Four goes into three

When it comes to fixing carbon, crop plants such as rice are at a distinct disadvantage. They use the C₃ photosynthetic pathway, which is much more sensitive to O₂ inhibition than plants that directly produce C₄ dicarboxylic acids from CO₂ via an enzyme called phophoenolpyruvate carboxylase (PEPC). In this issue, researchers have successfully transformed rice with the PEPC gene from the C₄ plant maize. While this represents a preliminary step in engineering a C ₄ pathway, introduction of the PEPC transgene into rice was sufficient to reduce O₂ inhibition of photosynthesis compared with wild-type plants (see pp. 22 and 76).