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Printed publications

Guerra, T.; Schilling, S.; Hake, K.; Gorzolka, K.; Sylvester, F.; Conrads, B.; Westermann, B.; Romeis, T. Calcium‐dependent protein kinase 5 links calcium‐signaling with N‐Hydroxy‐L‐pipecolic acid‐ and SARD1‐dependent immune memory in systemic acquired resistance New Phytol (2019) DOI: 10.1111/nph.16147

Systemic acquired resistance (SAR) prepares infected plants for faster and stronger defense activation upon subsequent attacks. SAR requires an information relay from primary infection to distal tissue and the initiation and maintenance of a self‐maintaining phytohormone salicylic acid (SA)‐defense loop.In spatial and temporal resolution, we show that calcium‐dependent protein kinase CPK5 contributes to immunity and SAR. In local basal resistance CPK5 functions upstream of SA‐synthesis, ‐perception, and ‐signaling. In systemic tissue, CPK5 signaling leads to accumulation of SAR inducing metabolite N‐Hydroxy‐L‐pipecolic acid (NHP) and SAR marker genes including Systemic Acquired Resistance Deficient 1 (SARD1)Plants of increased CPK5‐, but not CPK6‐ signaling, display an ‘enhanced SAR' phenotype toward a secondary bacterial infection. In sard1‐1 background, CPK5‐mediated basal resistance is still mounted, but NHP level is reduced and ‘enhanced SAR' is lost.The biochemical analysis determines CPK5 half maximal kinase activity for calcium K50 [Ca2+] to ~100 nM close to the cytoplasmic resting level. This low threshold uniquely qualifies CPK5 to decode subtle changes in calcium prerequisite to signal relay and onset and maintenance of priming at later time points in distal tissue. Our data explain why CPK5 functions as a hub in basal and systemic plant immunity.
Publications

Matschi, S.; Hake, K.; Herde, M.; Hause, B.; Romeis, T. The Calcium-dependent protein kinase CPK28 regulates development by inducing growth phase-specific, spatiallyrestricted alterations in Jasmonic acid levels independent of defense responses in Arabidopsis Plant Cell 27, 591–60, (2015) DOI: 10.1105/tpc.15.00024

Phytohormones play an important role in development and stress adaptations in plants, and several interacting hormonal pathways have been suggested to accomplish fine-tuning of stress responses at the expense of growth. This work describes the role played by the CALCIUM-DEPENDENT PROTEIN KINASE CPK28 in balancing phytohormone-mediated development in Arabidopsis thaliana, specifically during generative growth. cpk28 mutants exhibit growth reduction solely as adult plants, coinciding with altered balance of the phytohormones jasmonic acid (JA) and gibberellic acid (GA). JA-dependent gene expression and the levels of several JA metabolites were elevated in a growth phase-dependent manner in cpk28, and accumulation of JA metabolites was confined locally to the central rosette tissue. No elevated resistance toward herbivores or necrotrophic pathogens was detected for cpk28 plants, either on the whole-plant level or specifically within the tissue displaying elevated JA levels. Abolishment of JA biosynthesis or JA signaling led to a full reversion of the cpk28 growth phenotype, while modification of GA signaling did not. Our data identify CPK28 as a growth phase-dependent key negative regulator of distinct processes: While in seedlings, CPK28 regulates reactive oxygen species-mediated defense signaling; in adult plants, CPK28 confers developmental processes by the tissue-specific balance of JA and GA without affecting JA-mediated defense responses. 
Publications

Seybold, H.; Trempel, F.; Ranf, S.; Scheel, D.; Romeis, T.; Lee, J. Ca2+ signalling in plant immune response: from pattern recognition receptors to Ca2+ decoding mechanisms. New Phytol 204, 782–790, (2014) DOI: 10.1111/nph.13031

Ca2+ is a ubiquitous second messenger for cellular signalling in various stresses and developmental processes. Here, we summarize current developments in the roles of Ca2+ during plant immunity responses. We discuss the early perception events preceding and necessary for triggering cellular Ca2+ fluxes, the potential Ca2+-permeable channels, the decoding of Ca2+ signals predominantly via Ca2+-dependent phosphorylation events and transcriptional reprogramming. To highlight the complexity of the cellular signal network, we briefly touch on the interplay between Ca2+-dependent signalling and selected major signalling mechanisms – with special emphasis on reactive oxygen species at local and systemic levels.
Publications

Ludwig, A.A.; Saitoh, H.; Felix, G.; Freymark, G.; Miersch, O.; Wasternack, C.; Boller, T.; Jones, J.D.G.; Romeis, T. Ethylene-mediated cross-talk between calcium-dependent protein kinase and MAPK signaling controls stress responses in plants PNAS 102, 10736-10741, (2005)

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