Mutation of Impairs Plant Growth and Phytic Acid Synthesis in Rice.

Inositol 1,3,4-trisphosphate 5/6-kinase (ITPK) is encoded by six genes in rice (). A previous study had shown that nucleotide substitutions of could significantly lower the phytic acid content in rice grains. In the present study, the possibility of establishing a genome editing-based method for breeding low-phytic acid cultivars in rice was explored, in conjunction with the functional determination of OsITPK6. Four mutant lines were generated by targeted mutagenesis of the gene's first exon using the CRISPR/Cas9 method, one () with a 6-bp in-frame deletion, and other three with frameshift mutations (, _, and _). The frameshift mutations severely impaired plant growth and reproduction, while the effect of was relatively limited. The mutant lines and _ had significantly lower levels (-10.1% and -32.1%) of phytic acid and higher levels (4.12- and 5.18-fold) of inorganic phosphorus compared with the wild-type (WT) line. The line also showed less tolerance to osmotic stresses. Our research demonstrates that mutations of , while effectively reducing phytic acid biosynthesis in rice grain, could significantly impair plant growth and reproduction.