Review. Fellowship of the rings: a saga of strigolactones and other small signals (New Phytol)

Strigolactones are small signal molecules synthesized by plants. In the past few years, many studies highlighting the importance of this emerging phytohormone have been published. Strigolactones play important roles as a hormonal signals in plants and for mycorrhizal fungi interactions, they are present in all land plants, and the signaling pathways seem to be conserved. But what do we really know about strigolactones? Many related small molecules (like karrikins) present similar biological activity and overlapping features, showing that there is not a simple pathway but an array of related signaling pathways. Here, Machin, Hamon-Josse & Bennett, make a big effort to review the recent literature on this topic and put it into context of strigolactone complexity and evolution. Among different topics, the authors discuss chemical properties, biosynthesis, and ligand-receptor specificity of strigolactones-related compounds. Downstream proteins involved in their signaling pathway from perception to transcriptional changes are also well covered. The promiscuity of the pathway is presented as an important feature that might shape their evolution to control different developmental processes in both plant and fungi. Finally, the authors also highlight open questions that still require further research. (Summary by Facundo Romani) New Phytol.  10.1111/nph.16135)