A Small acidic protein 1 (SMAP1) mediates responses of the arabidopsis root to the synthetic auxin 2,4-dichlorophenoxyacetic acid

Rahman, A.*; Nakasone, Akari*; Chhun, T.*; Oura, Chiharu*; Biswas, K. K.*; Uchimiya, Hirofumi*; Tsurumi, Seiji*; Baskin, T. I.*; Tanaka, Atsushi; Ono, Yutaka

2,4-D, a chemical analogue of IAA, is widely used as a growth regulator and exogenous source of auxin. It is believed that they share a common response pathway. Here, we show that a mutant, () is resistant to 2,4-D, yet nevertheless responds like the wild type to IAA. That the mutation alters 2,4-D responsiveness specifically was confirmed by analysis of GUS expression in the and backgrounds, as well as by real-time PCR quantification of expression. Complementation and RNAi experiments identified a gene that confers 2,4-D responsiveness. The gene encodes a with unknown function and present in plants, animals, and invertebrates. These results suggest that SMAP1 is a regulatory component that mediates responses to 2,4-D and that responsiveness to 2,4-D and IAA are partially distinct.