A candidate male-fertility female-fertility gene tagged by the soybean endogenous transposon, Tgm9

Abstract

In soybean, the W4 gene encoding dihydroflavonol-4-reductase controls anthocyanin pigment biosynthesis in flowers. The mutant allele, w4-m, is characterized by variegated flowers and was evolved from the insertion of an endogenous transposable element, Tgm9, in intron II of the W4 gene. In the w4-m mutant line, reversion of the unstable allele from variegated to normal purple flower in revertants would indicate Tgm9's excision accompanied by its insertion into a second locus. We identified a male-sterile, female-sterile mutant from such germinal revertant bearing purple flowers. The objectives of our investigation were to map the sterility locus, identify candidate genes for the male-fertile, female-fertile phenotype, and then determine if sterility is associated with the insertion of Tgm9 in the sterility locus. We used bulked segregant analysis to map the locus to molecular linkage group J (chromosome 16). Fine mapping enabled us to flank the locus to a 62-kb region that contains only five predicted genes. One of the genes in that region, Glyma16g07850.1, codes for a helicase. A rice homolog of this gene has been shown to control crossing over and fertility phenotype. Thus, Glyma16g07850.1 is most likely the gene regulating the male and female fertility phenotype in soybean. DNA blot analysis of the segregating individuals for Tgm9 showed perfect association between sterility and the presence of the transposon. Most likely, the sterility mutation was caused by the insertion of Tgm9. The transposable element should facilitate identification of the male- and female-fertility gene. Characterization of the fertility gene will provide vital molecular insight on the reproductive biology of soybean and other plants.

Soybean (Glycine max) Mutant and Germplasm Resources: Current Status and Future Prospects

“…Later, Raval et al. () utilized the Tgm9 transposon tagging system to identify an insertion within a DNA/RNA helicase/DEAD‐box protein gene that caused a male‐sterile, female‐sterile mutant. Recently, it has been demonstrated that excision of the element from the gene resulted in restoration of the male and female fertility wild‐type phenotype (M.K.…”

“…This screen yielded 36 independent male-sterile, femalefertile (MSFS) mutants and 24 independent root necrotic mutants, demonstrating the ability of this transposon to mutate other genes. Later, Raval et al (2013) utilized the Tgm9 transposon tagging system to identify an insertion within a DNA/RNA helicase/DEADbox protein gene that caused a male-sterile, female-sterile mutant. Recently, it has been demonstrated that excision of the element from the gene resulted in restoration of the male and female fertility wild-type phenotype (M.K.…”

Molecular mapping of five soybean genes involved in male-sterility, female-sterility

“…This sterility gene was inherited as a single recessive nuclear gene and was nonallelic to the known male-sterile, female-sterile mutants st2, st4, st5, st6, and st7 (Palmer and Horner 2000). The st8 gene was mapped to a 62-kb region on molecular linkage group (MLG) J; the mutation was caused by the insertion of an active soybean transposable element, Tgm9 (Kato and Palmer 2003;Raval et al 2013). …”

Microscopic Characterization of a Transposon-Induced Male-Sterile, Female-Sterile Mutant in Glycine max L.

“…A male-sterile, female-sterile (MSFS) mutant from a germinal revertant of the w4-m line bearing purple flowers was found at Iowa State University (Raval et al 2013). The locus was mapped to molecular linkage group J (chromosome 16) through bulked segregant analysis.…”

“…A 62-kb region was found, and fine mapping indicated that the region contained only five genes. One of the genes in that region, identified as Glyma.16G072300, encodes a helicase gene (Raval et al 2013). A rice homolog of this helicase gene has been shown to control crossing over and a sterility phenotype (Wang et al 2009).…”