title: Selection and molecular characterization of a lipoxygenase-free soybean mutant line induced by gamma irradiation.
abstract: A lipoxygenase-free soybean mutant line (H70) induced by gamma ray was selected and its detailed information about the lipoxygenase was analyzed by comparison of DNA sequence. Soybean seeds contain three lipoxygenase enzymes, which induce a beany or grassy flavor. The elimination of lipoxygenases can reduce the poor stability and off-flavors of soybean oil and protein products. In this study, we selected a soybean mutant (H70) in which the three lipoxygenases had been mutated using gamma rays. To obtain detailed information about the lipoxygenase, we investigated the sequences of the Lox1, Lox2 and Lox3 genes in H70 compared to the original cultivar, Hwanggum. Comparisons of the sequences of the Lox1 and Lox2 genes in H70 with those in a line with normal lipoxygenase (HG) showed that the mutations in these genes affected a highly conserved group of six histidine residues necessary for enzymatic activity. Lox1 in H70 contained a 74 bp deletion in exon 8, creating a stop codon that prematurely terminates translation. A single point mutation (T-A) in exon 8 of Lox2 changed histidine (H532, one of the iron-binding ligands essential for Lox2 activity) to glutamine. The mutation in the Lox3 gene in H70 was a single-point mutation in exon 6 (A-G), which changed the amino acid from histidine to arginine. This amino acid alteration in Lox3 was located in the N-terminal barrel, which might play a role in molecular recognition during catalysis and/or proteolysis. These results suggest that gene analysis based on DNA sequencing could be useful for elucidating the lipoxygenase content in soybean mutant lines. Additionally, the soybean mutant line selected in this study could be used to develop soybean cultivars with improved flavor.
authors.affiliation: Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, 1266 Sinjeong, Jeongeup, Jeonbuk, 580-185, Republic of Korea, lkj5214@kaeri.re.kr.
authors.forename: Kyung Jun
authors.initials: KJ
authors.lastname: Lee
authors.forename: Jung Eun
authors.initials: JE
authors.lastname: Hwang
authors.forename: Vijayanand
authors.initials: V
authors.lastname: Velusamy
authors.forename: Bo-Keun
authors.initials: BK
authors.lastname: Ha
authors.forename: Jin-Baek
authors.initials: JB
authors.lastname: Kim
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Kim
authors.forename: Joon-Woo
authors.initials: JW
authors.lastname: Ahn
authors.forename: Si-Yong
authors.initials: SY
authors.lastname: Kang
authors.forename: Dong Sub
authors.initials: DS
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D018744:DNA, Plant / Q000235:genetics; D005720:Gamma Rays; D017343:Genes, Plant; D008084:Lipoxygenase / Q000235:genetics*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D017354:Point Mutation; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D013025:Glycine max / Q000201:enzymology* / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D008084:Lipoxygenase