Gene Expression Profiling Reveals Transcription Factor Networks and Subgenome Bias During Brassica Napus Seed Development

We profiled the global gene expression landscape across the reproductive lifecycle of Brassica napus. Comparative analysis of this nascent amphidiploid revealed the contribution of each subgenome to plant reproduction. Whole-genome transcription factor networks identified BZIP11 as a transcriptional regulator of early B. napus seed development. Knockdown of BZIP11 using RNA interference resulted in a similar reduction in gene activity of predicted gene targets, and a reproductive-lethal phenotype. Global mRNA profiling revealed lower accumulation of C subgenome transcripts relative to the A subgenome. Subgenome-specific transcription factor networks identified distinct transcription factor families enriched in each of the A and C subgenomes early in seed development. Analysis of laser-microdissected seed subregions further reveal subgenome expression dynamics in the embryo, endosperm and seed coat of early stage seeds. Transcription factors predicted to be regulators encoded by the A subgenome are expressed primarily in the seed coat, whereas regulators encoded by the C subgenome were expressed primarily in the embryo. Data suggest subgenome bias are characteristic features of the B. napus seed throughout development, and that such bias might not be universal across the embryo, endosperm and seed coat of the developing seed. Transcriptional networks spanning both the A and C genomes of the whole B. napus seed can identify valuable targets for seed development research and that -omics level approaches to studying gene regulation in B. napus can benefit from both broad and high-resolution analyses.