Figure 2.

Comparison of additive and nonadditive hybrid expression patterns in endosperm and vegetative tissues. A, The d/a values are plotted for all differentially expressed genes in endosperm tissue. For each differentially expressed gene, the d/a value was calculated for the maternal hybrid relative to the higher expressing parent (e.g. BBM if BBB > MMM) and for the paternal hybrid relative to the higher expressing parent (e.g. MMB if BBB > MMM). The expected values for additive expression are 0.33 for the maternal hybrid and −0.33 for the paternal hybrid. Black symbols indicate the values for the maternal hybrid and gray symbols indicate the values for the paternal hybrid. Symbol shape indicates the tissue stage. B, A similar plot for d/a values is presented for seedling and immature ear vegetative tissues. Due to the equal dosage of the two parental genomes, the expected values for additive expression are 0.0 for both the maternal and paternal hybrids. C, A scatter plot of d/a expression values from reciprocal hybrids in endosperm (gray spots) and vegetative (black spots) tissues shows the density and range of nonadditive expression among tissue types. Each spot represents the d/a value of a gene for the two reciprocal hybrids. The y axis represents d/a values of the maternal hybrid of the HP and the x axis represents d/a values of the paternal hybrid of the HP. The approximate position of the additive and nonadditive classes in this display is indicated by the text. Values that plot within the black square represent genes in which both hybrids exhibit expression levels within the parental range. Genes for which both hybrids display AHP or BLP expression would plot in the top right and bottom left quadrants. Genes exhibiting parent-of-origin effects on hybrid expression will plot in the top left and bottom right quadrants. A small portion of the data plotted outside the range of the graph and is therefore not shown in this display.