CRISPR-mediated Knockout of SaF/SaM Overcomes the Hybrid Male Sterility in Rice

Hybrids between the indica and japonica subspecies of rice (Oryza sativa) are usually sterile, which hinders the use of heterosis in the inter-subspecific hybrid breeding. The complex locus Sa comprises two adjacently located genes, SaF and SaM, which interact to cause abortion of pollen grains carrying the japonica allele in japonica-indica hybrids. In this study, Yongyao Xie of the South China Agricultural University aims to restore male fertility in indica-japonica hybrids via silencing of SaF or SaM.

RNA interference restored male fertility in indica-japonica hybrids with heterozygous Sa. The team then used CRISPR-Cas9 genome editing to knockout the SaF and SaM alleles of an indica rice line to create hybrid-compatible lines. The resultant alleles did not affect pollen viability and other agricultural traits, but broke down the reproductive barrier in the hybrids. They also found that some rice lines have natural neutral allele Sa-n, which was compatible with the typical japonica or indica alleles in hybrids.

This study provides basis for the generation of hybrid-compatible lines by knocking out the Sa locus or using the natural Sa-n allele to overcome hybrid male sterility in rice breeding.

For more information, read the article in Journal of Integrative Plant Biology.