A TOPLESS-related gene regulates both male and female sterility in wheat

Wheat yield mainly depends on thousand-grain weight, spike number per unit, and grain number per spike. Since fertility is directly related to seed setting rate and grain number, the discovery of novel genes and alleles affecting male or female sterility is essential for advancing the genetic understanding of wheat fertility. Here we identified a wheat mutant on anther-stigma development (asd), exhibiting both male and female sterility with thin shriveled non-dehiscent anthers that failed to release pollen, as well as visorless stigmas. Cytological examination of asd showed a lack of cutin polymer on anther surfaces and extensive microspore mother cell degeneration leading to pollen deficiency. Using MutMap⁺ and exome capture sequencing, we mapped one target gene on chromosome 2D, narrowing it a 1.62-Mb interval, and identifying TraesCS2D03G0987000 (TaTPR1), which encodes a conserved TOPLESS-related protein, as the candidate gene. TaTPR1 harbored a single base mutation (G > A) at the junction of the 6th intron and 7th exon, which disrupted splicing resulting in three transcripts. TaTPR1 expression levels were elevated in mutant anthers and ovaries, with subcellular localization confirming its presence in the nucleus and cytoplasm. Various allelic mutations within TaTPR1 exerted distinct impacts on pollen fertility and stigma development and led to reduced self-setting rates, which verified TaTPR1 to be the target gene. This study identified a crucial novel gene affecting both male and female sterility in wheat, which offers new insights into fertility mechanisms.