Synthetic Strigolactone GR24 Improves Somatic Embryogenesis through Changes in Auxin Responses.

Somatic embryogenesis in encompasses an induction phase requiring auxin as the inductive signal to promote cellular dedifferentiation and formation of the embryogenic tissue, and a developmental phase favoring the maturation of the embryos. Strigolactones (SLs) have been categorized as a novel group of plant hormones based on their ability to affect physiological phenomena in plants. The study analyzed the effects of synthetic strigolactone GR24, applied during the induction phase, on auxin response and formation of somatic embryos. The expression level of two SL biosynthetic genes, and and ), which are responsible for the conversion of carotene to carotenal, increased during the induction phase of embryogenesis. mutant studies indicated that the somatic embryo number was inhibited in and mutants, and this effect was reversed by applications of GR24, a synthetic strigolactone, and exacerbated by TIS108, a SL biosynthetic inhibitor. The transcriptional studies revealed that the regulation of GR24 and TIS108 on somatic embryogenesis correlated with changes in expression of known to be required for the production of the embryogenic tissue, as well as the expression of () and (), which are markers of cell dedifferentiation and embryogenic tissue formation. Collectively, this work demonstrated the novel role of SL in enhancing the embryogenic process in and its requirement for inducing the expression of genes related to auxin signaling and production of embryogenic tissue.