Reversible male sterility in eggplant (Solanum melongena L.) by artificial microRNA-mediated silencing of general transcription factor genes.

Since decades, plant male sterility is considered a powerful tool for biological containment to minimize unwanted self-pollination for hybrid seed production. Furthermore, prevention of pollen dispersal also answers to concerns regarding transgene flow via pollen from Genetically Modified (GM) crops to traditional crop fields or wild relatives. We induced male sterility by suppressing endogenous general transcription factor genes, TAFs, using anther-specific promoters combined with artificial microRNA (amiRNA) technology (Schwab et al., 2006). The system was made reversible by the ethanol inducible expression of an amiRNA-insensitive form of the target gene. We provide proof of concept in eggplant, a cultivated crop belonging to the Solanaceae family that includes many important food crops. The transgenic eggplants that we generated are completely male sterile and fertility can be fully restored by short treatments with ethanol, confirming the efficiency but also the reliability of the system in view of open field cultivation. By combining this system with induced parthenocarpy (Rotino et al., 1997), we provide a novel example of complete transgene containment in eggplant, which enables biological mitigation measures for the benefit of coexistence or biosafety purposes for GM crop cultivation.