AnArabidopsis thalianaembryo arrest mutant exhibiting germination potential

Abstract

AbstractThe ability to initiate radicle elongation, or germination potential, occurs in developing embryos before the completion of seed maturation. Green embryos after the walking-stick stage in developingArabidopsis thalianaseeds germinate when excised from seeds and incubated in Murashige–Skoog (MS) medium containing 1% sucrose. Germination potential is not observed during early embryogenesis at the globular, heart and torpedo stages. Here, we describe anArabidopsismutant with embryos arrested at early stages of development, but still exhibiting germination potential. The mutant, termedembryo ball(eb), produced shrunken seeds containing round or irregularly shaped embryos that did not germinate. The round embryos excised from developingebseeds were capable of growing a primary root with root hairs when incubated in media. In contrast, cotyledons were absent at the apical region of theebembryos, although the apical region produced leaf-like structures with trichomes, indicating vegetative leaf identity. These observations suggested that morphological maturation was not essential for the induction of germination potential. Theebembryos exhibited partial desiccation tolerance that is characteristic of mature embryos at later stages of development, suggesting that cell maturation was also independent of morphological maturation. Theebmutant provides novel information on cell and tissue identity in developmental biology, as well as a useful tool to dissect the mechanisms underlying the induction of germination potential in developing seeds.