Ever wonder how flowers get their Colors?
A section of the petal (B) shows the transition in color. Notice the change in cell volume (C) and pH (D) accompanying the color change. This is a caused by the induction of a gene, NHX1 that exchanges sodium or potassium ions for protons and regulates lumen pH. This gene was discovered serendipitously in my lab back in the '90's.
In humans, these same genes regulate pH inside synaptic vesicles and appear to be important for packaging neurotransmitters for release, and clearing them from the synaptic cleft. Mutations are linked to autism, addiction, ADHD and XLMR.