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GENETICS, GENOMICS, AND MOLECULAR EVOLUTION

Nonadditive Expression and Parent-of-Origin Effects Identified by Microarray and Allele-Specific Expression Profiling of Maize Endosperm^1,[W],[OA]

Center for Plant and Microbial Genomics, Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108

Plant endosperm cells have a nuclear ratio of two maternal genomes to one paternal genome. This 2 to 1 dosage relationship provides a unique system for studying the additivity of gene expression levels in reciprocal hybrids. A combination of microarray profiling and allele-specific expression analysis was performed using RNA isolated from endosperm tissues of maize (Zea mays) inbred lines B73 and Mo17 and their reciprocal hybrids at two developmental stages, 13 and 19 d after pollination. The majority of genes exhibited additive expression in reciprocal hybrids based on microarray analyses. However, a substantial number of genes exhibited nonadditive expression patterns, including maternal like, paternal like, high parent like, low parent like, and expression patterns outside the range of the parental inbreds. The frequency of hybrid expression patterns outside of the parental range in maize endosperm tissue is much higher than that observed for vegetative tissues. For a set of 90 genes, allele-specific expression assays were employed to monitor allelic bias and regulatory variation. Eight of these genes exhibited evidence for maternally or paternally biased expression at multiple stages of endosperm development and are potential examples of differential imprinting. Our data indicate that parental effects on gene expression are much stronger in endosperm than in vegetative tissues.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Nathan M. Springer (springer{at}umn.edu).

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.101428

^* Corresponding author; e-mail springer{at}umn.edu.

Received April 23, 2007; accepted August 24, 2007; published August 31, 2007.