Question

can lactose, casamino acid, and glucose stimulate GFP expression

Answer 1

GFP or green fluorescent protein is generally used as a tag or marker to help in visual identification of any gene expression. Depending on the kind of promoter under which the GFP is being expressed, different molecules can act as inducer or repressor for its expression.

In case if we use the lac operon, which operates to produce the enzyme beta-galactsidase which eventually helps in lactose metabolism, the presence of lactose acts as a simulator or inducer for the expression of GFP (GFP is inserted into the gene in place of the enzyme). However, if glucose (the preferred energy source) is present, it inhibits synthesis of CAP, a co-inducer for the lac operon and thus GFP expression does not occur.

Similarly, if we use PCK1 promoter whose main function is to produce the enzyme PCK1 involved in the procedure of synthesizing glucose from non-carbohydrate sources (process is called gluconeogenesis), then the cas-amino acids act as inducer for GFP expression as it is a non-carbohydrate source while glucose will be an inhibitor because the operon aims at synthesizing glucose.