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GrainGenes Reference Report: PLC-14-1963

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Reference	PLC-14-1963
Title	Three novel MYB proteins with one DNA binding repeat mediate sugar and hormone regulation of alpha-amylase gene expression
Journal	Plant Cell
Year	2002
Volume	14
Pages	1963-1980
Author	Lu CA Ho TD Ho SL Yu SM
Abstract	Summary: The expression of alpha-amylase genes in cereals is induced by both gibberellin (GA) and sugar starvation. All alpha-amylase genes isolated from cereals contain a TATCCA element or its variants at positions approximately 90 to 150 bp upstream of the transcription start sites. The TATCCA element was shown previously to be an important component of the GA response complex and the sugar response complex of alpha-amylase gene promoters. In the present study, three cDNA clones encoding novel MYB proteins with single DNA binding domains were isolated from a rice suspension cell cDNA library and designated OsMYBS1, OsMYBS2, and OsMYBS3. Gel mobility shift experiments with OsMYBSs showed that they bind specifically to the TATCCA element in vitro. Yeast one-hybrid experiments demonstrated that OsMYBS1 and OsMYBS2 bind to the TATCCA element and transactivate a promoter containing the TATCCA element in vivo. Transient expression assays with barley half-seeds showed that OsMYBS1 and OsMYBS2 transactivate a promoter containing the TATCCA element when sugar is provided, whereas OsMYBS3 represses transcription of the same promoter under sugar starvation. Transient expression assays also showed that these three OsMYBSs cooperate with a GA-regulated transcription factor, HvMYBGa, in the transactivation of a low-pl barley alpha-amylase gene promoter in the absence of GA. Two-hybrid experiments with barley half-seeds showed that OsMYBS1 is able to form a homodimer. The present study demonstrates that differential DNA binding affinity, promoter transactivation ability, dimerization, and interactions with other protein factors determine the biological function of OsMYBSs. This study also suggests that common transcription factors are involved in the sugar and hormonal regulation of alpha-amylase gene expression in cereals
Keyword	[ Hide all but 1 of 45 ] absence aleurone cells alpha-amylase alpha-amylase gene amino acid sequence assay barley barley alpha-amylase binding domain binding domains cdna cdna clone cdna library cell complementary dna complexes dna dna binding element gel gene genetic regulation gibberellin glucose hormonal regulation hormone in vitro in vivo mediate mobility nucleotide sequence one-hybrid oryza sativa position promoter regulation repeat rice starvation sugar sugar starvation transcription transient transient expression yeast

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