Differential expression of six glutamine synthetase genes in Zea mays

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.