Molecular characterization of lipoxygenase genes on chromosome 4BS in Chinese bread wheat (Triticum aestivum L.).

KEY MESSAGE: This study cloned two novel TaLox genes on chromosome of 4BS and developed a co-dominant marker, Lox-B23, in bread wheat that showed highly significant association with lipoxygenase activity. Lipoxygenase (Lox), a critical enzyme in the carotenoid biosynthetic pathway, significantly influences the color and processing quality of wheat-based products. Two novel Lox genes, designated TaLox-B2 and TaLox-B3, were cloned on chromosome 4BS of Chinese bread wheat. The deduced amino acid sequence showed that both TaLox-B2 and TaLox-B3 genes encoded an 861-aa protein and possessed a lipoxygenase superfamily domain at the 170-838 interval. Two different TaLox-B2 alleles, designated TaLox-B2a and TaLox-B2b, were subsequently discovered. A co-dominant marker, Lox-B23, was developed based on sequences of TaLox-B2a, TaLox-B2b, and TaLox-B3 genes to precisely distinguish these three alleles in Chinese bread cultivars. Among five allelic combinations of Lox genes at Lox-B1, Lox-B2, and Lox-B3 loci, wheat cultivars with TaLox-B1a/TaLox-B2a/TaLox-B3a combination exhibited the highest Lox activity, whereas those with TaLox-B1a/TaLox-B2b/TaLox-B3b combination significantly showed the lowest Lox activity. A RIL population was used to evaluate the influence of TaLox-B3a gene on Lox activity. Results showed that TaLox-B3a gene could significantly increase the Lox activity in bread wheat. Physical mapping indicated that both TaLox-B2 and TaLox-B3 genes were located on chromosome 4BS in bread wheat. This study provides useful information to further understand the molecular and genetic bases of Lox activity in bread wheat.