Target genes and regulatory domains of the GAMYB transcriptional activator in cereal aleurone

Authors

  • Frank Gubler,

    1. 1 Co-operative Research Centre for Plant Science, PO Box 475, Canberra City, ACT, Australia, 2 Division of Plant Industry, CSIRO, GPO Box 1600, Canberra City, Australia, and 3 Department of Plant Physiology, Institute of Molecular Biology, University of Copenhagen, Oster Farimagsgade 2A, 1353-Copenhagen, Denmark
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  • 1 Dora Raventos,

    1. 1 Co-operative Research Centre for Plant Science, PO Box 475, Canberra City, ACT, Australia, 2 Division of Plant Industry, CSIRO, GPO Box 1600, Canberra City, Australia, and 3 Department of Plant Physiology, Institute of Molecular Biology, University of Copenhagen, Oster Farimagsgade 2A, 1353-Copenhagen, Denmark
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  • 3 Margaret Keys,

    1. 1 Co-operative Research Centre for Plant Science, PO Box 475, Canberra City, ACT, Australia, 2 Division of Plant Industry, CSIRO, GPO Box 1600, Canberra City, Australia, and 3 Department of Plant Physiology, Institute of Molecular Biology, University of Copenhagen, Oster Farimagsgade 2A, 1353-Copenhagen, Denmark
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  • 2 Robyn Watts,

    1. 1 Co-operative Research Centre for Plant Science, PO Box 475, Canberra City, ACT, Australia, 2 Division of Plant Industry, CSIRO, GPO Box 1600, Canberra City, Australia, and 3 Department of Plant Physiology, Institute of Molecular Biology, University of Copenhagen, Oster Farimagsgade 2A, 1353-Copenhagen, Denmark
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  • 1 John Mundy,

    1. 1 Co-operative Research Centre for Plant Science, PO Box 475, Canberra City, ACT, Australia, 2 Division of Plant Industry, CSIRO, GPO Box 1600, Canberra City, Australia, and 3 Department of Plant Physiology, Institute of Molecular Biology, University of Copenhagen, Oster Farimagsgade 2A, 1353-Copenhagen, Denmark
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  • and 3 John V. Jacobsen 2

    1. 1 Co-operative Research Centre for Plant Science, PO Box 475, Canberra City, ACT, Australia, 2 Division of Plant Industry, CSIRO, GPO Box 1600, Canberra City, Australia, and 3 Department of Plant Physiology, Institute of Molecular Biology, University of Copenhagen, Oster Farimagsgade 2A, 1353-Copenhagen, Denmark
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*For correspondence: Division of Plant Industry CSIRO, GPO Box 1600, Canberra City 2601, Australia (fax +61 02 6246 5000;
e-mail f.gubler@pi.csiro.au).

Summary

GAMYB is an MYB transcription factor which is expressed in cereal aleurone cells in response to gibberellin (GA). HvGAMYB binds to the TAACAAA box of a high-pI α-amylase gene promoter and transcriptionally activates its expression. In this study, we examined the role of HvGAMYB in activating expression of other GA-regulated genes encoding hydrolytic enzymes. In transient expression experiments, HvGAMYB transactivated expression of reporter genes fused to a low-pI α-amylase gene promoter, an EII(1–3,1–4)-β-glucanase gene promoter and a cathepsin B-like protease promoter. HvGAMYB DNA binding specificity was determined using a PCR-based random site selection using HvGAMYB fusion protein isolated from E. coli . The deduced consensus closely resembled gibberellin response elements in α-amylase promoters. Functional analysis of HvGAMYB by transient expression of C terminal HvGAMYB deletions in barley aleurone cells identified two transcriptional activation domains (TADs) which function in transcriptional regulation of both high- and low-pI α-amylase promoters. The same TADs were identified using a heterologous yeast expression system. Together, these results indicate that HvGAMYB has two TADs. These domains are C-terminal to its DNA-binding domain.

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