Novel insights into strigolactone distribution and signalling

• SL bioactivity studies suggest modulations of perception among different organisms.
• SL enzymatic hydrolysis is essential to the signalling pathway.
• SL perception/signalling may highlight a novel mechanism among plant hormones.
• SLs were present before land colonization and their first function could likely be hormonal.

Strigolactones (SLs), a group of small carotenoid-derived molecules, were first known for their function in the rhizosphere in both symbiotic and parasitic interactions. Most of the progress for deciphering SL biosynthesis and signalling pathways comes from the use of high branching mutants identified in several species demonstrating that SLs also play a hormonal role in plant development. How SLs are perceived by the different organisms on which they show bioactivity is a current major challenge for the growing SL research community. These molecules very likely predate the colonization of land by plants and represent a fascinating example of signalling molecules involved in key innovations during plant evolution.