title: Three New Pierce's Disease Pathogenicity Effectors Identified Using Xylella fastidiosa Biocontrol Strain EB92-1.
abstract: Xylella fastidiosa (X. fastidiosa) infects a wide range of plant hosts and causes economically serious diseases, including Pierce's Disease (PD) of grapevines. X. fastidiosa biocontrol strain EB92-1 was isolated from elderberry and is infectious and persistent in grapevines but causes only very slight symptoms under ideal conditions. The draft genome of EB92-1 revealed that it appeared to be missing genes encoding 10 potential PD pathogenicity effectors found in Temecula1. Subsequent PCR and sequencing analyses confirmed that EB92-1 was missing the following predicted effectors found in Temecula1: two type II secreted enzymes, including a lipase (LipA; PD1703) and a serine protease (PD0956); two identical genes encoding proteins similar to Zonula occludens toxins (Zot; PD0915 and PD0928), and at least one relatively short, hemagglutinin-like protein (PD0986). Leaves of tobacco and citrus inoculated with cell-free, crude protein extracts of E. coli BL21(DE3) overexpressing PD1703 exhibited a hypersensitive response (HR) in less than 24 hours. When cloned into shuttle vector pBBR1MCS-5, PD1703 conferred strong secreted lipase activity to Xanthomonas citri, E. coli and X. fastidiosa EB92-1 in plate assays. EB92-1/PD1703 transformants also showed significantly increased disease symptoms on grapevines, characteristic of PD. Genes predicted to encode PD0928 (Zot) and a PD0986 (hemagglutinin) were also cloned into pBBR1MCS-5 and moved into EB92-1; both transformants also showed significantly increased symptoms on V. vinifera vines, characteristic of PD. Together, these results reveal that PD effectors include at least a lipase, two Zot-like toxins and a possibly redundant hemagglutinin, none of which are necessary for parasitic survival of X. fastidiosa populations in grapevines or elderberry.
authors.affiliation: Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Shujian
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Pranjib K
authors.initials: PK
authors.lastname: Chakrabarty
authors.affiliation: Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Fleites
authors.affiliation: Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Rayside
authors.affiliation: Mid-Florida Research and Education Center, University of Florida, Apopka, Florida, United States of America.
authors.forename: Donald L
authors.initials: DL
authors.lastname: Hopkins
authors.affiliation: Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Dean W
authors.initials: DW
authors.lastname: Gabriel
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D016680:Genome, Bacterial; D010935:Plant Diseases / Q000382:microbiology*; D027923:Sambucus / Q000382:microbiology*; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D027843:Vitis / Q000382:microbiology*; D044167:Xylella / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors