Discovery of MPK Roles in Rice by Characterizing CRISPR-Edited Mutants

The CRISPR-Cas9 system depends on a guide RNA (gRNA) to specify its target. Efficiently co-expressing multiple gRNAs that target different genomic sites enables multiple gene editing in the family of closely related mitogen-activated protein kinase (MPK) genes in rice (Oryza sativa).

The team from Pennsylvania State University identified MPK1 and MPK6, orthologs of Arabidopsis AtMPK6 and AtMPK4, respectively, as essential genes for rice development using CRISPR-edited mutants. The true knock-out mutants of MPK1 were severely dwarfed and sterile. While heterozygous mutants were able to produce seeds, homozygous mpk1 seeds were defective in embryo development. Meanwhile, heterozygous mpk6 mutant plants failed to produce homozygous mpk6 seeds.

The CRISPR-Cas9 system had a 45–86% frequency for the successful creation of mutants while simultaneously targeting two to eight genomic sites. The mutations were also stably inherited in the next generation.

This study reveals the importance of MPK1 and MPK6 in rice development. CRISPR-Cas9 technology enabled the functional discovery of genes or domains with phenotypes masked by plant death.

For more on this study, read the article in The Plant Journal.