Heterosis-associated gene expression in early development

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There is emerging evidence that differential gene expression between hybrids and their inbred parents is associated with heterosis and that these altered expression pattern are connected with allele-specific silencing. An important step towards the understanding of this phenomenon would be the knowledge which genes facilitate the identification of differential expressed genes. The first step will be the construction of glass microarrays with cDNAs enriched for differential expressed genes between hybrids and the corresponding inbred lines by supression substractive hybridization. Because expression patterns are established early after fertilization cDNAs representing active genes or stored transcripts of female gametes will be included in these arrays. For expression profiling of hybrids and their inbred parents unigene microarrays will be used in addition to comprehend expression data of as much genes as Early stages of embryo and endosperm development, a few days after fertilization, will be microdissected and used for comparative microarray hybridization between hybrids and the corresponding inbred parents. Comparison of reciprocal F1 hybrids will provide a system to identify genes associated with parentof-origin effects. Very early developmental stages will be profiled to facilitate the identification of genes involved in cell fate determination and constitution of differential expression patterns. Additional profiling of non-pollinated ovules will integrate the mother tissue to provide a more comprehensive view on gene expression related to grain These expression profiles will serve as a basis to clone genes for functional analysis and exploration of gene regulatory networks associated with heterosis.