Pro­duc­tion of the major crops must in­crease at least 50% by 2050 to feed a grow­ing world popu­lation. While classi­cal breed­ing tech­niques may not achieve this goal, syn­thetic biolo­gy and meta­bolic engi­neer­ing hold the poten­tial to deliv­er new tools and tech­nolo­gy to im­prove yield. We use di­rected evolu­tion to engi­neer car­bon avail­ability in plants by in­creas­ing CO2 fixa­tion and de­creas­ing respi­ration.

Plants need car­bon, nitro­gen and other nutri­ents to grow. Dur­ing evolu­tion, they evolved under nutri­ent-limiting and car­bon-surplus condi­tions be­cause CO2 has al­ways been avail­able which they fix from the at­mosphere. It is likely that evolu­tion has not yet achieved opti­mal car­bon fixa­tion and usage be­cause other nutri­ents (e.g. nitro­gen) have been lim­ited any­ways. In mod­ern agri­cul­tural prac­tices, the sur­plus of car­bon over other nutri­ents has turned to the oppo­site as plants are ferti­lized and irri­gated in the field. Thus, mod­ern crops are car­bon-limited which re­stricts yield.