title: Gene expression analyses in maize inbreds and hybrids with varying levels of heterosis.
abstract: BACKGROUND
  Heterosis is the superior performance of F1 hybrid progeny relative to the parental phenotypes. Maize exhibits heterosis for a wide range of traits, however the magnitude of heterosis is highly variable depending on the choice of parents and the trait(s) measured. We have used expression profiling to determine whether the level, or types, of non-additive gene expression vary in maize hybrids with different levels of genetic diversity or heterosis.
  
  
  RESULTS
  We observed that the distributions of better parent heterosis among a series of 25 maize hybrids generally do not exhibit significant correlations between different traits. Expression profiling analyses for six of these hybrids, chosen to represent diversity in genotypes and heterosis responses, revealed a correlation between genetic diversity and transcriptional variation. The majority of differentially expressed genes in each of the six different hybrids exhibited additive expression patterns, and approximately 25% exhibited statistically significant non-additive expression profiles. Among the non-additive profiles, approximately 80% exhibited hybrid expression levels between the parental levels, approximately 20% exhibited hybrid expression levels at the parental levels and ~1% exhibited hybrid levels outside the parental range.
  
  
  CONCLUSIONS
  We have found that maize inbred genetic diversity is correlated with transcriptional variation. However, sampling of seedling tissues indicated that the frequencies of additive and non-additive expression patterns are very similar across a range of hybrid lines. These findings suggest that heterosis is probably not a consequence of higher levels of additive or non-additive expression, but may be related to transcriptional variation between parents. The lack of correlation between better parent heterosis levels for different traits suggests that transcriptional diversity at specific sets of genes may influence heterosis for different traits.
authors.affiliation: Center for Plant and Microbial Genomics, Department of Plant Biology, University of Minnesota, Saint Paul MN 55108, USA. stup0004@umn.edu
authors.forename: Robert M
authors.initials: RM
authors.lastname: Stupar
authors.forename: Jack M
authors.initials: JM
authors.lastname: Gardiner
authors.forename: Aaron G
authors.initials: AG
authors.lastname: Oldre
authors.forename: William J
authors.initials: WJ
authors.lastname: Haun
authors.forename: Vicki L
authors.initials: VL
authors.lastname: Chandler
authors.forename: Nathan M
authors.initials: NM
authors.lastname: Springer
mesh_terms: D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006823:Hybrid Vigor / Q000235:genetics*; D006824:Hybridization, Genetic; D007178:Inbreeding; D020411:Oligonucleotide Array Sequence Analysis; D003313:Zea mays / Q000235:genetics*