The SUR2 gene of Arabidopsis thaliana encodes the cytochrome P450CYP83B1, a modulator of auxin homeostasis

Genetic screens have been performed to identify mutants with altered auxin homeostasis in Arabidopsis. A tagged allele of the auxin-overproducing muta nt sur2 was identified within a transposon mutagenized population. The SUR2 gene was cloned and shown to encode the CYP83B1 protein, which belongs to the targe family of the P450-dependent monooxygenases. SUR2 expression is u p-regulated in sur1 mutants and induced by exogenous auxin in the wild type . Analysis of indole3-acetic acid (IAA) synthesis and metabolism in sur2 pl ants indicates that the mutation causes a conditional increase in the pool size of IAA through up-regulation of IAA synthesis.