GENETIC IMPROVEMENT OF FRUIT CROPS THROUGH FUNCTIONAL GENOMICS AND BREEDING
Location: Appalachian Fruit Research Laboratory: Innovative Fruit Production, Improvement and Protection
Title: Petunia AGAMOUS enhancer-derived chimeric promoters specify a carpel-, stamen- and petal-specific expression pattern sufficient for engineering male and female sterility in tobacco
Submitted to: Plant Molecular Biology Reporter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 12, 2010
Publication Date: June 3, 2010
Citation: Yang, Y., Singer, S., Liu, Z. 2010. Petunia AGAMOUS enhancer-derived chimeric promoters specify a carpel-, stamen- and petal-specific expression pattern sufficient for engineering male and female sterility in tobacco. Plant Molecular Biology Reporter. DOI 10.1007/s11105-010-0215-z
Interpretive Summary: Transgene flow poses a potential risk for the creation of unwanted super or invasive weeds. One of the most effective ways to control gene flow is to incorporate sterility into transgenic plants so that seed-, fruit-, and pollen-mediated gene transfer can be completely prevented. In this study, we isolated and characterized a flower-specific promoter that is capable of inducing male and female sterility in plants. This work provides a new tool for engineering plant sterility and remedying the problems associated with gene flow in transgenic crops.
Previous studies have shown that the AtAGIP promoter derived from the Arabidopsis AGAMOUS (AG) second intron/enhancer specifies a carpel- and stamen-specific pattern of expression in its native host species but not in heterologous species, such as tobacco which restricts its application in the engineering of male and female sterility. These findings also imply that the AG regulatory mechanism that has evolved in Arabidopsis may, to some extent, have diverged from that of tobacco. To test whether a similar chimeric promoter created using the AG second intron/enhancer can overcome this barrier of evolutionary divergence in closely related species, we generated forward- and reverse-oriented chimeric promoters, fPtAGIP and rPtAGIP, from the petunia AG second intron/enhancer (PtAGI) fragment. We also tested them in tobacco. Like petunia, it belongs to the Solanaceae family. Our results demonstrate that both fPtAGIP and rPtAGIP confer similar carpel- and stamen-specific expression without any leaky activity in vegetative tissues in tobacco as revealed by tissue-specific gene expression and tissue ablation. This pattern resembles that driven by the AtAGIP in Arabidopsis and indicates that the AG regulatory mechanism is more conserved between tobacco and petunia than between tobacco and Arabidopsis. The petunia-derived promoters also exhibited petal-specific activity and their activities were substantially influenced by the orientation of the PtAGI enhancer with reverse-oriented enhancers displaying approximately double the effectiveness of forward-oriented enhancers. These two properties have not been observed previously with AtAGIP promoters. Furthermore, we found that PtAGIP promoter-driven tissue ablation is effective for engineering complete sterility in plants, and the resulting sterile trait is stable for at least three mitotic generations at various temperature regimes, which is important for the complete containment of seed-, pollen- and fruit-mediated gene flow in field conditions.