title: The AvrB_AvrC domain of AvrXccC of Xanthomonas campestris pv. campestris is required to elicit plant defense responses and manipulate ABA homeostasis.
abstract: Plant disease induced by Xanthomonas campestris pv. campestris depends on type III effectors but the molecular basis is poorly understood. Here, AvrXccC8004 was characterized, and it was found that the AvrB_AvrC domain was essential and sufficient to elicit defense responses in an Arabidopsis-resistant ecotype (Col-0). An upregulation of genes in responding to the AvrB_AvrC domain of AvrXccC8004 was shown in a profile of host gene expression. The molecular changes were correlated with morphological changes observed in phenotypic and ultrastructural characterizations. Interestingly, the abscisic acid (ABA)-signaling pathway was also a prominent target for the AvrB_AvrC domain of AvrXccC8004. The highly elicited NCED5, encoding a key enzyme of ABA biosynthesis, was increased in parallel with ABA levels in AvrXccC8004 transgenic plants. Consistently, the X. campestris pv. campestris 8004 ΔavrXccC mutant was severely impaired in the ability to manipulate the accumulation of ABA and induction of ABA-related genes in challenged leaves. Moreover, exogenous application of ABA also enhanced the susceptibility of Arabidopsis to the X. campestris pv. campestris strains. These results indicate that the AvrB_AvrC domain of AvrXccC8004 alone has the activity to manipulate ABA homeostasis, which plays an important role in regulating the interactions of X. campestris pv. campestris and Arabidopsis.
authors.affiliation: Institute of Biochemistry, National ChungHsing University, Taichung, Taiwan.
authors.forename: Yi-Ping
authors.initials: YP
authors.lastname: Ho
authors.forename: Choon Meng
authors.initials: CM
authors.lastname: Tan
authors.forename: Meng-Ying
authors.initials: MY
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Lin
authors.forename: Wen-Ling
authors.initials: WL
authors.lastname: Deng
authors.forename: Jun-Yi
authors.initials: JY
authors.lastname: Yang
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D010935:Plant Diseases / Q000382:microbiology; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D014774:Virulence / Q000235:genetics / Q000502:physiology; D016959:Xanthomonas campestris / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; D000040:Abscisic Acid