Come together: Intein-mediated protein ligation in transgenic wheat

We describe the results of previous studies (Gils et al., 2008, Kempe et al., 2009, Kempe et al., in press) aimed at optimizing split-gene expression systems in wheat. Introns from Petunia hybrida and Arabidopsis thaliana were used to enhance the tapetum-specific expression of a split barnase transgene. The barnase fragments were assembled into a functional cytotoxin via intein-mediated trans-splicing, leading to male sterility by pollen ablation. Additionally, the effect of introducing multiple GGGGS peptide linkers on the efficiency of protein assembly was examined. Constructs carrying different combinations of introns and peptide linkers were transformed into wheat plants. Depending on the construct, there was up to a five-fold increase in the proportion of plants exhibiting male sterility compared to the populations harboring unmodified constructs. Furthermore, the average barnase copy number could be reduced in plants displaying the desired phenotype.