RNA-seq Analysis of an Apical Meristem Time Series Reveals a Critical Point in Arabidopsis thaliana Flower Initiation

Floral transition is a critical event in the life cycle of a flowering plant as it determines its reproductive success. Despite extensive studies of specific genes that regulate this process, the global changes in transcript expression profiles at the point when a vegetative meristem transitions into an inflorescence have not been described. In this study we analyzed gene expression during Arabidopsis thaliana meristem development from day 7 to 16 after germination in one-day increments. The dynamics of the expression of the main flowering regulators were consistent with previous reports: notably, the expression of FLOWERING LOCUS C (FLC) decreased over the course of the time series while expression of LEAFY (LFY) increased. This analysis revealed a developmental time point between 10 and 12 days after germination where FLC expression had decreased but LFY expression had not yet increased, which was characterized by a peak in the number of differentially expressed genes. GO enrichment analysis of these genes identified an overrepresentation of genes related to the cell cycle, suggesting that during transition to the flowering stage a change in dynamics of cell division takes place. In particular, we hypothesize that a subset of the meristematic cells experiences a forced exit from G0 at day 10. Finally, we observed an acceleration of the cell cycle at day 11, which may be linked to meristem reorganization preceding activation of LFY.

30