Abstract
The auxin primary-response proteins, Aux/IAA, usually have four conserved domains. However, Domains I and II are conserved imperfectly in the IAA20 subfamily proteins composed of IAA20, 30 and 31. Especially IAA20 and IAA30 lack Domain II, which has been thought essential for function of Aux/IAA proteins. In this study, we have examined phenotype of transgenic lines overexpressing IAA30 (IAA30 OX) and IAA31 (IAA31 OX) by the use of 35S promoter to understand function of the IAA20 subfamily. Both lines were defective in multiple auxin-related properties, such as gravitropism of hypocotyls and roots and lateral root formation. But only IAA31 OX displayed weaker apical dominance and late flowering. These results suggest that atypical Aux/IAA proteins also play a similar role in auxin signaling to the other Aux/IAAs, and have redundant and unique characteristics in the IAA20 subfamily.
