SMAP1, a novel gene encoding small acidic protein revealed by mutant screening with antiauxin is involved in 2,4-D sensitivity but not IAA sensitivity in Arabidopsis roots

Abstract

We previously reported a novel Arabidopsis auxin-related mutant, aar1 (antiauxin resistant 1) that shows specific resistance to 2,4-D, yet nevertheless shows a wild type response to IAA and NAA in root elongation assay. The aar1 mutant was initially identified during a process of screening mutants in Arabidopsis thaliana against an antiauxin, p-chlorophenoxyisobutyric acid (PCIB). 2,4-D uptake and metabolism experiments did not show any difference between WT and the aar1-1 plants, implying the mutation alters the pathway for 2,4-D response. Molecular analyses revealed that a lack of a novel gene encodes small acidic protein 1 (SMAP1) confers the most of the the aar1 phenotype. The results suggest that 2,4-D/IAA response pathway in planta is at least in part different.