Prenylation of the floral transcription factor APETALA1 modulates its function

The Arabidopsis MADS box transcription factor APETALA1 (AP1) was identified as a substrate for farnesyltransferase and shown to be farnesylated effici ently both in vitro and in vivo. AP1 regulates the transition from inflores cence shoot to floral meristems and the development of sepals and petals. A P1 fused to green fluorescent protein (GFP) retained transcription factor a ctivity and directed the expected terminal flower phenotype when ectopicall y expressed in transgenic Arabidopsis. However, ap1mS, a farnesyl cysteine- acceptor mutant of AP1, as well as the GFP-ap1mS fusion protein failed to d irect the development of compound terminal flowers but instead induced nove l phenotypes when ectopically expressed in Arabidopsis. Similarly, compound terminal flowers did not develop in era1-2 transformants that ectopically expressed AP1. Together, the results demonstrate that AP1 is a target of fa rnesyltransferase and suggest that farnesylation alters the function and pe rhaps specificity of the transcription factor.