Expression Pattern of Aux/IAA Genes in the iaa3/shy2‐1D Mutant of Arabidopsis thaliana (L.).

OONO, YUTAKA; OOURA, CHIHARU; UCHIMIYA, HIROFUMI

A semi‐dominant mutant suppressor of hy2 (shy2‐1D) of Arabidopsis thaliana, originally isolated as a photomorphogenesis mutant, shows altered auxin responses. Recent molecular cloning revealed that the SHY2 gene is identical to the IAA3 gene, a member of the primary auxin‐response genes designated the Aux/IAA gene family. Because Aux/IAA proteins are reported to interact with auxin response factors, we investigated the pattern of expression of early auxin genes in the iaa3/shy2‐1D mutant. RNA hybridization analysis showed that levels of mRNA accumulation of the early genes were reduced dramatically in the iaa3/shy2‐1D mutants, although auxin still enhanced gene expression in the iaa3/shy2‐1D mutant. Histochemical analysis using a fusion gene of the auxin responsive domain (AuxRD) and the GUS gene showed no IAA‐inducible GUS expression in the root elongation zone of the iaa3/shy2‐1D mutant. On the other hand, ectopic GUS expression occurred in the hypocotyl, cotyledon, petiole and root vascular tissues in the absence of auxin. These results suggest that IAA3/SHY2 functions both negatively and positively on early auxin gene expression.

ARABIDOPSIS thaliana; AUXIN; GENES; GENE expression; PLANT roots

Annals of Botany, 2002, Vol 89, Issue 1, p77

0305-7364

Academic Journal

10.1093/aob/mcf007