Development of an mPing-based Activation Tag for Crop Insertional Mutagenesis

Modern plant breeding increasingly relies on genomic information to guide crop improvement. Although some genes are characterized, additional tools are needed to effectively identify and characterize novel genes associated with crop traits. To meet this need, the mPing element from rice was developed as an activation tag designed to induce overexpression of nearby genes. Addition of promoter sequences to mPing resulted in a decrease in overall transposition rate, however, this effect was negated by using a hyperactive version of mPing called mmPing20. These mPing-based activation tags were found to induce expression of nearby reporter genes in transient assays. Transgenic soybean plants carrying mPing-based activation tags and the appropriate transposase protein expression constructs showed evidence of transposition. Expression analysis of a line that contained a heritable insertion of the mmPing20F activation tag, indicated that the activation tag induced overexpression of the nearby soybean genes. This represents a significant advance in gene discovery technology as activation tags have the potential to induce more phenotypes than the original mPing element, improving the overall effectiveness of the system. Two replicates of plants harboring the mPing based activation tag (T162821 and T162822) were compared with two plants not harboring the activation tag. The latter two plants consisted of an untransformed soybean plant (Thorne) and a transgenic plant containing the transposase expression construct (T1622845).