Three New Pierce's Disease Pathogenicity Effectors Identified Using Xylella fastidiosa Biocontrol Strain EB92-1

Shujian Zhang; Pranjib K Chakrabarty; Laura A Fleites; Patricia A Rayside; Donald L Hopkins; Dean W Gabriel

doi:10.1371/journal.pone.0133796

Three New Pierce's Disease Pathogenicity Effectors Identified Using Xylella fastidiosa Biocontrol Strain EB92-1

PLoS One. 2015 Jul 28;10(7):e0133796. doi: 10.1371/journal.pone.0133796. eCollection 2015.

Authors

Shujian Zhang¹, Pranjib K Chakrabarty¹, Laura A Fleites¹, Patricia A Rayside¹, Donald L Hopkins², Dean W Gabriel¹

Affiliations

¹ Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America.
² Mid-Florida Research and Education Center, University of Florida, Apopka, Florida, United States of America.

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.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Bacterial Proteins* / genetics
Bacterial Proteins* / metabolism
Genome, Bacterial*
Plant Diseases / microbiology*
Sambucus / microbiology*
Virulence Factors* / genetics
Virulence Factors* / metabolism
Vitis / microbiology*
Xylella* / genetics
Xylella* / metabolism
Xylella* / pathogenicity

Substances

Bacterial Proteins
Virulence Factors

Grants and funding

University of California Pierce’s Disease Research Grants Program, project 2009-244. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.