Baumbach Jordan, Pudake Ramesh N, Johnson Callie, Kleinhans Kaylin, Ollhoff Alexandrea, Palmer Reid G, Bhattacharyya Madan K, Sandhu Devinder
Department of Biology, University of Wisconsin-Stevens Point, Stevens Point, Wiconsin, 54481, United States of America.
Department of Agronomy, Iowa State University, Ames, Iowa, 50011, United States of America.
PLoS One. 2016 Mar 1;11(3):e0150482. doi: 10.1371/journal.pone.0150482. eCollection 2016.
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. In soybean, the gene is expressed in flower-buds, trifoliate leaves and stem. Phylogenetic analysis placed St8 in a clade with the Arabidopsis and rice MER3 suggesting that St8 is most likely the orthologous MER3 soybean gene. This study established the utility of Tgm9 in gene identification as well as in forward and reverse genetics studies.
大豆中的W4基因座编码一种二氢黄酮醇-4-还原酶（DFR2），该酶调节花和下胚轴的色素沉着模式。控制杂色花的可变w4-m等位基因是通过在DFR2中插入一个CACTA型转座元件Tgm9产生的。在w4-m品系中，从杂色花恢复为紫色花表明Tgm9被切除，并插入到一个新的基因座。此前，我们在一株仅开紫色花的回复植株的自交后代中鉴定出一个雄性不育、雌性不育的突变体。Tgm9与不育表型之间的共分离表明，该突变体是由Tgm9插入St8基因座产生的。转座子定位于Glyma.16G072300的第10外显子，该外显子与参与交叉的MER3 DNA解旋酶具有高度同源性。对两个独立回复植株的可育枝条进行分子分析，证实Tgm9已从st8等位基因中精确切除，从而恢复了育性。在大豆中，该基因在花芽、三出复叶和茎中表达。系统发育分析将St8置于与拟南芥和水稻MER3同一进化枝中，表明St8很可能是大豆中MER3的直系同源基因。本研究确立了Tgm9在基因鉴定以及正向和反向遗传学研究中的应用价值。
