Delay in Flowering Time in Col-0 Under Water Deficit and in the Triple Methylation Knockout Mutant Is Correlated with Shared Overexpression of and .

This study addresses the role of cytosine methylation in the fine-tuning of flowering time under water deficit in A triple methylation mutant was used together with the Col-0 wild type. The plants were grown under long-day conditions with water deficit induced by cessation of watering starting 12 days after seeding. Col-0 showed a 1-day delay in flowering as a result of the treatment. In contrast, showed a 2-day delay regardless of the experimental conditions. We found that the two b-box domain proteins, BBX16/COL7 and BBX17/COL8, became overexpressed in the background and in Col-0 under water deficit 24 days after seeding. Additionally, the NF-YA2 transcription factor became correspondingly down-regulated. Our results support a model where BBX16/COL7 and BBX17/COL8 interact with CONSTANS to delay the induction of under long-day conditions. , which is also recognized as a promoter of expression, with its down-regulation causes additional delay of -induced flowering. The plants overcome the BBX/NF-YA inhibition easily, resulting in a relatively small delay in flowering. The expression patterns of the three genes suggest the involvement of cytosine methylation in their regulation; however, no differential methylation could be found in that can explain these effects. The results therefore suggest a acting mechanism. Considering that the activities of and in different physiological conditions are not elucidated, this paper provides a background for future experiments targeting the role of these genes in the fine-tuning of flowering time in .