The CISPR-Cas9 system is a powerful tool for site-directed mutagenesis in
crops. The team of Yuhei Kanazashi from Hokkaido University in Japan were
successful in performing a simultaneous site-directed mutagenesis in two
homoeologous loci in soybeann (Glycine max), GmPPD1 and GmPPD2. These two
genes are orthologs of Arabidopsis thaliana PEAPOD (PPD) gene.
Most of the T1 plants generated had mutations in at least one of the
targeted loci. Analysis of T1 generation indicates that the mutations
induced in the T0 plant can be inherited by the T1 generation. The team also
induced new mutations in T1 plants, which were then also detected in the T2
generation. This indicates that continuous induction of mutations during T1
plant development could increase the occurrence of mutations in germ cells.
Mutations in both GmPPD loci were also confirmed in at least 33% of the T2
seeds examined. The mutants with mutations in both GmPPD1 and GmPPD2
exhibited dome-shaped trifoliate leaves, extremely twisted pods, and
produced few seeds.
These results suggest that continuous induction of mutations in the
succeeding generations of genome-edited plants can increase the efficiency
of mutagenesis in duplicated loci in soybean.