title: Quantitative, Image-Based Phenotyping Methods Provide Insight into Spatial and Temporal Dimensions of Plant Disease.
abstract: Plant disease symptoms exhibit complex spatial and temporal patterns that are challenging to quantify. Image-based phenotyping approaches enable multidimensional characterization of host-microbe interactions and are well suited to capture spatial and temporal data that are key to understanding disease progression. We applied image-based methods to investigate cassava bacterial blight, which is caused by the pathogen Xanthomonas axonopodis pv. manihotis (Xam). We generated Xam strains in which individual predicted type III effector (T3E) genes were mutated and applied multiple imaging approaches to investigate the role of these proteins in bacterial virulence. Specifically, we quantified bacterial populations, water-soaking disease symptoms, and pathogen spread from the site of inoculation over time for strains with mutations in avrBs2, xopX, and xopK as compared to wild-type Xam ∆avrBs2 and ∆xopX both showed reduced growth in planta and delayed spread through the vasculature system of cassava. ∆avrBs2 exhibited reduced water-soaking symptoms at the site of inoculation. In contrast, ∆xopK exhibited enhanced induction of disease symptoms at the site of inoculation but reduced spread through the vasculature. Our results highlight the importance of adopting a multipronged approach to plant disease phenotyping to more fully understand the roles of T3Es in virulence. Finally, we demonstrate that the approaches used in this study can be extended to many host-microbe systems and increase the dimensions of phenotype that can be explored.
authors.affiliation: Donald Danforth Plant Science Center, Saint Louis, MO 63132.
authors.forename: Andrew M
authors.identifier: 0000-0002-6711-821X
authors.initials: AM
authors.lastname: Mutka
authors.affiliation: Donald Danforth Plant Science Center, Saint Louis, MO 63132.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Fentress
authors.affiliation: Donald Danforth Plant Science Center, Saint Louis, MO 63132.
authors.forename: Joel W
authors.initials: JW
authors.lastname: Sher
authors.affiliation: Donald Danforth Plant Science Center, Saint Louis, MO 63132.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Berry
authors.affiliation: Donald Danforth Plant Science Center, Saint Louis, MO 63132.
authors.forename: Chelsea
authors.initials: C
authors.lastname: Pretz
authors.affiliation: Donald Danforth Plant Science Center, Saint Louis, MO 63132.
authors.forename: Dmitri A
authors.identifier: 0000-0002-0497-1723
authors.initials: DA
authors.lastname: Nusinow
authors.affiliation: Donald Danforth Plant Science Center, Saint Louis, MO 63132 rbart@danforthcenter.org.
authors.forename: Rebecca
authors.identifier: 0000-0003-1378-3481
authors.initials: R
authors.lastname: Bart
mesh_terms: D001937:Brassica / Q000382:microbiology; D002212:Capsicum / Q000382:microbiology; D054884:Host-Pathogen Interactions; D008163:Luminescent Measurements / Q000379:methods*; D018551:Solanum lycopersicum / Q000382:microbiology; D002365:Manihot / Q000382:microbiology; D009154:Mutation; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D058526:Plant Vascular Bundle / Q000382:microbiology*; D010944:Plants / Q000145:classification / Q000382:microbiology*; D015203:Reproducibility of Results; D062206:Spatial Analysis; D014764:Viral Proteins / Q000235:genetics; D014774:Virulence / Q000235:genetics; D014974:Xanthomonas / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*
chemical_list: D014764:Viral Proteins