Capsella rubella: My Fruity Valentine

Most shapes in plant organs are pre-determined at the primordial stage and from this point, growth will establish and maintain this shape. Rarely will re-shaping of an organ occur post-organogenesis. However, Hu et al. describe a notable exception in Capsella rubella, a close relative of Arabidopsis thaliana. Capsella’s female reproductive organ, the gynoecium, undergoes a geometric rearrangement where its initially flat, spheroidal structure is re-shaped into a heart-shape upon fertilization. Hu et al. used a complex of technologies from single cell RNA sequencing to whole-organ live cell imaging to piece together the mechanisms underlying re-shaping. At the cellular level, this paper provides evidence that a gradient of differentiation, as well as regional anisotropic growth (different growth in different directions), support the re-shaping of the gynoecium. Molecularly, they identified an important gene supporting this process: SHOOTMERISTEMLESS (CrSTM). CrSTM expression is induced by local auxin signaling. CrSTM then binds a specific region in its own promoter to maintain its expression through an autoregulatory positive feedback loop. Intriguingly, this STM self-binding site is conserved throughout Brassicaceae species which re-shape their gynoecia post-fertilization. Altogether these findings demonstrate the evolutionary significance of STM autoregulation, coordinated cell division, and localized growth in re-shaping. (Summary by Kes Maio @KestrelMaio @kesmaio.bsky.social) Nature Plants https://doi.org/10.1038/s41477-024-01854-1