Structural Chemistry, Biosynthesis, and Signaling of Multifaceted Plant Growth Regulator: Strigolactone.

Plants being mostly sessile are exposed to several adverse environmental conditions. Many endogenous and exogenous factors play a vital role in acclimatizing plants in such varying environments. Plant growth regulators (PGRs) are one such endogenous factor that regulates the phenomenon of growth and development in plants. Strigolactone (SL) has been accepted as a new class of phytohormones or PGRs. It has contributed to different aspects of plant growth and development such as root growth and shoot branching as well as the response of plants to several biotic and abiotic stresses. Lately, a deep understanding of the SL biosynthetic pathway has been revealed. Transcriptomics and genetic analysis showed that SLs are derived from an intermediate carotenoid biosynthesis pathway, all-trans-β-carotene. Carlactone (CL) is formed from all-trans-β-carotene by the subsequent action of a set of core enzymes DWARF27 (D27), and carotenoid cleavage dioxygenases (CCD7 and CCD8). CL is the ultimate biosynthetic precursor of all naturally occurring SLs. The investigation has been also carried out on signal perception and downstream cascade involved in SL signaling by utilizing various mutants from different plant species. D14, AtD14, and DAD2 are identified as orthologous SL receptors of Oryza sativa, Arabidopsis thaliana, and Petunia, respectively. These are identified as αβ hydrolase, having the activity of both receptor and enzyme. The present review summarizes the current perception of the nature and biosynthesis of SL and the deciphering of the mechanism involved in its signal transduction cascade. [ABSTRACT FROM AUTHOR]