Exploiting leaf starch synthesis as a transient sink to elevate photosynthesis, plant productivity and yields

Improvements in plant productivity (biomass) and yield have centered on increasing the efficiency of leaf CO2 fixation and utilization of products by non-photosynthetic sink organs. We had previously demonstrated a correlation between photosynthetic capacity, plant growth, and the extent of leaf starch synthesis utilizing starch-deficient mutants. This finding suggested that leaf starch is used as a transient photosynthetic sink to recycle inorganic phosphate and, in turn, maximize photosynthesis. To test this hypothesis, Arabidopsis thaliana and rice (Oryza sativa L.) lines were generated with enhanced capacity to make leaf starch with minimal impact on carbon partitioning to sucrose. The Arabidopsis engineered plants exhibited enhanced photosynthetic capacity; this translated into increased growth and biomass. These enhanced phenotypes were displayed by similarly engineered rice lines. Manipulation of leaf starch is a viable alternative strategy to increase photosynthesis and, in turn, the growth and yields of crop and bioenergy plants.

► In this manuscript, we increased the flow of fixed carbon into leaf starch.
► Arabidopsis thaliana and rice plants expressing this mutant enzyme have higher starch turnover levels during the diurnal cycle.
► Such plants showed increased photosynthesis, plant growth and seed yields.
► These results conclusively demonstrate that the photosynthetic capacity of plants is much lower than optimum because of photosynthetic feedback.
► Starch can be used as a transient sink to increase photosynthetic capacity which will result in increase plant productivity and yields.