Temperature-dependent control of flowering by the gibberellin pathway and interactions between DELLA proteins and APETALA1/VRN1 MADS-box factors.

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Temperature is an important environmental cue controlling flowering time. In Arabidopsis, the experience of cold temperatures delays growth and flowering and, at the molecular level, cold results in the accumulation of DELLA proteins, major plant growth and flowering time repressors of the gibberellin (GA) signalling pathway. DELLA abundance responds rather instantly to changes in the temperature and the effects of DELLA accumulation can be suppressed by GA (treatments). We have previously shown that the Arabidopsis MADS-box transcription factor APETALA1 (AP1) is repressed by direct interactions with DELLAs. Furthermore, we have evidence that increased AP1 expression may be causative for the early flowering of two Arabidopsis accessions in cold temperature. Here, we would like to test the hypothesis that increased AP1 levels in these accessions outcompete the growth repressive effects of DELLAs in the cold. Second, we would like to test whether this AP1-DELLA regulatory module is conserved in cereal species. In barley and wheat, VERNALIZATION1 (VRN1) proteins, the closest homologues to Arabidopsis AP1, are major flowering time regulators. We therefore would like to examine whether barley and wheat VRN1 can also interact with the respective DELLAs and whether flowering time control in response to temperature and GA is dependent on this interaction.