Expression analysis of maize opaque2 mutants and Glu-1Dx5 transgenic corn

Abstract

The maize (Zea mays L.) opaque2 (o2) mutant has high lysine content, but soft and starchy kernels. The o2 pleiotropic effects depend on its genetic background. To characterize the effects of the genetic background on the o2 mutant, the amino acid content and the kernel density of eight pairs of wild-type and o2 inbred lines were analyzed. Our results confirm that the Lys content and the kernel density of o2 mutants from the eight inbred lines are genetic-background dependent. Moreover, the differences of Lys content are negatively correlated with the differences of kernel density between wild-type and o2 mutant. Further analysis of zein protein levels in two pairs of inbred lines, B46WT/o2 and M14WT/o2, with the most and least difference of Lys content between wild-type and o2 reveals that the extent of reduction of zein contents is also dependent on its geneticbackground. In order to understand the main effects of o2 mutation which are masked by its genetic background at transcript level, microarray analysis was carried out by pooling the same amount of mRNA from eight o2 lines to probe the maize Unigene cDNA chip. Additional two inbred lines with most and least extreme phenotypes were investigated separately. 202 genes identified as differentially expressed in the comparison of eight pooled inbred lines fit our definition of main effect genes. Comparative analysis of the expression profiles of B46WT/B46o2, M14WT/M14o2, and Pooled WT/o2 from eight genetic lines shows B46WT/B46o2 with the most extreme phenotype has the highest extent of differential expression and the largest number of genes being affected by o2 mutation. Further analysis of o2 gene expression suggests that the genetic background effect is correlated to the transcript level of o2.