Several studies described in last decades, how plants can cope with different single stress events. But in nature, plants are rather exposed to different stress combinations and series of stress events. Under such fluctuating conditions, it is beneficial for the plant fitness to maintain information from a past transient stress, called priming stimulus, over a stress-free period to be prepared for a subsequent second stress event. One example is the process of cold priming where plants adjust their plastid antioxidant system after a first cold exposure and thereby adjust their response to a second cold stress, also both treatments are separated by stress free period. In my thesis, I investigated the impact of cold priming on the cold and high light response of Arabidopsis thaliana. Comparative transcriptome analyses revealed that most of the cold priming imprints in the high light and cold response are stress type specific. Some genes showed even an inverse priming-regulation upon cold and high light, which indicates an active reprograming of the plant memory in response to both triggering stimuli. One of the few triggering type independent effects of cold priming was the downregulation of genes of the jasmonic acid (JA) metabolism upon the first hour of high light and cold application. The impact of cold priming on stress responsive JA metabolism was further investigated upon cold triggering and showed that priming impacts on the cold inducible lipid oxidation. Genetic analysis dissected the role of JA metabolism and indicates that cold priming responsive genes are regulated by the JA precursor cis-(+)-12-oxo-phytodienoic acid (OPDA). A casual connection between the known cold priming effects and the cold response of OPDA metabolic genes could be shown by transient expression of the thylakoid located ascorbate peroxidase (tAPX). In summary, my thesis showed a strong impact of OPDA in the cold priming regulated cold response. The comparative transcriptome analyses indicate that cold priming effects also the high light response of OPDA metabolic genes. However, OPDA responsive genes showed triggering type specific priming regulation, which points to a cold and a high light specific impact of the cold priming reduced OPDA metabolism.
