10 - Strigolactones

Abstract

Strigolactones (SLs) are carotenoid-derived signaling molecules and plant hormones that enable root-parasitic plants and symbiotic fungi to detect their host plants. They also regulate several developmental processes that adapt shoot and root architecture to the environment. Highly branching or tillering mutants in Arabidopsis thaliana petunia, pea, and rice have greatly facilitated the identification of SL biosynthetic enzymes and signaling components. The carotenoid precursor undergoes isomerization and cleavage to generate carlactone, which then undergoes oxidation and further modification to produce a range of strigolactone structures. Perception of SLs involves a novel mechanism in which a serine hydrolase-type enzyme receptor attacks the SLs and becomes covalently modified. This triggers the interaction of the receptor with other proteins including an F-box protein, leading to ubiquitination and destruction of target proteins such as transcriptional regulators. In this chapter, we introduce the discovery of SLs, summarize progress in understanding the SL biosynthesis, transport of SLs, and their signaling pathway. We also highlight their functions in plant development, symbiosis, and parasitism, as well as the cross talk with environmental signals and other phytohormones.