Transformation efficiencies and expression patterns of a series of truncated GS sub(1-2) promoter-GUS transgenes in maize

• Published in: Physiologia plantarum 2003-07, Vol.118 (3), p.346-351
• Main Authors: Muhitch, Michael J, Liang, Hua, Sollenberger, Kurtis G
• Format: Article
• Language: English
• Subjects: Zea mays
• ISSN: 0031-9317; 1399-3054
• DOI: 10.1034/j.1399-3054.2003.00122.x

One isoform of maize glutamine synthetase, encoded by GS sub(1-2), is localized exclusively in the maternal tissues of the developing kernel. Previously, we have demonstrated the ability of the proximal 664 base pair 5' upstream portion of GS sub(1-2) to drive maternal tissue-specific GUS expression in transgenic maize kernels (Muhitch et al. Plant Sci. 163: 865-872). In this report, a series of GS sub(1-2) promoter-GUS reporter transgenes, progressively truncated from the 5' end of the full length 664 base pair promoter, were evaluated for transformation efficiency and their ability to drive tissue-specific gene expression in transgenic maize. Analysis of transgene integration and expression suggests that GS sub(1-2)-GUS transgenes were incorporated efficiently into the maize genome, but were not expressed efficiently in maize cells. Truncation of the promoter from -664 to -394, -206 or -72, relative to the putative transcription start site, resulted in the loss of tissue specific expression within the kernels of transformed plants. Among the truncated series, moderate staining was exhibited by the -394 promoter-GUS gene transformants, stronger staining was found in -206 promoter-GUS gene transformants, but relatively weak and variable staining occurred in plants transformed with the -72-GUS gene. Likely explanations for these observations are considered.