The Pseudomonas syringae effector protein HopZ1a suppresses effector-triggered immunity.
*The Pseudomonas syringae pv syringae type III effector HopZ1a is a member of the HopZ effector family of cysteine-proteases that triggers immunity in Arabidopsis. This immunity is dependent on HopZ1a cysteine-protease activity, and independent of known resistance genes. We have previously shown that HopZ1a-triggered immunity is partially additive to that triggered by AvrRpt2. These partially additive effects could be caused by at least two mechanisms: their signalling pathways share a common element(s), or one effector interferes with the response triggered by the other. *Here, we investigate the molecular basis for the partially additive effect displayed by AvrRpt2- and HopZ1a-triggered immunities, by analysing competitive indices, hypersensitive response and symptom induction, PR-1 accumulation, expression of PR genes, and systemic acquired resistance (SAR) induction. *Partially additive effects between these defence responses require HopZ1a cysteine-protease activity, and also take place between HopZ1a and AvrRps4 or AvrRpm1-triggered responses. We establish that HopZ1a-triggered immunity is independent of salicylic acid (SA), EDS1, jasmonic acid (JA) and ethylene (ET)-dependent pathways, and show that HopZ1a suppresses the induction of PR-1 and PR-5 associated with P. syringae pv tomato (Pto)-triggered effector-triggered immunity (ETI)-like defences, AvrRpt2-triggered immunity, and Pto or Pto (avrRpt2) activation of SAR, and that suppression requires HopZ1a cysteine-protease activity. *Our results indicate that HopZ1a triggers an unusual resistance independent of known pathways and suppresses SA and EDS1-dependent resistance.
Macho
Alberto P
AP
Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain.
Guevara
Carlos M
CM
Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain.
Tornero
Pablo
P
Instituto de Biología Molecular y Celular de Plantas (Universidad Politécnica de Valencia - CSIC) Avda de los Naranjos s/n. Valencia E-46022, Spain.
Ruiz-Albert
Javier
J
Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain.
Beuzón
Carmen R
CR
Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain.
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D057056:Cysteine Proteases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D054884:Host-Pathogen Interactions; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D057865:Plant Immunity / Q000235:genetics; D044224:Pseudomonas syringae / Q000378:metabolism / Q000472:pathogenicity*; D020156:Salicylic Acid / Q000378:metabolism
D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C118837:EDS1 protein, Arabidopsis; D057056:Cysteine Proteases; D020156:Salicylic Acid