The CRISPR-Cas9 system depends on a guide RNA (gRNA) to specify its target.
By co-expressing multiple gRNAs, the CRISPR-Cas9 system can perform multiple
gene editing. The team of Bastian Minkenberg from Pennsylvania State
University identified the rice genes MPK1 and MPK6, homologs of Arabidopsis
genes AtMPK6 and AtMPK4, respectively, in
<[www.isaaa.org]
e> rice (Oryza sativa) as essential genes for rice development via
CRISPR-edited mutants.

The team found that MPK1 knock-out mutants were severely dwarfed and
sterile, and the homozygous mpk1 seeds from heterozygous parents were
defective in embryo development. Meanwhile, heterozygous mpk6 mutant plants
failed to produce homozygous mpk6 seeds. Both these findings prove the
importance of MPK genes in rice embryo development. However, unlike
Arabidopsis MPK genes where individual MPK genes can be turned off and have
no distinguishable effect on the phenotype, a knockout of an individual MPK
gene in rice has lethal consequences to the embryo.

This study revealed the importance of MPK1 and MPK6 in rice development. It
enables future functional studies to specify the function of each MPK gene.

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