Horticulture and Crop Science PhD student, Lin Jin was awarded the William E. Krauss Director's Award for Excellence in Graduate Research for her publication, "Direct and Indirect Targeting of PP2A by Conserved Bacterial Type-III Effector Proteins" (Lin et al., 2016; PLOS Pathogens; DOI:10.1371/jouranl.ppat.1005609, published May 2016.) The Kruass Director's Award is a $1,000 award and recipients will receive a framed copy of their reprint paper which will be presented at the annual OARDC Research Conference on April 20, 2017. This award serves to emphasize the importance to doctoral students of publishing their data in a refereed journal and rewards the student for producing the highest quality peer-reviewed research.
"Lin’s paper is significant to both basic and applied research. Identification of the direct target of AvrE-family effectors opens new avenues for basic research to understand how the mechanistic connection to PP2A underlies AvrE-family effector virulence function in planta. Similarly, this knowledge paves the way for rational breeding and biotechnological approaches to produce plants unaffected by the action of AvrE-family effectors." - Dr. Dave Mackey, Lin Jin's advisor
Direct and Indirect Targeting of PP2A by Conserved Bacterial Type-III Effector Proteins
Bacterial AvrE-family Type-III effector proteins (T3Es) contribute significantly to the virulence of plant-pathogenic species of Pseudomonas, Pantoea, Ralstonia, Erwinia, Dickeya and Pectobacterium, with hosts ranging from monocots to dicots. However, the mode of action of AvrE-family T3Es remains enigmatic, due in large part to their toxicity when expressed in plant or yeast cells. To search for targets of WtsE, an AvrE-family T3E from the maize pathogen Pantoea stewartii subsp. stewartii, we employed a yeast-two-hybrid screen with non-lethal fragments of WtsE and a synthetic genetic array with full-length WtsE. Together these screens indicate that WtsE targets maize protein phosphatase 2A (PP2A) heterotrimeric enzyme complexes via direct interaction with B’ regulatory subunits. AvrE1, another AvrE-family T3E from Pseudomonas syringae pv. tomato strain DC3000 (Pto DC3000), associates with specific PP2A B’ subunit proteins from its susceptible host Arabidopsis that are homologous to the maize B’ subunits shown to interact with WtsE. Additionally, AvrE1 was observed to associate with the WtsE-interacting maize proteins, indicating that PP2A B’ subunits are likely conserved targets of AvrE-family T3Es. Notably, the ability of AvrE1 to promote bacterial growth and/or suppress callose deposition was compromised in Arabidopsis plants with mutations of PP2A genes. Also, chemical inhibition of PP2A activity blocked the virulence activity of both WtsE and AvrE1 in planta. The function of HopM1, a Pto DC3000 T3E that is functionally redundant to AvrE1, was also impaired in specific PP2A mutant lines, although no direct interaction with B’ subunits was observed. These results indicate that sub-component specific PP2A complexes are targeted by bacterial T3Es, including direct targeting by members of the widely conserved AvrE-family.
Read Lin Jin's paper here.