Dear Editor,Strigolactones (SLs) are a class of carotenoid-derived plant hormones that regulate shoot branching among other developmental processes (Gomez-Roldan et al.,2008;Umehara et al.,2008;Al-Babili and Bouwmeester,2015).In addition,SLs are released by roots as a chemical signal attracting symbiotic arbuscular mycorrhizal fungi.However,this signal is also perceived by seeds of root parasitic weeds,announcing the presence of a host and triggering germination (Al-Babili and Bouwmeester,2015).Natural SLs consist of a butenolide ring (D ring) connected by an enol ether bridge to a tricyclic lactone (ABC rings) in canonical SLs,such as strigol,and to a variable,second moiety in non-canonical SLs,such as methyl carlactonoate.There are around 25 known natural SLS (Xie,2016) that differ in the stereochemistry of the B/C junction and in modifications of the ABC-ring of canonical SLS,and in the structure of the second moiety of the non-canonical ones (Al-Babili and Bouwmeester,2015).Carlactone (CL),the central intermediate in SL biosynthesis,is a C19 molecule derived from all-trans-β-carotene by the sequential action of three enzymes through a stereospecific pathway.