Abstract
Auxin plays a key role in emergence of complexity in morphogenesis. Auxin induces interaction of the receptor TIR1 and AUX/IAA proteins, which causes poly-ubiquitination and subsequent degradation of the AUX/IAA proteins. Degradation of AUX/IAA proteins induces auxin responses. Five TIR1 homologues AFB1-5 are also implicated in auxin perception, and they may have different auxin-specificities. Also, there may be different interaction-preferences between these TIR1/AFBs and AUX/IAAs. These diversities may be responsible for complex auxin responses. Here we aimed to test interaction-specificities between every receptor and AUX/IAA using a heterologous yeast system, because yeasts expressing TIR1 have been reported to degrade IAA17 in an auxin-dependent manner. We here constructed yeast strains expressing a pair of a receptor and a luciferase-fused AUX/IAA, for all combinations, and measured luciferase activity after addition of different auxin molecular species. The results suggested that TIR1 and AFB2 have partially different target specificities.
