You are trying to identify DNA regulatory sequences that control the expression

Question

You are trying to identify DNA regulatory sequences that control the expression of a gene encoding a SAUR protein. The SAUR gene is expressed at high levels in auxin treated seedlings but at very low levels in untreated seedlings. You make the series of genes described below which each contain different lengths of the 5' gene flanking region. You transfer each gene into transgenic plants and measure its expression in auxin-treated and untreated seedlings. The following results are obtained. You also fuse the following fragments to the minimal 35S promoter fused with the GUS gene. After transferring the genes into transgenic plants, you obtain the following results. a) Which part(s) or basepair regions of the flanking region is sensitive to auxin? Explain your reasoning. b) Which part(s) or basepair regions of the flanking region is necessary for gene activation? Explain your reasoning.

Explanation / Answer

A region of 5’ flanking region from -400 to -1bp and -200 to -1bp region is sensitive to auxin because the expression of the mutated gene is not showing any expression in the presence of Auxins. The SAUR gene is expressed at high level in auxin treated seedlings but showing low levels in Auxin untreated seedlings. A region of 5’ flanking region fused with minimal promoter from -200 to -1bp and -400 to -200 bp region is is necessary for gene activation because GUS activity is showing positive expression in the absence of Auxin, which was earlier showing negative expression in the absence of Auxin so after fusing promoter with the GUS gene it will positively regulating its expression.

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