The discovery of Nongken 58S, a natural recessive photoperiod-sensitive male sterile line, served as a starting point for development of two-line hybrid rice in China. While original Nongken 58S in its japonica background is photoperiod-sensitive male sterile, after introgressing of the related locus into indica rice background the same trait become mainly temperature-sensitive male sterile. Although those photoperiod- and temperature-sensitive male sterile lines have been successfully used in two-line hybrid rice seed production, the genetic cause remained a mystery till the two recent publications, with one in Cell Research.