Dear EMBRIO Members, A reminder that we won't meet today. For Thrusts that don't already have a standing meeting, please consider using this bi-weekly blocked time of Monday 3-4pm ET. Biweekly dates remaining this semester that we won't hold the all-hands Weekly Nov. 27 Dec. 11 Mark your calendars for our EMBRIO session next Monday, November 20th, Dr. Weiwei Zhang in the Staiger Lab will present a research seminar titled Decoding Ca2+ signatures and signaling to the actin cytoskeleton during the plant innate immune response. This work in Thrust 2 that Dr. Zhang is presenting includes collaborations with multiple EMBRIO labs that are working with the Staiger lab to develop data analysis tools and mathematical models. Decoding Ca2+ signatures and signaling to the actin cytoskeleton during the plant innate immune response Abstract Plants have evolved conserved molecular mechanisms to recognize microbe-associated or damage-associated molecular patterns (MAMPs or DAMPS), mechanical perturbation, and/or cell wall integrity changes to initiate the first layer of defense response known as pattern-triggered immunity or PTI. During the first few minutes of PTI, several hallmark cellular responses occur including influxes of Ca2+ into the cytosol, accumulation of the signaling lipid phosphatidic acid, a transient reactive oxygen species (ROS) burst, and remodeling of the actin cytoskeleton. Among these hallmark events, cytosolic Ca2+ signals are recognized as a key early signaling element as they are highly specific in duration, amplitude, and frequency, and therefore encode specific information and trigger distinct downstream signaling pathways in response to different stimuli. Despite their obvious importance, Ca2+ signatures and how they spread in space and time in response to different stimuli during PTI have not been carefully characterized nor are the molecular mechanisms encoding these spatiotemporal Ca2+ signatures well understood. In this work, we developed an image acquisition and analysis pipeline to study plant defense related Ca2+ dynamics in Arabidopsis cotyledon epidermal cells using the live cell calcium biosensor R-GECO1. We characterized both single-cell Ca2+ signatures as well as intercellular Ca2+ wave patterns in response to two types of stimuli that mimic pathogen attack: global chemical stimulation with MAMPs and local mechanical stimulation by single-cell laser ablation. In addition, we show that pre-disruption of the cortical actin cytoskeleton resulted in altered single-cell Ca2+ signatures and increased calcium signaling durations, suggesting a negative feedback mechanism between the actin cytoskeleton and calcium signaling during PTI. Our work will help understand the calcium signaling mechanisms as well as the spatial spread of immune signals across a tissue during plant defense against pathogens. Brent T. Ladd, Senior Research Program Manager, EMBRIO Institute<https://www.purdue.edu/research/embrio/> Weldon School of Biomedical Engineering, Purdue University Office: Hall for Discovery Learning and Research, Ste. 203 207 S. Martin Jischke Drive West Lafayette, IN 47907 laddb@purdue.edu <https://www.purdue.edu/research/embrio/>