Mitotic Illegitimate Recombination Is a Mechanism for Novel Changes in High-Molecular-Weight Glutenin Subunits in Wheat-Rye Hybrids
Counts：DateTime：2014-12-28 19:11:07 Source: Wheat Research Institute
Click here to read full text
Zhongwei Yuan1, Dengcai Liu1,2*, Lianquan Zhang1, Li Zhang1, Wenjie
Chen1, Zehong Yan1, Youliang Zheng1, Huaigang Zhang2, Yang Yen3*
1 Triticeae Research Institute, Sichuan Agricultural University at
Chengdu, Wenjiang, Sichuan, People’s Republic of China, 2 Key Laboratory
of Adaptation and Evolution of
Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy
of Sciences, Xining, People’s Republic of China, 3 Department of Biology
and Microbiology, South
Dakota State University, Brookings, South Dakota, United States of America
Abstract:
Wide hybrids can have novel traits or
changed expression of a quantitative trait that their parents do not
have. These phenomena have long been noticed, yet the mechanisms are
poorly understood. High-molecular-weight glutenin subunits (HMW-GS) are
seed storage proteins encoded by Glu-1 genes that only express in
endosperm in wheat and its related species. Novel HMW-GS compositions
have been observed in their hybrids. This research elucidated the
molecular mechanisms by investigating the causative factors of novel
HMW-GS changes in wheat-rye hybrids. HMW-GS compositions in the
endosperm and their coding sequences in the leaves of F1 and F2 hybrids between wheat landrace Shinchunaga and rye landrace Qinling
were investigated. Missing and/or additional novel HMW-GSs were observed
in the endosperm of 0.5% of the 2078 F1 and 22% of 36 F2 hybrid seeds. The wildtype Glu-1Ax null allele was found to have 42 types of short repeat sequences of
3-60 bp long that appeared 2 to 100 times. It also has an in-frame stop
codon in the central repetitive region. Analyzing cloned allele
sequences of HMW-GS coding gene Glu-1 revealed that deletions involving the in-frame stop codon had happened, resulting in novel ~1.8-kb Glu-1Ax alleles in some F1 and F2 plants. The cloned mutant Glu-1Ax alleles were expressed in Escherichia coli,
and the HMW-GSs produced matched the novel HMW-GSs found in the
hybrids. The differential changes between the endosperm and the plant of
the same hybrids and the data of E. coli expression of the
cloned deletion alleles both suggested that mitotic illegitimate
recombination between two copies of a short repeat sequence had resulted
in the deletions and thus the changed HMW-GS compositions. Our
experiments have provided the first direct evidence to show that mitotic
illegitimate recombination is a mechanism that produces novel
phenotypes in wide hybrids.
Location：