Construction of a male sterility system for hybrid rice production via nuclear male sterility gene

Traditionally, the production of hybrid maize seed involved the removal of male flowers to prevent self-fertilization of the female flowers. Rice produces bisexual flowers, so mechanical emasculation is not as amenable. Therefore, hybrid rice production requires that the female parent be genetically male sterile. There are several tactics to achieve this including conditional male sterility and cytoplasmic male sterility, but in every case the propagation of the male-sterile line is difficult. Chang et al used a nuclear-encoded male-sterility gene, OsNP1, to resolve this conflict. Into a osnp1-1 (male sterile) background, they introduced a transgene that 1) restores male fertility of the sporophyte, 2) makes pollen grains inviable, and 3) marks pollen carrying the transgene with red-fluorescent protein. Through self-pollination and seed sorting, this strategy produces both male-sterile plants for hybrid seed production and a fertile maintainer of male sterility. Proc. Natl. Acad. Sci. USA  10.1073/pnas.1613792113