Abstract
Key message
The AGPase large subunit (shrunken-2) promoter was demonstrated to be active in the placentochalaza and endosperm of developing grain as well as the root tips in transgenic sorghum.
Abstract
The temporal and spatial expression patterns of the Sorghum bicolor Shrunken-2 (Sh2) promoter were evaluated using the green fluorescence protein reporter gene (gfp) in transgenic sorghum, within the context of upregulating starch biosynthesis in the developing grain. GFP fluorescence was analysed throughout development in various tissue types using confocal laser scanning microscopy techniques. Sh2 promoter activity was first detected in the placentochalaza region of the developing caryopsis and apoplasm adjacent to the nucellar epidermis at 7 days post anthesis (dpa) where fluorescence remained relatively constant until 17 dpa. Fluorescence in this region weakened by 20 dpa and disappeared by 25 dpa. Expression was also detected in the developing endosperm, but not until 12 dpa, continuing until 25 dpa. Whilst the endosperm expression was expected, the fluorescence detected in the placentochalaza was completely unexpected. Although transcript presence does not mean the resulting biochemistry is also present, these preliminary findings may suggest alternate spatial activity of ADP-glucose pyrophosphorylase prior to uptake by the developing grain. Sh2 promoter activity was also unexpectedly detected in the root tips at all developmental time points. Sh2 promoter activity was not detected in any reproductive floral tissue (both pre and post anthesis) or in pollen. Similarly, no expression was detected in leaf tissue at any stage.
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We are thankful to the ARC (Australian Research Council) and the GRDC (Grains Research and Development Corporation) for their financial support on the project UQ00076.
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Communicated by Zeng-Yu Wang.
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Supplementary Figure PCR detection of the nptII gene in putative transgenic lines. Lines from left to right: B no template control, U 1-5 samples of putative Ubi:gfp lines, L 2-log DNA ladder (NEW ENGLAND BIOLABS), S 1-10 samples of putative Sh2:gfp lines, C 1-2 non-transgenic Tx430 control (DOCX 626 kb)
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Lamont, K.C., Mudge, S.R., Liu, G. et al. Expression patterns of the native Shrunken-2 promoter in Sorghum bicolor visualised through use of the GFP reporter gene. Plant Cell Rep 36, 1689–1700 (2017). https://doi.org/10.1007/s00299-017-2182-4
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DOI: https://doi.org/10.1007/s00299-017-2182-4