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 BBM1 genes, and in other
crop plants as well, Sundaresan said.