Biosynthesis, functional perspectives, and agricultural applications of strigolactones

Strigolactones (SLs) are carotenoid-derived terpenoid lactones. Natural SLs are grouped into two types, namely, strigol-type and orobanchol-type, and 20 SLs have been identified from different plant kingdoms or species. The more stable SLs, called GR24, derived synthetically, were utilized for the investigation of SL responses. SLs are crucial endogenous plant hormones that play a multifactorial role in plant and rhizosphere interactions by controlling mycorrhization and lateral shoot branching. SLs participate in the organization of plant architecture by reducing bud outgrowth in addition to various morphological and developmental processes, collectively with other plant growth hormones such as auxins, cytokinins, gibberellins, and abscisic acid. Strigolactones regulate root growth and structure by inhibiting lateral root production and enhancing root hair elongation. Targeted genetic engineering of SL biosynthetic genes leads to potential alterations in rooting and vegetative systems and assists in generating plants that are more appropriate to different adverse environmental conditions, such as drought, salt stress, cold, and water deficit. The present review provides a clear outline of the structure, type, biosynthesis, and signaling mechanisms of SLs. In addition, their potential functions in plant growth, development, and response to stress conditions are also discussed.