P-436 - Identification of Pseudomonas effector-delivered plant cells in the native spatial context of ETI by leveraging TALE

Recent studies suggest that effector-triggered immunity (ETI) is spatially coordinated across neighboring cells, including non-cell-autonomous responses. However, it remains a challenge to distinguish effector-delivered cells at the microscopic level during early stages of bacterial pathogen infection. To address this challenge, we utilized transcription activator-like effectors (TALEs) as a tool to rapidly amplify the expression of effector-induced reporter and exclusively label effector-delivered plant cells. In this study, we equipped the model bacterial pathogen, Pseudomonas syringae pv. tomato DC000 (Pst) with a synthetic TALE that specifically drives the expression of nuclear-localized fluorophores in Nicotiana benthamiana and Arabidopsis reporter lines. Upon infection with Pst carrying TALE, we detected nuclear-localized fluorescence from TALE-delivered plant cells as early as 7 hours post-infection, even at extremely low bacterial densities (OD₆₀₀ of 0.0001), a concentration comparable to early-stage Pst infections. To our knowledge, this is the first report of incorporating functional TALE into model Pst pathosystem. We believe that our novel Pst-TALE system will serve as a powerful tool for advancing our understanding of spatially coordinated ETI responses, especially when integrated with cutting-edge spatial transcriptomics technologies.