Dead end for auxin conjugates in Physcomitrella?

For proper development of plants auxin levels need to be tightly controlled. For this, several routes have evolved and it is plausible that different organisms use these differently. To determine whether members of the family of GH3 proteins, which partially act as auxin conjugate synthetases in Arabidopsis thaliana, have similar roles in the moss Physcomitrella patens, we have investigated the in vitro activity of the two GH3 members in moss. We showed that both proteins can form amino acid conjugates with indole-3-acetic acid (IAA) but also with jasmonic acid (JA). Confirming these findings, single and double knockout-mutants showed lower levels of IAA conjugates than wild type. We discuss the results in light of the possible functions of IAA conjugate formation in lower land plants.