Formins are well-known regulators that participate in the organization of the actin cytoskeleton in organisms.The Arabidopsis thaliana L.genome encodes 21 formins,which can be divided into two distinct subfamilies.However,type II formins have to date been less well characterized.Here,we cloned a type II formin,AtFH16,and characterized its biochemical activities on actin and microtubule dynamics.The results show that the FH1FH2 structure of AtFH16 cannot nucleate actin polymerization effciently,but can bind and bundle microflaments.AtFH16 FH1FH2 is also able to bind and bundle microtubules,and preferentially binds microtubules over microflaments in vitro.In addition,AtFH16 FH1FH2 co-localizes with microtubules in onion epidermal cells,indicating a higher binding affnity of AtFH16 FH1FH2 for microtubules rather than microflaments in vivo.In conclusion,AtFH16 is able to interact with both microflaments and microtubules,suggesting that AtFH16 probably functions as a bifunctional protein,and may thus participate in plant cellular processes.
