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Title: Transposon tagging of a male-sterility, female-sterility gene, St8, revealed that the meiotic MER3 DNA helicase activity is essential for fertility in soybean

Author
item BAUMBACH, JORDAN - University Of Wisconsin
item PUDAKE, RAMESH - University Of Wisconsin
item JOHNSON, CALLIE - University Of Wisconsin
item KLEINHANS, KAYLIN - University Of Wisconsin
item OLLHOFF, ALEX - University Of Wisconsin
item PALMER, REID - Iowa State University
item BHATTACHARYYA, MADAN - Iowa State University
item Sandhu, Devinder

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2016
Publication Date: 3/1/2016
Citation: Baumbach, J., Pudake, R.N., Johnson, C., Kleinhans, K., Ollhoff, A., Palmer, R.G., Bhattacharyya, M.K., Sandhu, D. 2016. Transposon tagging of a male-sterility, female-sterility gene, St8, revealed that the meiotic MER3 DNA helicase activity is essential for fertility in soybean. PLoS One. 11(3): e0150482. doi: 10.1371/journal.pone.0150482.

Interpretive Summary: Functional characterization of plant genes is a key for utilization of these genes for crop improvement. In this investigation we have used an active jumping gene called Tgm9 for characterization of a fertility gene in soybean. We studied a male-sterile, female-sterile mutant and showed that the loss of function in the mutant was due to the presence of Tgm9 in a gene involved in the development of reproductive cells. The disruption caused by the insertion of the jumping gene led to the loss of function of the fertility gene. Our study is the first to provide conclusive evidence that the jumping genes are active in soybean and also demonstrates that we can use them for functional characterization of soybean genes. Characterization of the gene involved in fertility is going to be a significant advance in understanding the reproductive biology of soybean and other plants. A better understanding of fertility in soybean may help soybean breeders in developing a commercially viable soybean hybrid for farmers.

Technical Abstract: The W4 locus in soybean encodes a dihydroflavonol-4-reductase (DFR2) that regulates pigmentation patterns in flowers and hypocotyl. The mutable w4-m allele that governs variegated flowers has arisen through insertion of a CACTA-type transposable element, Tgm9, in DFR2. In the w4-m line, reversion from variegated to purple flower indicates excision of Tgm9, and its insertion at a new locus. Previously, we have identified a male-sterile, female-sterile mutant among the selfed progenies of a revertant plant carrying only purple flowers. Co-segregation between Tgm9 and the sterility phenotype suggested that the mutant was generated by insertion of Tgm9 at the St8 locus. The transposon was localized to exon 10 of Glyma.16G072300 that shows high identity to the MER3 DNA helicase involved in crossing over. Molecular analysis of fertile branches from two independent revertant plants confirmed precise excision of Tgm9 from the st8 allele, which restored fertility. Phylogenetic analysis placed St8 in a clade with the Arabidopsis and rice MER3 and suggested that it is the only MER3-like gene in soybean. In soybean, the gene is expressed in flower-buds, trifoliate leaves and stem. This study demonstrated the use of Tgm9 system for gene identification and its applicability in forward and reverse genetics studies.