An Arginine-to-Histidine Mutation in Flavanone-3-Hydroxylase Results in Pink Strawberry Fruits.

Fruit color is a very important external commodity factor for consumers. Compared to the most typical red octoploid strawberry (Fragaria × ananassa), the pink strawberry often sells for a more expensive price and has a higher economic benefit due to its outstanding color. However, few studies have examined the molecular basis of pink colored strawberry fruit. Through an EMS mutagenesis of woodland strawberry (Fragaria vesca), we identified a mutant with pink fruits and green petioles. BSA-Seq analysis and gene function verification confirmed that the responsible mutation resides in a gene encoding flavanone-3-hydroxylase (F3H) in the anthocyanin synthesis pathway. This nonsynonymous mutation results in an arginine to histidine change at position 130 of F3H. Molecular docking experiments showed that the arginine to histidine mutation results in a reduction of intermolecular force-hydrogen bonding between the F3H protein and its substrates. Enzymatic experiments showed a greatly reduced ability of the mutated F3H protein to catalyze the conversion of the substrates, and hence a blockage of the anthocyanin synthesis pathway. The discovery of a key residue in the F3H gene controlling anthocyanin synthesis provides a clear target of modification for the molecular breeding of strawberry varieties with pink-colored fruits, which may be of great commercial value.