Experience of transient environmental stress can prepare (“prime”) the phenotype of an organism for improved responses to impending stress. Successful priming of a stress response by a past environmental cue requires memory of the past experience. While ample knowledge is available on memory processes in animals, we need a deeper understanding of how organisms lacking a nervous system store an environmental experience, how they retrieve the memory and how it affects the response to impending stress. In addition to these mechanistic “how”-questions, scarce knowledge is available on the ecological traits that determine the benefit of remembering a past stress. The Collaborative Research Centre (CRC) 973 focuses on studies of (1) the mechanisms of priming and memory of stress responses in organisms without nervous systems and (2) the ecological conditions favouring priming and memory. The CRC 973 projects investigate priming and memory of stress responses especially in plants, but also in bacteria and fungi. Hence, organisms with different life strategies are studied, i.e. r-selected species with a high reproduction rate and short life time, and K-selected ones with a lower reproduction rate and longer life time. The stressors applied include abiotic (cold, heat, light) and biotic (antimicrobial peptides, phytopathogens, herbivorous insects) stimuli, thus allowing for comparative analysis of priming processes with regard to the type of stressor.

In phase II, CRC 973 intends to further pursue its strategic aim, namely to more tightly link research in molecular biology and biochemistry with ecology. Reaching this aim will be supported by a CRC-implemented programme for PhD students; this Integrated Research Training Group (IRTG) programme offers teaching in the various biological disciplines covered by CRC 973, ranging from molecular biology and biochemistry to ecology.

CRC 973 will place special research emphasis on the temporal and spatial aspects of the priming process. We intend to investigate (i) which factors determine the temporal course of priming and the persistence of memory and which ones regulate “forgetting” of information, i.e. resetting the primed state to the non-primed one, and (ii) how priming information is spatially transmitted within a plant from seeds, meristems or fully developed tissue to later developing tissue. The latter question will be addressed by analysing epigenetic information transfer via mitosis and the functional relevance of transcription factors and phytohormones. Furthermore, we will study – in addition to the role of the organism´s life strategy – some further ecological factors that may shape priming and memory processes, i.e. the impact of the age of the primed target organism and the role of the presence of competitors and predatory species. Field studies will investigate the ecological relevance of priming under natural conditions. In addition, a project working with bacteria will investigate the evolution of phenotypic primability for improved stress resistance.

Project area A: Priming and Memory: Temperature Stress

A1	Priming in fungi – towards understanding priming at the level of the community	Prof. Dr. Matthias C. Rillig &  Prof. Dr. Britta Tietjen
A2	Priming the chromatin in response to heat stress in Arabidopsis thaliana	Prof. Dr. Isabel Bäurle
A3	Low temperature priming and memory in Arabidopsis thaliana	Prof. Dr. Bernd Müller-Röber
A4*	CDPKs in priming in response to low temperature in Arabidopsis thaliana	Prof. Dr. Tina Romeis
A5	The control of plant growth by thermopriming	Prof. Dr. Bernd Müller-Röber
A6*	The role of heat shock proteins and autophagy for thermomemory	Dr. Salma Balazadeh

Project area B: Priming and Memory: Stress by Herbivory

B1	Priming of elm defence against herbivores	Prof. Dr. Monika Hilker
B2*	Plant priming of anti-herbivore defences by insect oviposition	Prof. Dr. Anke Steppuhn
B3*	Priming of plant defence by below- and aboveground herbivores	Jun. Prof. Dr. Susanne Wurst
B4	Priming of defence against herbivores feeding upon Arabidopsis thaliana	Dr. Vivien Lortzing
B5*	Priming of plant defence against pathogens and herbivores by DNA damage signalling	Dr. Lennart Wirthmüller

Project area C: Priming and Memory: Various Stressors

C1	Priming of environmental responses in Arabidopsis thaliana by cytokinin	Prof. Dr. Thomas Schmülling
C2	Priming in biotic stress responses mediated by CDPK signalling	Prof. Dr. Tina Romeis
C3*	Impact of root- and leaf-associated bacteria on metabolic priming of Arabidopsis for subsequent bacteria colonisation	Dr. habil. Joachim Kopka
C4	The chloroplast antioxidant system as a priming hub in plant stress management	Prof. Dr. Margarete Baier & Dr. Thomas Griebel
C5	Bacterial priming against antimicrobials and the evolution of ‘primability’	Prof. Dr. Jens Rolff
C6*	Proteasomal protein turnover during immune priming in Arabidopsis	Prof. Dr. Frederik Börnke
C7	Mechanisms of long-term, epigenetic stress memory in annual and perennial Brassicaceae species	Prof. Dr. Daniel Schubert
C8	Priming and memory of Staphylococcus aureus in response to oxidative and electrophile stress	Prof. Dr. Haike Antelmann

Project Z:

INF	The database ‘PrimeDB’: A storage, search and analysis platform for experimental data on priming and memory of organismic responses to stress	PD Dr. habil. Dirk Walther
IRTG	Biocommunication: Mechanisms and consequences of information storage and retrieval in plants and microbes	Prof. Dr. Britta Tietjen & Prof. Dr. Daniel Schubert
Z	Central management tasks and administration	Prof. Dr. Monika Hilker

* projects are completed within phase I