing bacterial blight is an important pathogen that incurs significant losses to the exportability of pomegranate. Xap uses the Xop TTSS-effector, via the type three secretion system, to suppress pomegranate immunity. Here, we investigate the role of XopL during blight pathogenesis. We observed that XopL is essential for its in planta growth and full virulence. Leaves inoculated with Xap AxopL produced restricted water-soaked lesions compared to those inoculated with wild-type Xap. XopL supports Xap for its sustained multiplication in pomegranate by suppress- ing the plant cell death （PCD） event. We further demon- strated that XopL suppresses immune responses, such as callose deposition and production of reactive oxygen species （ROS）. RT-qPCR analysis revealed that immune responsive genes were upregulated when challenged with Xap AxopL, whereas upregulation of such genes was compromised in the complemented strain containing the xopL gene. The transiently expressed XopL：：EYFP fusion protein was local- ized to the plasma membrane, indicating the possible site of its action. Altogether, this study highlights that XopL is an important TTSS-effector of Xap that suppresses plant immune responses, including PCD, presumably to support the multiplication of Xap for a sufficient time-period during blight disease development.展开更多
Plant pathogenic bacteria engage in an ongoing struggle for survival.Gram negative phytopathogenic prokaryotes deploy typeⅢsecretion system to deliver effector proteins into plant cells to manipulate the host cellula...Plant pathogenic bacteria engage in an ongoing struggle for survival.Gram negative phytopathogenic prokaryotes deploy typeⅢsecretion system to deliver effector proteins into plant cells to manipulate the host cellular environment.In many cases,the targets of these effector proteins are unknown.The bacterial blight pathogen,Xanthomonas oryzae pv.oryzae(Xoo),causes a devastating disease in rice and the Xoo-rice interaction is an example of the ongoing evolutionary battle between plants and pathogens.In this study,we show that an effector XopL from Xoo exhibits E3 ubiquitin ligase activity and induces cell death in the nonhost Nicotiana benthamiana(Nb).Through yeast two-hybrid,co-immunoprecipitation,and biomolecular fluorescence complementation assays,it was shown that XopL interacts with ferredoxin(NbFd),an electron transport molecule in plant chloroplasts.XopL induced defense-related response in Nb and specifically targeted NbFd for ubiquitination and ubiquitin-mediated degradation,a process that increased the production of reactive oxygen species(ROS).This study demonstrates the ubiquitination and degradation of NbFd as a result of XopL activity,which further illustrates the tremendous functional diversity in Xanthomonas effector proteins.展开更多
基金supported by DBT grant (No. BT/PR8871/PBD/16/1052/2013), Govt of India
文摘Xanthomonas axonopodis pv. punicae （Xap） causing bacterial blight is an important pathogen that incurs significant losses to the exportability of pomegranate. Xap uses the Xop TTSS-effector, via the type three secretion system, to suppress pomegranate immunity. Here, we investigate the role of XopL during blight pathogenesis. We observed that XopL is essential for its in planta growth and full virulence. Leaves inoculated with Xap AxopL produced restricted water-soaked lesions compared to those inoculated with wild-type Xap. XopL supports Xap for its sustained multiplication in pomegranate by suppress- ing the plant cell death （PCD） event. We further demon- strated that XopL suppresses immune responses, such as callose deposition and production of reactive oxygen species （ROS）. RT-qPCR analysis revealed that immune responsive genes were upregulated when challenged with Xap AxopL, whereas upregulation of such genes was compromised in the complemented strain containing the xopL gene. The transiently expressed XopL：：EYFP fusion protein was local- ized to the plasma membrane, indicating the possible site of its action. Altogether, this study highlights that XopL is an important TTSS-effector of Xap that suppresses plant immune responses, including PCD, presumably to support the multiplication of Xap for a sufficient time-period during blight disease development.
基金supported by the National Natural Science Foundation of China(31830072)the National Transgenic Major Program(2016ZX08001–002).
文摘Plant pathogenic bacteria engage in an ongoing struggle for survival.Gram negative phytopathogenic prokaryotes deploy typeⅢsecretion system to deliver effector proteins into plant cells to manipulate the host cellular environment.In many cases,the targets of these effector proteins are unknown.The bacterial blight pathogen,Xanthomonas oryzae pv.oryzae(Xoo),causes a devastating disease in rice and the Xoo-rice interaction is an example of the ongoing evolutionary battle between plants and pathogens.In this study,we show that an effector XopL from Xoo exhibits E3 ubiquitin ligase activity and induces cell death in the nonhost Nicotiana benthamiana(Nb).Through yeast two-hybrid,co-immunoprecipitation,and biomolecular fluorescence complementation assays,it was shown that XopL interacts with ferredoxin(NbFd),an electron transport molecule in plant chloroplasts.XopL induced defense-related response in Nb and specifically targeted NbFd for ubiquitination and ubiquitin-mediated degradation,a process that increased the production of reactive oxygen species(ROS).This study demonstrates the ubiquitination and degradation of NbFd as a result of XopL activity,which further illustrates the tremendous functional diversity in Xanthomonas effector proteins.
