The PsEND1 promoter:: a novel tool to produce genetically engineered male-sterile plants by early anther ablation

PsEND1 is a pea anther-specific gene that displays very early expression in the anther primordium cells. Later on, PsEND1 expression becomes restricted to the epidermis, connective, endothecium and middle layer, but it is never observed in tapetal cells or microsporocytes. We fused the PsEND1 promoter region to the cytotoxic barnase gene to induce specific ablation of the cell layers where the PsEND1 is expressed and consequently to produce male-sterile plants. Expression of the chimaeric PsEND1::barnase gene in two Solanaceae (Nicotiana tabacum and Solanum lycopersicon) and two Brassicaceae (Arabidopsis thaliana and Brassica napus) species, impairs anther development from very early stages and produces complete male-sterile plants. The PsEND1::barnase gene is quite different to other chimaeric genes previously used in similar approaches to obtain male-sterile plants. The novelty resides in the use of the PsEND1 promoter, instead of a tapetum-specific promoter, to produce the ablation of specific cell lines during the first steps of the anther development. This chimaeric construct arrests the microsporogenesis before differentiation of the microspore mother cells and no viable pollen grains are produced. This strategy represents an excellent alternative to generate genetically engineered male-sterile plants, which have proved useful in breeding programmes for the production of hybrid seeds. The PsEND1 promoter also has high potential to prevent undesirable horizontal gene flow in many plant species.