Altered Promoter and G-Box Binding Factor for 1-Deoxy-d-Xylulose-5-Phosphate Synthase Gene Grown from Poa pratensis Seeds after Spaceflight

In plant cells, the nucleus DNA is considered the primary site of injury by the space environment, which could generate genetic alteration. As the part of genomic mutation, genetic variation in the promoter region could regulate gene expression. In the study, it is observed that there is a deletion in the upstream regulatory region of the 1-deoxy-d-xylulose-5-phosphate synthase 1 gene (PpDXS1) of Poa pratensis dwarf mutant and the PpDXS1 transcript abundance is lower in the dwarf mutant. It is indicated that the deletion in the promoter region between wild type and dwarf mutant could be responsible for the regulation of PpDXS1 gene expression. The PpDXS1 promoter of dwarf mutant shows a lower activity as determined by dual luciferase assay in Poa pratensis protoplast, as well as the GUS activity is lower in transgenic Poa pratensis plant. To further investigate the effect of the deletion in the promoter region on PpDXS1 transcript accumulation, the transient assay and yeast one-hybrid experiment demonstrate that the deletion comprises a motif which is a target of G-box binding factor (GBF1), and the motif correlates with an increase in transactivation by GBF1 protein. Taken together, these results indicate that the deletion in the promoter of PpDXS1 isolated from dwarf mutant is sufficient to account for the decrease in PpDXS1 transcript level and GBF1 can regulate the PpDXS1 gene expression, and subsequently affect accumulation of various isoprenoids throughout the plant.