Analysis of gene copy number variation in the asexual Boechera holboellii complex (Brassicaceae)

• Applicant: Professor Dr. Timothy Sharbel
• Subject Area: Plant Genetics and Genomics
• Term: from 2008 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 98137465

In plants, the expression of gametophytic apomixis (asexual reproduction through seed) requires the coordination of three independent mechanisms: (1) production of an unreduced embryo sac (apomeiosis); (2) the parthenogenetic development of the embryo in the absence of fertilization; and (3) the fertilization (pseudogamy) and production of a functional endosperm. We have recently completed a deep gene expression analysis of apomeiosis (unreduced gamete formation) in the genus Boechera, a wild relative of Arabidopsis in which the rare condition of diploid apomixis is found. This approach has enabled us to identify over 4000 differentially-expressed genes between sexual and apomeiotic ovules at a single stage of development. The expression patterns of these genes were reflective of three mechanisms: (a) shifts in gene expression timing between sexual and apomeiotic ovules, (b) allele-specific expression in a hybrid genome (parent of origin effect), and (c) microduplication (copy number variation) in the apomictic genome. In the following project description, we propose to examine the third mechanism, microduplication (gene copy number variation). Apomictic Boechera have arisen through hybridization, and our data show that upregulation of genes in apomeiotic ovules is mediated by microduplication. Considering that hybridization is a mechanism through which microduplication could be induced, we propose an analysis of copy number variation for all differentially-expressed genes which we have previously identified, using crosses between different Boechera accessions.

• DFG Programme: Research Grants