Plant organ shedding signal mechanism revealed

By HFSP Career Development Award holder Michael Hothorn and colleagues

Have you ever walked through a forest in the fall or through a meadow in late summer and wondered why trees and flowers shed their leaves? They are simply getting rid of organs that are no longer needed, preparing for the next step in their life cycle. But how does a leaf know when to let go? This process is regulated by the cell surface receptor HAESA, present in cells forming the tissue around the future break point. When it's time to shed an organ, a small peptide hormone called IDA instructs HAESA to initiate the shedding process.

We now demonstrate that an active, post-translationally modified IDA peptide is directly sensed by the extracellular ligand-binding domain of HAESA. IDA binding allows HAESA to recruit the co-receptor kinase SERK1 to form an active signaling complex. Interaction of the HAESA and SERK1 kinase domains in the cytoplasm triggers a signaling cascade that leads to abscission of organs.

For the full story see the press release from the University of Geneva

Figure: Molecular view of the membrane receptor signaling complex controlling plant organ shedding. The cell surface receptor HAESA is shown in blue, bound to the plant peptide hormone IDA (magenta) and the helper protein SERK1 (in orange).

Reference

Mechanistic insight into a peptide hormone signaling complex mediating floral organ abscission. Julia Santiago, Benjamin Brandt, Mari Wildhagen, Ulrich Hohmann, Ludwig A Hothorn, Melinka A Butenko, Michael Hothorn. eLife 2016;10.7554/eLife.15075 DOI: http://dx.doi.org/10.7554/eLife.15075

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Plant organ shedding signal mechanism revealed