Photosynthetic Antenna Engineering to Improve Crop Yields

A genetic tendency of photosynthetic organisms to assemble large arrays of light-absorbing chlorophyll antenna molecules in their photosynthetic apparatus is a survival strategy and a competitive advantage in the wild, where light is often limiting. Competition and survival in the wild requires capturing more light for self, even if in excess of what is needed to saturate photosynthesis and eventually wasted, and preventing light capture by competing neighbors. This competitive survival strategy is detrimental to production-type monocultures under bright sunlight, where over-absorption of photons by the upper canopy, and wasteful dissipation of the excess absorbed energy, are undesirable. Under bright sunlight, more than 80% of absorbed photons can thus be wasted, reducing photon use efficiencies and photosynthetic productivity to undesirably low levels. The work examines the theoretical maximum of solar energy conversion efficiency and productivity in photosynthetic systems. This will be contrasted with actual measurements of substantially lower efficiencies in a variety of photosynthetic organisms, including crop plants. Engineering a Truncated Light-harvesting Antenna size (TLA) in crop plants, where the number of chlorophyll molecules in the photosynthetic apparatus is genetically limited helps to alleviate excess absorption of sunlight and the ensuing wasteful dissipation of excitation energy, and to maximize solar-to-product energy conversion efficiency and photosynthetic productivity in high-density canopies of crop plants. A two-year study with wild type and TLA-tobacco as the model plant has shown TLA-tobacco biomass productivity greater by about 25% over that measured with the wild type under the same climatic and agronomic growth conditions. Thus, application of the TLA concept in the commercial exploitation of crop plants promises to improve growth and biomass accumulation, positively impacting crop yield, as well as plant-derived fuel, synthetic chemistry, and pharmaceutical feedstock production.