Expression analysis of maize opaque2 mutants and Glu-1Dx5 transgenic corn
The maize (Zea mays L.) opaque2 (o2) mutant has high lysine content, but soft and starchy kernels. We confirm that Lys content, kernel density, and reduction of zein proteins in o2 mutants are genetic-background dependent. Microarray analysis was carried out by pooling the same amount of mRNA from eight o2 lines to probe the maize Unigene cDNA chip to understand the o2 main effects. 202 genes identified as differentially expressed fit our definition of main effect genes. Comparative analysis of the expression profiles of two additional inbred lines shows that B46WT/B46 o2 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.;To better understand the O2 regulatory network in maize endosperm, temporal profiling of differences in endosperm transcript levels between the maize inbred lines B45 and B45o2 was conducted at four time points during endosperm development. The differentially expressed genes possibly involved in the same pathway were grouped together. Analysis of the promoter region of a basic leucine zipper gene identified as differentially expressed and clustering of this gene into the same group as o2 gene suggest it may be directly regulated by O2. Two putative G-box binding protein genes found to be up-regulated in the o2 mutant may act as transcriptional repressors in the 02 regulatory network.;In the third study, we set out to transform a wheat Glu-1Dx5 gene potentially regulated by O2 into corn to manipulate the protein content of maize endosperm. The levels of transgene expression and zein contents were quantified. Additionally, the zein levels were significantly lower in endosperm containing Glu-1Dx5 in event 190. No substantial changes in the global gene expression pattern suggest that it is possible to transfer genes between species and have it highly expressed without causing big perturbations to the native host system.