Around 30% more grain. This is the result announced in PNAS by Chinese researchers that have made the most of CRISPR’s multiplexability in rice. By simultaneously targeting multiple genes, the editing technique is a boon for scientists struggling with plants’ genetic redundancies.
Miao et al. edited thirteen genes associated with abscisic acid, a phytohormone which helps plants to resist adverse conditions by closing stomata and slowing down growth. Researchers knocked down the genes one at a time and in different combinations, to investigate the functional differentiation of this hormone receptor family, which is the largest in the plant kingdom. They harvested more than knowledge, however. One of the lines produced by inactivating seven genes performed amazingly well, with little change in stress tolerance and 25-31% more grain in open field trials conducted in Shanghai and Hainan Island.
By using traditional breeding methods, it would have been virtually impossible to craft the whole range of knockout combinations and find the right balance between resistance and growth. The next step will be to edit the same genes in elite varieties of rice, hoping to improve yield likewise. Meanwhile, the community of rice geneticists applauds the accomplishment. “It would have taken a hundred years without CRISPR,” says Vittoria Brambilla of the University of Milan. She used the editing tool in rice to change flowering time, a potentially interesting agronomic trait, but her plants are still in the greenhouse. “Lucky them, they can test their lines in the field. We are waiting for the authorization of national authorities since October 2016”, complains Brambilla who is caught in the regulatory impasse of GM research in Italy.
The Chinese team leader is Jian-Kang Zhu, who has a double affiliation with the Shangai Center for Plant Stress Biology and Purdue University in the US. The PNAS paper confirms China as the most active country in agricultural applications of genome editing and Oryza sativa as the most studied crop of the CRISPR era.