ABSTRACT
BACKGROUND: Homologous transformation sterility-1 (HTS-1) is a novel wheat mutant that exhibits pistillody, the transformation of stamens into pistils or pistil-like structures. More extreme phenotypes of this mutation can have six pistils or pistil-like structures without any stamens in a floret. Thus, HTS-1 is highly valuable for studies of wheat hybrid breeding and flower development. Previous studies have shown that two major genes (Pis1 and hts) control pistillody in HTS-1. The Pis1 gene controls the three-pistil trait in the three-pistil wheat mutant and has been mapped on chromosome 2D, but the hts gene has not been mapped or identified. To do so, we crossed HTS-1 with CM28TP (three-pistil mutant) and constructed a high-density linkage map with the F2 population (200 individuals). RESULTS: The map covered 2779.96 cM, and the genetic distance per chromosome ranged from 37.59 cM to 318.95 cM. The average distance between markers was 1.04 cM. We then mapped hts between GBS-SNP markers 4A_109 and 4A_119, separated by 2.0 cM and 5.2 Mb. To find the candidate genes, the hts region was enlarged to 7.2 Mb, encompassing 752 protein-coding genes. We identified TaWin1 as a possible candidate gene after comparing the 752 genes with 206 common differentially expressed genes between pistillody stamens (PS) versus normal stamens (S) and pistils (P) versus S. Real-time PCR indicated that TaWin1 was highly expressed in HTS-1 during the pistil-and-stamen-differentiating stage, at levels approximately 120 times greater than those in CM28TP. Further analysis indicated that TaWin1 was mainly expressed in HTS-1 PS, supporting its status as a candidate gene of hts. Thus, TaWin1 overexpression probably leads to the transformation of stamens into pistils in wheat. CONCLUSIONS: The results of this study provide a foundation for further research on stamen and pistil development, with implications for wheat-hybrid breeding programs.
