Molecular Basis of Overdominance at a Flower Color Locus

• Published in: G3 : genes - genomes - genetics Vol. 7; no. 12; pp. 3947 - 3954
• Main Authors: LaFountain, Amy M, Chen, Wenjie, Sun, Wei, Chen, Shilin, Frank, Harry A, Ding, Baoqing, Yuan, Yao-Wu
• Format: Journal Article
• Language: English
• Published: England Genetics Society of America 01.12.2017; Oxford University Press
• Subjects: antagonistic pleiotropy; anthocyanins; Anthocyanins - biosynthesis; Anthocyanins - genetics; Color; FLAVONE SYNTHASE; Flavones - biosynthesis; Flavones - genetics; Flowers - genetics; Flowers - metabolism; Genes, Dominant - genetics; Genetic Pleiotropy; heterosis; Hybrid Vigor - genetics; Investigations; Mimulus; Mimulus - genetics; Mimulus - growth & development; Mixed Function Oxygenases - genetics; Pigmentation - genetics; Plants, Genetically Modified - genetics; FLAVONE SYNTHASE; heterosis; antagonistic pleiotropy; anthocyanins; Mimulus
• ISSN: 2160-1836; 2160-1836
• DOI: 10.1534/g3.117.300336

Single-gene overdominance is one of the major mechanisms proposed to explain heterosis ( , hybrid vigor), the phenomenon that hybrid offspring between two inbred lines or varieties show superior phenotypes to both parents. Although sporadic examples of single-gene overdominance have been reported over the decades, the molecular nature of this phenomenon remains poorly understood and it is unclear whether any generalizable principle underlies the various cases. Through bulk segregant analysis, chemical profiling, and transgenic experiments, we show that loss-of-function alleles of the ( ) gene cause overdominance in anthocyanin-based flower color intensity in the monkeyflower species FNS negatively affects flower color intensity by competing with the anthocyanin biosynthetic enzymes for the same substrates, yet positively affects flower color intensity by producing flavones, the colorless copigments required for anthocyanin stabilization, leading to enhanced pigmentation in the heterozyote ( ) relative to both homozygotes ( and ). We suggest that this type of antagonistic pleiotropy ( , alleles with opposing effects on different components of the phenotypic output) might be a general principle underlying single-gene overdominance.