Biologists may have unearthed the potential to manipulate the functions of chloroplasts, the parts of plant cells responsible for photosynthesis. Researchers discovered that chloroplasts are affected by the ubiquitin proteasome system (UPS) — a process which causes the breakdown of unwanted proteins in cells. As a result, the researchers believe they may be able to use specific proteins to regulate the functions of chloroplasts — such as the conversion of chloroplasts into highly-pigmented chromoplasts during the ripening of fruit.