Effects of phytochrome-interacting factor OsPIL1 knockout on blast disease resistance in indica rice

【Objective】To clarify the effects of knockout of phytochrome-interacting factor gene（OsPIL1） in rice（Oryza sativa） on the growth, yield and disease resistance of indica rice Yuelianggu, and to preliminarily explore effects of exogenous jasmonic acid（JA） or salicylic acid（SA） on the regulation of rice blast resistance by OsPIL1, and to explore the role of OsPIL1 integrating JA/SA in regulating rice blast resistance, which could provide basic data for analyzing the mechanism of rice blast resistance. 【Method】Rice variety Yuelianggu was as material CRISPR/Cas9 technology was used to obtain OsPIL1 knockout transgenic rice line, which was analyzed for phenotypic analysis（root length, coleoptile length, plant height, tiller number, spike length, number of solid grains per spike, 100-grain weight, grain length, grain width） and assay of rice blast resistance（observation of blast symptom and infection process） in inoculated rice plants, as well as for the analysis of rice blast resistance in inoculated rice plants after exogenous JA/SA treatment. 【Result】Three pure OsPIL1 knockout transgenic rice lines （ΔOspil1 ko #7, #33 and #36） were acquired by CRISPR/Cas9. These OsPIL1 knockout transgenic rice lines exhibited lower in various agronomic traits, including plant height, tiller number, root length, coleo-ptile length, distance from the stem base to the new leaf sheath junction, panicle length, grain number per panicle, length from the panicle node to the top leaf sheath junction, internode length, 100-grain weight, grain length and grain width than those of the wild type. Compared with the wild type, the activity of peroxidase（POD） in the OsPIL1 knockout transgenic rice lines changed slightly, but the content of reactive oxygen species（ROS） increased significantly while the content of lignin decreased significantly（P＜0.05, the same below）, and the expression levels of chloroplasts and defense related genes in rice changed. The symptoms of rice blast in OsPIL1 knockout transgenic rice lines infected with Magnaporthe oryzae were aggravated. Compared with the wild type inoculated with Magnaporthe oryzae, the disease index of OsPIL1 knockout transgenic rice lines was significantly increased, the number of callose changed slightly, the number of dead cells and ROS content increased, the activity of POD and the content of lignin decreased, and the expression level of defense related genes decreased. Inoculation with live injury caused by Magnaporthe oryzae into OsPIL1 knockout rice lines led to a significant increase in the relative growth of fungi in individual lesions, further confirming the reduced resistance to rice blast in OsPIL1 knockout transgenic rice lines. Exogenous JA or SA could greatly enhance the resistance of OsPIL1 knockout transgenic rice lines to rice blast, but the improvement effect was inferior to that of JA or SA on the resistance to rice blast in wild type rice. 【Conclusion】OsPIL1 knockout negatively affects rice growth, grain development and rice blast resistance, and OsPIL1 regulates JA or SA pathway to improve rice blast resistance in indica rice.