Novel Wx alleles generated by base editing for improvement of rice grain quality

Amylose content (AC), which is regulated by the Waxy (Wx) gene, is a major indicator of eating and cooking quality (ECQ) in rice (Oryza sativa). Thus far, only a limited number of mutations in the N-terminal domain of Wx were found to have a major impact on the AC of rice grains and no mutations with such effects were reported for other regions of the Wx protein. Here, nucleotide substitutions in the middle region of Wx were generated by adenine and cytosine base editors. The nucleotide substitutions led to changes in 15 amino acid residues of Wx, and a series of novel Wx alleles with ACs of 0.3%-29.43% (wild type with AC of 19.87%) were obtained. Importantly, the waxy(abe2) allele showed a soft rice AC, improved ECQ, favorable appearance, and no undesirable agronomic traits. The transgenes were removed from the waxy(abe2) progeny, generating a promising breeding material for improving rice grain quality.

Automated summary

Novel alleles of the Waxy gene, including the waxy(abe2) allele, were generated by nucleotide substitutions in the middle region of the Wx protein, leading to improvements in amylose content and cooking quality of rice grains. The waxy(abe2) allele exhibited desirable characteristics without undesirable agronomic traits, providing a promising breeding material for enhancing rice grain quality.