a1 Department of Horticulture, Oregon State University, Corvallis, OR 97331, USA
a2 Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA
a3 Department of Microbiology, Oregon State University, Corvallis, OR 97331, USA
a4 US Department of Agriculture, Agricultural Research Service, National Forage Seed Production Research Center, 3450 SW Campus Way, Corvallis, OR 97331-7102, USA
The 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 developing Arabidopsis thaliana seeds 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 an Arabidopsis mutant with embryos arrested at early stages of development, but still exhibiting germination potential. The mutant, termed embryo ball (eb), produced shrunken seeds containing round or irregularly shaped embryos that did not germinate. The round embryos excised from developing eb seeds were capable of growing a primary root with root hairs when incubated in media. In contrast, cotyledons were absent at the apical region of the eb embryos, 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. The eb embryos 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. The eb mutant 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.
(Received June 13 2007)
(Accepted February 26 2008)
p1 Synthetic Genomics, Inc., La Jollas, CA 92037, USA.
p2 Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853 USA.
p3 The Vollum Institute, Oregon Health & Science University, L474, 3181 SW, Sam Jackson Park Road, Portland, OR 97239-3098, USA.