What role does arabinose play in the expression of the GFP gene?

Arabinose serves as an inducer for the expression of the Green Fluorescent Protein (GFP) gene in a system utilizing the pBAD promoter. When arabinose is added to the growth medium, it interacts with the regulatory proteins that are responsible for controlling the pBAD promoter. This interaction allows for the transcription of the GFP gene to initiate, leading to the production of GFP in the cells. The process is dependent on arabinose because, in the absence of arabinose, the promoter remains inactive, and GFP is not expressed.

In this context, the other options do not accurately reflect the role of arabinose. It is not a preservative, nor does it inhibit or alter the pH of the medium in a way relevant to GFP expression. Instead, its primary function is to stimulate the transcription of the GFP gene, thereby allowing for the desired protein production.