Researchers at the University of California, Davis (UC Davis), have discovered a way to make rice plants replicate through seeds as clones. Though 400 species of wild plants produce viable seeds without fertilization, the same process has not evolved in most commercial crop species. The work led by postdoctoral researcher Imtiyaz Khanday and Venkatesan Sundaresan, professor of plant biology and plant sciences at UC Davis, is a major step forward.

The researchers discovered that the rice gene BBM1, belonging to a family of plant genes called "Baby Boom" (BBM), is expressed in sperm cells but not in eggs. After fertilization, BBM1 is expressed in the fertilized cell, but — at least initially — this expression comes from the male contribution to the genome. BBM1 switches on the ability of a fertilized egg to form an embryo.

Using gene editing, the researchers were able to prevent the plants from going through meiosis and form egg cells by mitosis, inheriting a full set of chromosomes from the mother. Then they caused these egg cells to express BBM1, which they would not normally do without fertilization. "So we have a diploid egg cell with the ability to make an embryo, and that grows into a clonal seed," Sundaresan said.

According to Sundaresan, the process has an efficiency of about 30 percent, but they hope it can be increased with more research. The approach should work in other cereal crops, which have equivalent BBM1genes, and in other crop plants as well, Sundaresan said.

For more details, read the news release from UC Davis.

Figure: Postdoc Imtiyaz Khanday and Professor Venkatesan Sundaresan with cloned rice plants in a UC Davis greenhouse, December 2018. Khanday, Sundaresan and colleagues have solved the problem of propagating cloned, hybrid plants from seed — a long-sought discovery with big implications for global agriculture. It could make it easier for the world's poorest farmers to grow high-yielding, disease-resistant or climate-tolerant crops and save their seeds for future use. (Karin Higgins/UC Davis)