title: A novel chimeric low-molecular-weight glutenin subunit gene from the wild relatives of wheat Aegilops kotschyi and Ae. juvenalis: evolution at the Glu-3 loci.
abstract: Four LMW-m and one novel chimeric (between LMW-i and LMW-m types) low-molecular-weight glutenin subunit (LMW-GS) genes from Aegilops neglecta (UUMM), Ae. kotschyi (UUSS), and Ae. juvenalis (DDMMUU) were isolated and characterized. Sequence structures showed that the 4 LMW-m-type genes, assigned to the M genome of Ae. neglecta, displayed a high homology with those from hexaploid common wheat. The novel chimeric gene, designed as AjkLMW-i, was isolated from both Ae. kotschyi and Ae. juvenalis and shown to be located on the U genome. Phylogentic analysis demonstrated that it had higher identity to the LMW-m-type than the LMW-i-type genes. A total of 20 single nucleotide polymorphisms (SNPs) were detected among the 4 LMW-m genes, with 13 of these being nonsynonymous SNPs that resulted in amino acid substitutions in the deduced mature proteins. Phylogenetic analysis demonstrated that it had higher identity to the LMW-m-type than the LMW-i-type genes. The divergence time estimation showed that the M and D genomes were closely related and diverged at 5.42 million years ago (MYA) while the differentiation between the U and A genomes was 6.82 MYA. We propose that, in addition to homologous recombination, an illegitimate recombination event on the U genome may have occurred 6.38 MYA and resulted in the generation of the chimeric gene AjkLMW-i, which may be an important genetic mechanism for the origin and evolution of LMW-GS Glu-3 alleles as well as other prolamin genes.
authors.affiliation: Key Laboratory of Genetics and Biotechnology, College of Life Science, Capital Normal University, Beijing, China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Li
authors.forename: Wujun
authors.initials: W
authors.lastname: Ma
authors.forename: Liyan
authors.initials: L
authors.lastname: Gao
authors.forename: Yanzhen
authors.initials: Y
authors.lastname: Zhang
authors.forename: Aili
authors.initials: A
authors.lastname: Wang
authors.forename: Kangmin
authors.initials: K
authors.lastname: Ji
authors.forename: Ke
authors.initials: K
authors.lastname: Wang
authors.forename: Rudi
authors.initials: R
authors.lastname: Appels
authors.forename: Yueming
authors.initials: Y
authors.lastname: Yan