Engineering Biomimetic Sporangia in Land Plants.

The land plant sporangium is unique in its ability to initiate differentiation of the reproductive germ line, leading directly to meiosis and the formation of eggs and sperm; but our lack of understanding of the processes underlying gametogenesis in plants remains a major obstacle in our ability to modify the sexual cycle for the benefit of crop science. Here we report an initial attempt to create an engineered structure which, with further development, could reproduce the physical and mechanical properties of the land plant sporangium. While the work reported here does not achieve the ultimate goal of in vitro gametogenesis, we do believe it represents a significant step towards understanding the stress-mechanical environment of the land plant sporangium and its role in initiating reproductive development. The immediate goal of this work is to extend the range of experimental methods and tools available for the study of the physical environment of plant cell growth. We describe an experimental protocol based on the microfluidic encapsulation of living plant protoplasts in multilayered microbeads composed of actively tunable hydrogel materials whose properties can be modified to mimic the stress-mechanical behaviors of the living sporangium. Our results demonstrate the first successful encapsulation of a living plant protoplast in dual-layered microbeads consisting of an inner layer of gelled agarose and an outer layer of crosslinked alginate/methacrylate.