|HE, TINGTING - Nanjing Agricultural University
|DING, XIANLONG - Nanjing Agricultural University
|ZHANG, HAO - Nanjing Agricultural University
|CHEN, LINFENG - Nanjing Agricultural University
|WANG, TANLIU - Nanjing Agricultural University
|YANG, LONGSHU - Nanjing Agricultural University
|NIE, ZHIXING - Nanjing Agricultural University
|GAI, JUNYI - Nanjing Agricultural University
|YANG, SHOUPING - Nanjing Agricultural University
Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2020
Publication Date: 1/6/2021
Citation: He, T., Ding, X., Zhang, H., Chen, L., Wang, T., Yang, L., Nie, Z., Song, Q., Gai, J., Yang, S. 2021. Comparative analysis of mitochondrial genomes of soybean cytoplasmic male sterile lines and their maintainer lines. Frontiers in Plant Science. 21(1):43-57. https://doi.org/10.1007/s10142-020-00760-x.
Interpretive Summary: The mitochondrion is a cellular organelle that powers the cell. The mitochondriaon has a small, circular DNA genome that is independent of the chromosomal DNA genome found in the nucleus. DNA sequence mutations in mitochondrial genomes can cause functional disorder such as cytoplasmic male sterility (CMS) in plants, a phenomenon whereby pollen does not fully form and becomes useless for pollination. CMS is exploited by breeders to produce hybrids in some major crops such as rice, maize, and rapeseed. CMS lines account for more than half of the total production for each crop. Although mitochondrial DNAsequences of CMS lines have been reported in many crops, only one mitochondrial genome of a non-CMS cultivar has been reported for soybean. Furthermore, the genes controlling CMS in soybean are unknown. In this study, scientists from China and USDA-ARS sequenced mitochondrial genomes of two CMS soybean lines and three maintainer lines and compared the sequence differences between them. Because maintainer lines have the same nuclear background but different mitochondria compared to their corresponding CMS lines, the scientists were able to compare the mitochondrial DNA sequences and identify two genes related to the CMS. The two candidate genes (orf179 and orf262 ) have the sequence characteristics of CMS genes in other crops. The genes were found to be expressed in the CMS lines but not in the maintainer lines in a validation test. This information will help scientists and breeders at universities, government agencies, private institues, and companies understand the mechanisms regulating CMS and should help them develop better varieties of hybrid soybean with improved agricultural traits.
Technical Abstract: Cytoplasmic male sterility (CMS) is widely used to produce hybrids. Although mitochondrial sequence of CMS lines has been reported in many crops, only one mitochondrial genome of a non-CMS cultivar has been sequenced in soybean. The difference between the mitochondrial genomic sequence of the CMS lines and their maintainer lines is unknown. A comparative analysis of the mitochondrial genome (mtDNAs) sequence from five soybean CMS lines and their maintainer lines showed that mitochondria gene sequences were highly conserved between CMS lines and maintainer lines. The mitochondrial genomes of CMS and maintainer lines not only had conserved sequence but also unique sequence. Soybean mitochondrial genomes contained more than 60% sequences originated from nucleus and plastid. Most of these sequences were homologous to the sequence in pericentromeric regions of chromosomes in nucleus. The pericentromeric regions were hot spots for large fragment transfer between the mitochondrion and nucleus. Repeat sequence, unique sequence, exogenous sequence (mitochondrial sequence homologous to chloroplast and nuclear genome) and partial genes were involved in the recombination of mitochondrial genome, which constituted a complex recombination network. The orf179 and orf262 were candidate genes controlling CMS, they had the sequence characteristics of reported CMS genes in other crops and could be transcribed in the CMS lines but not the maintainer lines. This is the first report to reveal mitochondrial genomes of soybean CMS lines and make comparative analysis of complete mitochondrial genomes of CMS lines and their maintainer lines for the identification of CMS genes. The information obtained in this study will help scientists to understand the characteristics of soybean mitochondrial genome and the mechanism underlying CMS and facilitate the development of hybrid seeds in soybean.