Facilitated Initiation of Somatic Embryogenesis in Arabidopsis Thaliana by Mutations in Genes Repressing Meristematic Cell Divisions

Abstract

A very efficient and reproducible system for somatic embryogenesis in Arabidopsis was established by using intact seedlings of the primordia timing mutant (pt). Embryogenie clusters originated from the enlarged shoot apical meristem (SAM) of the mutant seedlings when germinated in 2,4-D containing liquid media, pt somatic embryos had all characteristic embryo pattern elements, but with higher and more variable numbers of cell layers and cells per cell layer. This finding shows that pattern formation can be completed in somatic embryos without the regular cell division pattern seen in zygotic embryos. Embryogenie cell lines were also established from seedlings of other mutants with enlarged SAMs, such as clavatal and clavata3 (civ), pt civ 1-4 and pt clv3-2 double mutants showed additive effects on SAM size and an even higher frequency of seedlings producing embryogenie cell lines. This data suggest that an increased population of noncommitted SAM cells may be responsible for facilitated establishment of somatic embryogenesis in Arabidopsis.