The enzyme that makes cutin, a polymer found in plant skins, is reported in an article published online this week in Nature Chemical Biology. These findings will have an impact on plant research and could be useful in agriculture.

The plant cuticle, or skin, is needed to retain water and protect plants from external agents. A major component of the cuticle is the polymer cutin, but it has been unclear how this polymer is made. It was speculated that a family of enzymes, the GDSLs, might play a role in synthesizing the polymer, but the numerous and diverse functions of the GDSLs made identifying a specific enzyme challenging.

Jocelyn Rose and colleagues use a tomato mutant plant deficient in cutin production to track down the enigmatic enzyme, showing that it is indeed a GDSL. Loss of the enzyme leads to accumulation of the proposed substrate, and in vitro experiments show that the enzyme can make short chains of ester molecules in agreement with the expected function.