Mechanisms of plasticity and commitment in plants

Dramatic developmental changes occur in plants also late into adulthood, one might think their epigenome is less stringent, or that they readily trigger Yamanaka-like reprogramming processes. This plasticity is largely achieved by maintenance of small clusters of multipotent cells at the plant tips, aka “meristems”. In a recent study, we developed a pipeline that allows sensitive transcriptional profiling of individual shoot apical meristems (in bulk) as they cease production of leaves and switch to a reproductive growth. Surprisingly, we found that the mild morphological changes are accompanied by rapid activation of transient gene programs. We then employed genetic tools to further examine the role of these programs during this commitment process, and found that whereas those are dispensable for timing of floral transition, they play a critical role in the way the shoot apical meristems transforms (e.g., the number of flowers in inflorescence and the release of lateral buds). However, it remains unclear what are the subpopulations within the meristem, and how those response to floral signals and others to facilitate plants ability to juggle between developmental courses. To address this fundamental aspect of plant biology at the single-cell resolution, we are currently setting up a tissue-culture callus model for epigenetic reprogramming.