A gene that codes for (i.e., causes to be produced by an organism possessing that gene) the enzyme known as citrate synthase.
A bacterial gene that is utilized by certain bacteria (e.g., Pseudomonas) to code for (i.e., cause to be produced by bacterium possessing that gene) the enzyme known as citrate synthase. That enzyme is utilized to synthesize (i.e., create) citric acid. In 1996, Luis Herrera-Estrella discovered that inserting the CSb gene from Pseudomonas aeruginosa into certain plants caused those plants to produce up to ten times more citrate in their roots, and to release up to four times more citric acid from those roots into the surrounding soil (thus decreasing aluminum toxicity, which slows plant growth and decreases crop yields).