Regulation of Both Light- and Auxin - Mediated Development by the Arabidopsis lAA3 / SHY2 Gene

Light affects plant growth and development throughout the life cycle. However, light signals do not function autonomously but should be integrated with endogenous developmental factors such as the plant hormone auxin to specify correct developmental decisions. We have previously reported that theArabidopsis shy2-1D mutation alters various light responses, including highly photomorphogenic development in darkness. Here we show that the mutation also alters various auxin responses, including constitutive formation of lateral roots and reduced auxin sensitivity in inhibition of hypocotyl and root growth. The mutation is a gain of function mutation occuring in theIAA3 gene, one of theAux/IAA family genes encoding putative transcription factors of auxin-responsive genes. These results suggest that IAA3/SHY2 may play important roles in both light-and auxin-mediated development Considering that Aux/IAA proteins and auxin response transcription factors interact with one another, we propose that IAA3/SHY2 may integrate light signals into auxin-mediated developmental responses.