cis Elements and trans-Acting Factors Affecting Regulation of a Nonphotosynthetic Light-Regulated Gene for Chloroplast Glutamine Synthetase

Abstract

The glutamine synthetase (GS) gene family in pea (Pisum safivum) consists of four nuclear genes encoding distinct isoenzymes. Molecular studies have shown that the GS2 gene encoding chloroplastlocalized CS is expressed in specific cell types and is regulated by diverse factors such as light and photorespiration. Here, we present the nucleotide sequence of the pea GS2 gene promoter. To identify the elements involved in regulation of GS2 expression, GS2 promoter-deletion analyses were performed using GS2-GUS fusions in tobacco (Nicotiana tabacum). This analysis revealed that the CS2 transit peptide is not required for mesophyll cell-specific expression of P-glucuronidase (CUS). CUS activity was induced 2-to 4-fold in light-grown versus etiolated T, seedlings. However, high levels of CUS activity were observed in etiolated seedlings. This observation demonstrated that regulation of expression of GS2, a nonphotosynthetic light-regulated gene, involves additional factors. A 323-bp CSZ promoter sequence i s sufficient to confer light regulation to the CUS reporter gene in leaves of mature transgenic tobacco. Lightregulated expression of this pea gene promoter is observed in both tobacco and Arabidopsis, suggesting that the regulatory elements are conserved. Cel-shift analysis detected DNA-protein complexes formed with potential transcription elements within this short, light-responsive CS2 promoter fragment.

Histone Deacetylase AtHDA7 Is Required for Female Gametophyte and Embryo Development in Arabidopsis

“…The motif at position 2245 is similar to the binding site of SBF1, a transcriptional repressor (Lawton et al, 1991). On the other hand, motifs including ZC2 recognized by chromatin remodelers with zinc-finger domains (Ponte et al, 1994), telobox recognized by Athb homeodomain proteins (Sessa et al, 1993), W-box recognized by WRKY transcription factors (Eulgem et al, 2000), BOX1* (Tjaden et al, 1995), and GCCAAG motif (Leah et al, 1994) are reported to be involved in transcriptional activation. The predicted motif composition of the AtHDA7 promoter suggests that its transcription is regulated in a complex way.…”

Light Regulation of Nitrate uptake, Assimilation and Metabolism

“…Light responsive GS2 promoters were demonstrated for Phaseolus vulgaris (Cock et al 1992) and pea (Tjaden et al 1995). The GS2 pea promoter contains an AT-rich 33 bp region at 807 bp upstream of the transcription start site, and when this AT-rich region was deleted, expression was reduced 10-fold (Tjaden and Coruzzi 1994).…”

Use of Arabidopsis mutants and genes to study amide amino acid biosynthesis.

“…However, a direct linkage between gene expression and the light-signal transduction pathway is still absent. Some nitrogen assimilation gene promoters, including those of pea GS2 and AS, are known to possess light-responsive elements (Tjaden et al, 1995;F.-Y. Tsai (B) A portion of Figure 2A is enlarged to show that the changes in GLN2 and ASN1 mRNA levels under light and dark conditions are paralleled by changes in glutamine and asparagine levels (also see Table 2 and Figure 1).…”