Partial Degeneration Of Cell Clusters During Carrot Somatic Embryogenesis And Gene Involved In Degeneration

Abstract

Carrot somatic embryos are directly formed when hypocotyls are briefly treated with 2,4-D and then cultured in hormone-free medium. We are interested in morphological events of cell cluster to globular embryo in embryo-forming process. In serial observation of somatic embryogenesis, we found that a part of cell cluster developed into embryo, whereas another was degenerated. Furthermore, we isolated a gene that may be probably involved in a partial degeneration of cell cluster. This gene, named 'nucellin-like protein' has similarity to barley nucellin (Chen et al., 1997) that encodes aspartic protease and may be involved in death of nucellar cell surrounding the entire embryo sac after pollination. Northern analysis revealed that nucellin-like protein transcripts were highly detected in cell clusters and slightly in globular embryos, but hardly in heart- and torpedo-shaped embryos and plantlets.