The function of cytokinin in regulating flowering time
The promotive activity of cytokinin on flowering was already described soon after the discovery of this plant hormone more than fifty years ago. However, the molecular mechanisms underlying this activity remain elusive despite great progress in understanding the metabolism and signalling of the hormone. The objective of this project is to study the extent and the molecular pathways by which cytokinin regulates flowering time in Arabidopsis thaliana. In a first part, a detailed study of the consequences of loss-of-function of most of the ~60 cytokinin metabolism and signalling genes on flowering time will be performed to identify the functionally important genes. This analysis will be complemented by a study on the relevance of the cytokinin status of different tissues using transgenic plants with a tissue-specifically altered cytokinin status, focussing on the shoot apical meristem, the leaves, the phloem and the root. The investigation includes a comparison of the transcript levels of known flowering pathway genes under different day lengths and flower induction. The influence of different environmental cues on cytokinin action in regulating flowering time will be tested to understand under which circumstances its role is particularly relevant. Mining of transcriptomic data has yielded several hypotheses about a modulatory role of cytokinin in known flowering pathways which will be explored further by molecular and genetic approaches. These analyses and the identification of downstream targets type-B ARRs aim to link the action of cytokinin to known components of flowering pathways. Furthermore, a genetic approach is followed to obtain access to novel components regulating the action of cytokinin.