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T. Page Owen

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Protein phosphorylation mediated by protein kinases is important in plant immune signaling transduction and has been extensively investigated. The reverse action of protein dephosphorylation via protein phosphatases, however, is less understood. Based on transcriptome data, 14 tomato PP2C phosphatases were identified which may be involved in pattern triggered immunity (PTI). These PP2C phosphatases were named as PP2C immunity-associated candidates (Pic). In the context of this current project, four Pic proteins were screened for their impact on resistance to the bacterial pathogen, Pseudomonas syringae pv. tomato (Pst). Using loss-of-function mutants, the roles of four Pic proteins were characterized for overall impact on growth of Pst, and their possible effect on Reactive Oxygen Species (ROS) production or the mitogen-activated protein kinase (MAPK) pathways. Additionally, we used an agrobacterium-mediated transient overexpression approach to further examine the function of Pic5, Pic10 and Pic12 in the regulation of immune pathways. Our results showed that a loss-of-function mutation in Pic2, Pic5 or Pic10 did not significantly alter disease resistance to Pst. Also, ROS production and MAPK activation in these mutants were not affected. Interestingly, we found loss-of-function pic12 mutant had enhanced disease resistance to Pst and likely is involved with the MAPK cascade. This research can provide insight into the molecular mechanisms of the plant immune response and further inform plant breeders on ways to develop more disease resistant crops.



The views expressed in this paper are solely those of the author.