Strigolactones: occurrence, structure, and biological activity in the rhizosphere

Strigolactones are signaling molecules that play a role in host recognition by parasitic plants of the Striga, Orobanche and Phelipanche genera which are among the most detrimental weeds in agriculture. The same class of molecules is also involved in the establishment of the symbiosis of plants with arbuscular mycorrhizal fungi. In addition, strigolactones are being shown to be involved in an increasing number of physiological processes in plants, such as the regulation of plant architecture and the response to abiotic factors such as nutrient availability and light. Important advances in knowledge about the structure determination, occurrence, biological function and physiological and biochemical regulation of the strigolactones have been revised. This review presents the complete collection of available spectroscopic data of correct structures of strigolactones, the occurrence in plant kingdom, as well as germination and hyphal branching activities, that are of high importance to the scientific community that is investigating these novel plant hormones. Moreover, two new structures of strigolactone members are proposed.