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Unraveling the auxin mechanism in 2,4-D induced somatic embryogenesis in Arabidopsis thaliana

Promotor: P. J. J. Hooykaas, Co-promotor: R. Offringa

Cheryl Philipsen
30 March 2017
Thesis in Leiden Repository

Plant clonal propagation can be achieved through shoot- and root regeneration. Alternatively, it can be induced by somatic embryogenesis (SE). In Arabidopsis thaliana, somatic embryos are efficiently induced by incubating immature zygotic embryos (IZEs) on SE induction medium (SEIM) containing high concentrations of the auxin analogue 2,4-dichlorophenoxyacetic acid (2,4-D). During SE somatic cells are reprogrammed to become totipotent cells, from which a new embryo cell fate is acquired in order to develop somatic embryos. The genetic and molecular mechanism by which 2,4-D induces SE initiation has not been elucidated yet and the aim of this PhD thesis was to identify which components of the auxin response pathway are involved in this developmental process. It is proposed that lateral root initiation is similar to SE initiation in that an auxin maximum followed by a minimum is required for both processes, and that the auxin responses in both systems are modulated by the same SLR/IAA14 module. Substantial work is still required to outline the details of downstream responses. They possibly include the regulation of auxin biosynthesis through TAA1/TAR and the coordinated expression of AUX1/LAX proteins to establish the dynamic auxin response leading to SE initiation.