Expression of ArabidopsisSHORT INTERNODES/STYLISHFamily Genes in Auxin Biosynthesis Zones of Aerial Organs Is Dependent on a GCC Box-Like Regulatory Element    

Abstract

Auxin/indole-3-acetic acid (IAA) biosynthesis in Arabidopsis (Arabidopsis thaliana) plays a major role in growth responses to developmental and genetic signals as well as to environmental stimuli. Knowledge of its regulation, however, remains rudimentary, and few proteins acting as transcriptional modulators of auxin biosynthesis have been identified. We have previously shown that alteration in the expression level of the SHORT INTERNODES/STYLISH (SHI/STY) family member STY1 affects IAA biosynthesis rates and IAA levels and that STY1 acts as a transcriptional activator of genes encoding auxin biosynthesis enzymes. Here, we have analyzed the upstream regulation of SHI/STY family members to gain further insight into transcriptional regulation of auxin biosynthesis. We attempted to modulate the normal expression pattern of STY1 by mutating a putative regulatory element, a GCC box, located in the proximal promoter region and conserved in most SHI/STY genes in Arabidopsis. Mutations in the GCC box abolish expression in aerial organs of the adult plant. We also show that induction of the transcriptional activator DORNRÖ SCHEN-LIKE (DRNL) activates the transcription of STY1 and other SHI/STY family members and that this activation is dependent on a functional GCC box. Additionally, STY1 expression in the strong drnl-2 mutant or the drn drnl-1 puchi-1 triple mutant, carrying knockdown mutations in both DRNL and its close paralogue DRN as well as one of their closest homologs, PUCHI, was significantly reduced, suggesting that DRNL regulates STY1 during normal plant development and that several other genes might have redundant functions.

EARLY BUD-BREAK 1 (EBB1) is a regulator of release from seasonal dormancy in poplar trees

“…Interestingly and in support of the validity of our analysis, we found a significant enrichment among the 65 putative target genes of SHI RE-LATED SEQUENCE (SRS) genes (P < 0.001, Fisher's exact test). In Arabidopsis, SRS genes like SHORT INTERNODES (SHI) and STYLISH (STY) were demonstrated to be direct targets of DRN/ESR1 activation (32). Enrichment of various GO categories among the putative target genes suggests a broad regulatory context of EBB1 function.…”

“…In Arabidopsis, the EBB1 close orthologs (DRN/ESR1 and DRNL/ESR2) have been found to be positive regulators that bind to a GCC box sequence (32). Therefore, to identify putative direct targets of EBB1, we searched the promoter regions (−3,000 bp) of the 416 positively regulated genes for presence of a GCC box.…”

The Most Deeply Conserved Noncoding Sequences in Plants Serve Similar Functions to Those in Vertebrates Despite Large Differences in Evolutionary Rates

“…Four G-box motifs are conserved in eudicot genomes, and all four CNSs with phylogenetically conserved G-box motifs (CACGTG) are associated with genes shown to bind the bZIP transcription factor HY5 in an in vitro assay (Lee et al, 2007b). GCC-boxes are phylogenetically conserved in three of their five occurrences (Supplemental Figure 2B), and the GCC-box present in the promoter of SHI/STY RING-like zinc finger genes has been experimentally verified to be functional (Eklund et al, 2011). Whereas the overrepresented MSA box is only a 5-bp sequence (59AACGG), over half of its occurrences are phylogenetically conserved throughout eudicots (Supplemental Figure 2A).…”

Coordination of auxin-triggered leaf initiation by tomato LEAFLESS

“…We thus searched for additional elements that could regulate LFS expression. DRN can positively regulate a reporter comprising GCC-box elements (27), and DRNL positively regulates STY gene expression through GCC-box elements in their promoters (28). The upstream regions of both LFS and DRNL include conserved and extended GCC boxes (eGCC; 25 and 3.1 kbp upstream of LFS and 845 bp upstream of DRNL), suggesting that both genes may control their own expression.…”