Journal Article

Decreased shoot stature and grain α-amylase activity following ectopic expression of a gibberellin 2-oxidase gene in transgenic wheat

Nigel E. J. Appleford, Mark D. Wilkinson, Qian Ma, Daniel J. Evans, Marlon C. Stone, Stephen P. Pearce, Stephen J. Powers, Stephen G. Thomas, Huw D. Jones, Andrew L. Phillips, Peter Hedden and John R. Lenton

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 58, issue 12, pages 3213-3226
Published in print September 2007 | ISSN: 0022-0957
Published online October 2007 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/erm166

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Ectopic expression of a gibberellin 2-oxidase gene (PcGA2ox1) decreased the content of bioactive gibberellins (GAs) in transgenic wheat, producing a range of dwarf plants with different degrees of severity. In at least one case, a single transformation event gave rise to T1 plants with different degrees of dwarfism, the phenotypes being stably inherited over at least four generations. The dwarf phenotype, which included dark-green leaves, increased tillering and, in severe cases, a prostrate growth habit, was replicated by the application of a GA biosynthesis inhibitor to the wild type. Ear rachis length, grain set, and grain size were also decreased in the wheat transformants, compared with an azygous (null) line. The extent of post-germination α-amylase production in grains reflected the severity of the shoot phenotype of the transformants and both developmental processes were restored to normal by the application of gibberellic acid (GA3). Expression of two GA biosynthesis genes (TaGA20ox1 and TaGA3ox2) was up-regulated, and that of two α-amylase gene families (α-Amy1 and α-Amy2) down regulated, in scutella of semi-dwarf lines, compared with controls. The marked decline in transcript abundance of both α-amylase gene families in aleurone was associated with a decreased content of bioactive GAs in grains of the semi-dwarf lines.

Keywords: α-Amylase; ear development; GA 2-oxidase; gene expression; gibberellin; grain size; paclobutrazol; shoot height; tillering; transgenic wheat

Journal Article.  10218 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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