Identification of genes specifically expressed in androgenesis-derived embryo in rapeseed (Brassica napus L.)

Microspore culture is an efficient system to produce haploid and double-haploid plants, and is a useful model system in developmental research. Although many studies have been carried out to understand the mechanism of microspore embryogenesis, the details of molecular events occurring during its developmental process are unclear. During embryogenesis, a marked morphological change occurs just after globular stage embryos. To gain insight into the developmental process of androgenesis in rapeseed (Brassica napus), we isolated the genes expressed differentially during globular stage by suppression subtractive hybridization (SSH). Of 254 ESTs isolated and sequenced, 82 were singletons and the remaining 172 were assembled into 28 groups based on homology to the identical gene, resulting in the identification of 110 non-redundant EST groups, which are potentially up-regulated genes in androgenesis. Survey of the potential function of the genes showed that 96.4% of these genes were homologous to known genes with 42.7% of unclassified proteins and 13.6% of metabolism. To confirm the expression profiles of isolated genes during androgenesis and zygotic embryogenesis, six selected genes were examined by quantitative RT-PCR analysis. All genes were highly expressed in globular and other stages of androgenesis. The expressions of these genes were confirmed in zygotic embryogenesis. These results serve as a starting point for understanding the mechanism of androgenesis and zygotic embryogenesis.