Poster: Reproductive development

Abs # 348: Function of the acetyl-CoA carboxylase1 gene in the development of ovules and seeds of Arabidopsis

Presenter:	Ilarslan, Hilal I, ihilal@iastate.edu
Authors	Ilarslan, Hilal I (A)   Schmidt, Joel  (B)   Nikolau, Basil J (B)   Wurtele, Eve S (A)
Affiliations:	(A): Iowa State University, Department of Genetics, Development and Cell Biology (B): Iowa State University, Biochemistry, Biophysics and Molecular Biology

Homomeric acetyl-CoA carboxylase (ACCase), encoded by the ACC1 gene, is a cytosolic enzyme that catalyzes the formation of malonyl-CoA required for the synthesis of a variety of phytochemicals including flavonoids, cuticular waxes, and malonylated derivatives. The ACC1 gene is expressed in a cell-specific manner throughout development, including in flowers and embryos. Genetic analysis of two SALK-derived, T-DNA-tagged acc1 alleles indicate that homomeric ACCase derived from the ACC1 gene is essential for the formation of viable seeds. Self-fertilization of individual plants heterozygous for such acc1 mutations results in the recovery of ACC1/ ACC1 and ACC1/acc1 progeny only in an approximately 2:1 ratio, as indicated by genotyping of the F1 progeny. This inability to recover acc1/acc1 plants indicates that the acc1 mutation is lethal. To further investigate the morphological consequence of the absence of ACC1 expression in the embryo, light and confocal scanning laser microscopy were conducted on developing siliques. Approximately 1/4 of the ovules in mature siliques have partially-developed ovules or remnants of seed coats that are either empty, or only contain several embryonic cells, indicating an early block to embryo development. Examination of the female gametophyte and post-pollination development of the embryo by confocal microscopy indicates that fertilization and development of the ovule is normal. Embryos, however, are arrested at the globular stage of development, and endosperm development ceases concomitantly. Despite the arrest in embryo and endosperm development, the surrounding maternal tissue sometimes deposits a shriveled seed coat. These data indicate that the ACC1 gene is essential for early embryo development.