Genetic manipulation of miR156 for improvement of biomass production and forage quality in red clover

Red clover (Trifolium pratense L.) is an important forage legume in the United States. Improving forage quality and biomass yield is an important goal of forage breeding programs. Plant development, particularly the transition from vegetative to reproductive growth, is an important factor affecting biomass accumulation and forage quality. Thus, genetic manipulation of genes that regulate the transition from the vegetative to reproductive phase can be an efficient strategy for genetic improvement of red clover. One such gene is miR156, a microRNA gene that serves as a master regulator of vegetative phase change in land plants. We report here the development of transgenic red clover plants overexpressing the maize Corngrass1 gene encoding two tandem miR156s. The transgenic plants displayed striking phenotypic changes compared with the wild-type plants, including the increased number of shoots, delayed flowering, enhanced forage yield, and improved forage quality. These results suggest that manipulating miR156 or its target genes is a potential tool for genetic improvement of forage legumes.