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

Abstract

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.

MASSUGU2 Encodes Aux/IAA19, an Auxin-Regulated Protein That Functions Together with the Transcriptional Activator NPH4/ARF7 to Regulate Differential Growth Responses of Hypocotyl and Formation of Lateral Roots in Arabidopsis thaliana

“…Essentially the same results have been reported for SHY2/IAA3 (Oono et al, 2002;Tian et al, 2002) and AXR2/IAA7 (Nagpal et al, 2000).…”

A Gain‐of‐Function Mutation in IAA7/AXR2 Confers Late Flowering under Short‐day Light in ArabidopsisF

“…Dominant mutations in several AUX/IAA genes confer pleiotropic, auxin‐related phenotypes (Liscum and Reed 2002). Furthermore, mutations in domain II that stabilize AUX/IAA proteins result in the inhibition of auxin‐responsive reporter gene expression (Ouellet et al 2001; Oono et al 2002; Tatematsu et al 2004). The axr2‐1 mutation changes a single amino acid (Pro to Ser at codon 87) in conserved domain II of IAA7/AXR2; this stabilizes the AUX/IAA protein IAA7/AXR2, and thereby decreases auxin response (Nagpal et al 2000).…”

Regulation of Arabidopsis SHY2/IAA3 protein turnover

“…Among these, the short hypocotyl 2 (shy2-1), shy2-2, and shy2-3 mutations in SHY2/IAA3 caused short hypocotyls, slightly auxin resistant hypocotyl and root growth, reduced lateral root formation or outgrowth, slowed gravitropic response, and decreased auxin-regulated gene expression responses (Kim et al, 1996(Kim et al, , 1998Oono et al, 2002;Reed et al, 1998;Soh et al, 1999;Tian and Reed, 1999;Tian et al, 2002). shy2-2 plants have increased level of SHY2/IAA3 protein (Colo  n-Carmona et al, 2000), suggesting that these mutations stabilize SHY2/IAA3, thereby allowing it to inhibit auxin responses.…”