Poster abstracts
Poster number 56 submitted by Reid Gohmann
Investigating virulence of AvrE1 in isolation of other type III effectors
Reid Gohmann (Molecular, Cellular, Developmental Biology), David Mackey (Horticulture and Crop Science)
Abstract:
During infection, many phytopathogenic bacteria translocate type III effector proteins (T3Es) directly into the cytoplasm of host cells where they carry out diverse functions to promote virulence. T3Es often disrupt host immunity, but effectors of the widely-conserved AvrE-family are thought to promote virulence by establishing a niche that supports rapid and robust growth of the bacteria. For example, both AvrE1 from Pseudomonas syringae pathovar tomato (Pto) and WtsE from Pantoea stewartii subsp. stewartii are required for growth and induce a “water-soaking” symptom in leaves1,2. WtsE was also shown to induce host metabolism genes and cause accumulation of metabolites in the extracellular space colonized by the pathogen2. Recently, DspE from Erwinia amylovora was shown to fold into a β-barrel pore-like structure that conferred water and solute permeability to Xenopus oocytes3, highlighting its function as a channel that can allow cytoplasmic contents to flow outside the cell.
Phytopathogenic bacteria typically employ a large arsenal of T3Es, with Pto having 36 known effectors4. In planta research typically relies on strains lacking AvrE1, but these strains still deliver the remaining effectors. To study the in planta effects of AvrE1 separate from the other effectors, we used the Pto strain D36E, in which all 36 effectors have been deleted. By adding AvrE1 back to D36E, we found that it is sufficient to support a moderate degree of growth without causing significant cell death in infected leaves. Furthermore, the growth conferred by AvrE1 is further increased by mutations in host immune system genes, indicating that immune suppression can work together with AvrE1-induced niche establishment to confer robust pathogen growth.
Future studies will examine the composition of extracellular fluid to determine the impact of AvrE1 on niche establishment. Additionally, effects of AvrE1 on reprogramming host defense and metabolism will be investigated by RNA sequencing.
References:
1Ekanayake, G., et al. A method for quantitation of apoplast hydration in Arabidopsis leaves reveals water-soaking activity of effectors of Pseudomonas syringae during biotrophy. Sci Rep 12, 18363 (2022)
2Gentzel I. et al. Dynamic nutrient acquisition from a hydrated apoplast supports biotrophic proliferation of a bacterial pathogen of maize. Cell Host Microbe 30(4):502-517.e4. (2022)
3Nomura, K., et al. Bacterial pathogens deliver water- and solute-permeable channels to plant cells. Nature 621, 586–591 (2023)
4Wei, H.L., et al. Pseudomonas syringae pv. tomato DC3000 Type III Secretion Effector Polymutants Reveal an Interplay between HopAD1 and AvrPtoB. Cell Host Microbe. 10;17(6):752-62. (2015)
Keywords: Plant pathology, Niche establishment, Type III effectors