Auxin-binding protein mutants in maize

Maize auxin-binding protein (ABP) is a putative auxin receptor. However, its function has not been clearly demonstrated. To study loss-of-function of maize Abp1 and Abp4, the two most highly expressed genes among the Abp multigene family in maize, we isolated insertion alleles of Robertson's Mutator. The loss-of-function of these mutants and the corresponding double mutants were confirmed by Northern and Western blot analyses. Despite the central importance of ABP supported in gain-of-function experiments, no obvious phenotypic aberration in these mutants was observed suggesting functional redundancy in this gene family in maize. In addition, compensatory mechanisms may be operating in maize because in abp4 loss-of-function mutants, ABP1 protein level was significantly elevated.