Strigolactone

Strigolactones are a group of chemical compounds produced by roots of plants. Due to their mechanism of action, these molecules have been classified as plant hormones or phytohormones. So far, strigolactones have been identified to be responsible for three different physiological processes: First, they promote the germination of parasitic organisms that grow in the host plant's roots, such as Striga lutea and other plants of the genus Striga. Second, strigolactones are fundamental for the recognition of the plant by symbiotic fungi, especially arbuscular mycorrhizal fungi, because they establish a mutualistic association with these plants, and provide phosphate and other soil nutrients. Third, strigolactones have been identified as branching inhibition hormones in plants; when present, these compounds prevent excess bud growing in stem terminals, stopping the branching mechanism in plants.

Strigolactones comprise a diverse group, but they all have core common chemical structure, as shown in the image to the right. The structure is based on a tricyclic lactone linked to a hydroxymethyl butenolide; the former is represented in the figure as the A-B-C part, while the latter is the D part of the molecule. Most strigolactones present variations in the ABC part, but the D ring is quite constant across the different species, which led researchers to suspect that the biological activity relies on this part of the molecule. Different studies have demonstrated that the activity of the molecules is lost when the C-D section of the molecules is modified.

Since strigolactones are involved in the signaling pathway required for germination of parasitic species (such as Striga sp.), they have been a proposed target to control pests and overgrowth of these parasitic organism. Using a molecule similar to strigolactones could be the key to designing a chemical and biological mechanism to stop the colonization of a plant's root by parasitic plants.