An ,,,, Mutant with a 33-nt Deletion Showed Enhanced Tolerance to Salt and Drought Stress in Rice.

encodes inositol 1,3,4,5,6-pentaphosphate 2-kinase, which catalyzes the conversion of -inositol-1,3,4,5,6-pentaphosphate to -inositol-1,2,3,4,5,6-hexaphosphate (IP) in rice. By clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein (Cas9)-mediated mutagenesis in the 3rd exon of the gene, three mutations, i.e., (a 33-nt deletion), (a 1-nt deletion), and (a 2-nt deletion) were identified in T plants of the rice line Xidao #1 (wild type, WT). A transfer DNA free line with the homozygous mutation was developed; however, no homozygous mutant lines could be developed for the other two mutations. The comparative assay showed that the mutant line had a significantly lower level of phytic acid (PA, IP; -19.5%) in rice grain and agronomic traits comparable to the WT. However, the mutant was more tolerant to salt and drought stresses than the WT, with significantly lower levels of inositol triphosphate (IP), reactive oxygen species (ROS) and induced IP, and higher activities of antioxidant enzymes in seedlings subjected to these stresses. Further analyses showed that the transcription of stress response genes was significantly upregulated in the mutant under stress. Thus, the low phytic acid mutant should have potential applications in rice breeding and production.