DSSS - Making a flat leaf: Pre-patterning, morphogenic small RNAs, and Turing dynamics

  • Datum: 14.02.2025
  • Uhrzeit: 15:00 - 16:00
  • Vortragende: Prof. Marja Timmermans
  • Center for Plant Molecular Biology, University of Tübingen
  • Ort: NO.002, MPI für Intelligente Systeme
 DSSS - Making a flat leaf: Pre-patterning, morphogenic small RNAs, and Turing dynamics

As the principal photosynthetic organ, a leaf commonly develops as a thin, flat lamina optimized for light capture and gas exchange. The flat geometry appears deceptively simple. In reality, its production poses an unusual and mechanistically challenging problem; namely, how to create a stable dorsoventral (top-bottom) boundary within the plane of a long and wide, but shallow, structure that grows orders of magnitude in size. We have shown that the spatial information needed to specify dorsal (top) versus ventral (bottom) fate is provided by a pre-pattern at the shoot stem cell niche responsible for all post-embryonic shoot growth. This pre-pattern converts a uniform signaling input from the organogenic hormone auxin into a ARF-dependent binary response output to distinguish dorsal from ventral identity. As the leaf primordium emerges from the pre-patterned niche environment, the initial polarity resolves into an intricate system of transcription factor interactions that reinforce either dorsal or ventral cell fate. Their spatial arrangement at the organ level is further governed by mobile small RNAs that act as morphogens and generate sharply defined domains of target gene expression through an intrinsic threshold-based readout of their accumulation gradients. Our most recent findings show that this gene regulatory network follows the organizing principles of a Turing system. Dorsoventral polarity is thus propagated by a self-organizing system of small RNA - transcription factor interactions. This system dynamically adapts to internal and external perturbations to sustain the robust polarity boundary in planar leaves, but at the same time provides flexibility to support morphological diversity.

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