Auxin Amidohydrolases – From Structure to Function: Revisited

The control of plant growth and development is a well-coordinated process between exogenous and endogenous signals. Auxins are plant hormones belonging to the endogenous signals, which control a vast array of different processes. While auxins are growth promoting at low concentrations, higher levels are often inhibitory. Therefore, the tight control of auxin concentrations in a given plant tissue is essential. Among several processes that participate in auxin homeostasis, we focused herein on the process of reversible auxin conjugation that considers the synthesis of inactive auxin conjugates, which can be hydrolyzed back to the active form by so called auxin conjugate hydrolases. Although these proteins have been known for quite some time, their role in plants is still not clear, especially since novel hydrolases with different substrate specificities have been isolated. Thus, we have revisited the knowledge about auxin hydrolases, from their structure and biochemistry to the role in plant development and in dealing with unfavorable climate conditions.