Strigolactones: multi-level regulation of biosynthesis and diverse responses in plant abiotic stresses

Abstract

Strigolactones (SLs) are a small class of diverse metabolites derived from the carotenoid pathway. These active biomolecules are a recent inclusion to the list of non-traditional phytohormones or plant growth regulators. Previous reports and articles have discussed their pro-regulatory roles in plant growth, development, signaling and delay of senescence. However, the multi-level control of SL biosynthesis is less known. The anabolic genes are strictly regulated through synchronized co-operation between crucial phytohormones. Epigenetic and microRNA-mediated post-transcriptional regulation fine tunes the cellular accumulation of these putative phytohormones. The question now arises that why such multi-level intricate regulation at all is required for SLs, which were originally detected as under-rated germination and rhizosphere stimulants. This review answers the question in the backdrop of the positive roles of SLs in promoting abiotic stress resilience across diverse plant species. SLs reportedly accumulate in the plant tissues in response to environmental sub-optimal conditions like drought, salinity, temperature, nutrient deprivation and oxidative stresses. Fluctuations in the light quality and intensity also trigger variable accumulation of SLs, indicating their potential in regulating light stress as well. Though the exact roles of SLs have not yet been characterized, it is predicted that they possibly induce the expression of downstream osmolytes to maintain metabolic homeostasis in the stressed cells. Thus, exogenous treatments or transgenic approaches for higher SL bioaccumulation can be potential strategies for developing multiple abiotic stress tolerance in crops and plants.