Evolution of the primate glutamate taste sensor from a nucleotide sensor

Area of Science:

• Evolutionary biology
• Sensory neuroscience
• Molecular biology

Background:

• Taste perception, particularly umami, is crucial for food selection.
• The T1R1/T1R3 receptor complex detects amino acids, with high l-glutamate (l-Glu) sensitivity in humans, but not all vertebrates.

Purpose of the Study:

• To investigate the evolutionary origins of l-Glu sensitivity in primate T1R1/T1R3 receptors.
• To understand how sensory gene evolution facilitates adaptation to new food sources.

Main Methods:

• Receptor expression experiments to identify amino acid substitutions in T1R1/T1R3.
• Chemical analysis of l-Glu and 5'-ribonucleotides in primate diets (leaves and insects).

Main Results:

• l-Glu sensitivity evolved independently at least three times in primates that consume leaves.
• Insectivorous primates' T1R1/T1R3 receptors sense 5'-ribonucleotides, not l-Glu.
• Leaves contain abundant free amino acids like l-Glu, while insects are rich in 5'-ribonucleotides.

Conclusions:

• The shift in T1R1/T1R3 ligand preference from 5'-ribonucleotides to l-Glu likely promoted leaf consumption by overcoming aversive tastes.
• Repeated evolution of taste receptor sensitivity provides insight into primate foraging ecology and niche expansion.