**Mutation of** *Inositol 1,3,4-trisphosphate 5*/*6-kinase6* **Impairs Plant Growth and Phytic Acid Synthesis in Rice**

### **Meng Jiang 1,2,3 , Yang Liu 1, Yanhua Liu 1, Yuanyuan Tan 1, Jianzhong Huang 1,3 and Qingyao Shu 1,2,\***


Received: 20 March 2019; Accepted: 24 April 2019; Published: 29 April 2019

**Abstract:** Inositol 1,3,4-trisphosphate 5/6-kinase (ITPK) is encoded by six genes in rice (*OsITPK1-6*). A previous study had shown that nucleotide substitutions of *OsITPK6* 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 *OsITPK6* mutant lines were generated by targeted mutagenesis of the gene's first exon using the CRISPR/Cas9 method, one (*ositpk6\_1*) with a 6-bp in-frame deletion, and other three with frameshift mutations (*ositpk6\_2*, \_*3*, and \_*4*). The frameshift mutations severely impaired plant growth and reproduction, while the effect of *ositpk6\_1* was relatively limited. The mutant lines *ositpk6\_1* and \_*2* 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 *ositpk6\_1* also showed less tolerance to osmotic stresses. Our research demonstrates that mutations of *OsITPK6*, while effectively reducing phytic acid biosynthesis in rice grain, could significantly impair plant growth and reproduction.

**Keywords:** genome editing; growth; *ositpk6*; phytic acid; rice
