Differential expression of six glutamine synthetase genes in Zea mays

Abstract

The maize genome has been shown to contain six glutamine synthetase (GS) genes with at least four different expression patterns. Noncoding 3' gene-specific probes were constructed from all six GS cDNA clones and used to examine transcript levels in selected organs by RNA gel blot hybridization experiments. The transcript of the single putative chloroplastic GS2 gene was found to accumulate primarily in green tissues, whereas the transcripts of the five putative GS1 genes were shown to accumulate preferentially in roots. The specific patterns of transcript accumulation were quite distinct for the five GS1 genes, with the exception of two closely related genes.

Two Cytosolic Glutamine Synthetase Isoforms of Maize Are Specifically Involved in the Control of Grain Production

“…However, this distinction is not as simple as was first thought because although only one gene has been shown to encode the plastidic form, a small family of up to five genes is now known to encode the cytosolic form (Cren and Hirel, 1999). Initial experiments indicated that the five cytosolic GS genes were differentially expressed in the roots, stems, and leaves of maize (Sakakibara et al, 1992(Sakakibara et al, , 1996Li et al, 1993). In a more recent study of maize leaves performed by Hirel et al (2005b), it was shown that two of the five genes encoding GS1 (Gln1-3 and Gln1-4) were highly expressed regardless of the leaf age and the level of N fertilization, although there was an increase in Gln1-4 transcripts in the older leaves.…”

“…GS1-2, which is an important GS isoenzyme of the developing kernel, is abundant in the pedicel and pericarp but has also been shown to be present in immature tassels, dehiscing anthers, kernel glumes, ear husks, cobs, and stalks of maize plants (Muhitch et al, 2002;Muhitch, 2003). Compared with the four other genes encoding GS1, Gln1-5 is expressed at a very low level in leaves, roots, and stems (Sakakibara et al, 1992;Li et al, 1993). The plastidic GS (GS2) encoded by Gln2 was only expressed in the early stages of plant development, presumably to reassimilate ammonium released during photorespiration, which is at a much lower rate in a C 4 plant compared with a C 3 plant (Ueno et al, 2005).…”

“…For clarity and as the Gln1-3 and Gln1-4 genes show high sequence similarity, they are shown as a single structure. The Gln1-3 and Gln1-4 gene structure and exon sizes were determined by sequencing genomic DNA PCR products using primers designed from the corresponding cDNA sequences (Li et al, 1993): the Mu insertion sequences and the rice genomic clone AC105364. The rice and Gln1-3 and Gln1-4 genes consist of 10 exons (black arrows), ranging in size from 40 to 252 bp, and nine introns (black lines).…”

Molecular Identification and Characterization of Cytosolic Isoforms of Glutamine Synthetase in Maize Roots

“…These clones were originally designated pGS107, pGS112, pGS117, and pGS122 (9) but they were recently renamed pGS1a, 2 pGS1b, pGS1c, and pGS1d, respectively. A fifth cDNA for a cytosolic GS, ZMGS12 (pGS1e), has also been reported (10). Studies with gene-specific probes have revealed clear differences among the patterns of expression of the various genes at the mRNA level (9 -11).…”

Immunolocalization of a Unique Form of Maize Kernel Glutamine Synthetase Using a Monoclonal Antibody

“…moto et al, 1989;Sakakibara et al, 1992;Li et al, 1993). These GS isozymes are active in root and leaf primary ammonia assimilation, in leaf photorespiration, and in storage organ, root nodule, and senscent tissue Gln synthesis for intercellular transport (Kawakami and Watanabe, 1988;Coruzzi, 1991).…”