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【Objective】Rice blast is an important limiting factor in rice production. Exploring and utilizing resistant genes is an important guarantee for achieving high and stable yield of rice. Previous studies have shown that rice blast resistance-related microRNA osa-miR-21 may regulate rice blast resistance by targeting the polyamine oxidase gene OsPAO4. However, the function of Polyamine Oxidases (PAOs) in rice disease resistance has not been reported. In order to further explore the possible biological function of OsPAO4 gene in rice disease resistance, the CRISPR/Cas9 editing technology was used for site-specific editing of ospao4 gene mutants and the edited offspring were also analyzed.【Method】A 20-bp editing target was designed in the second exon of OsPAO4, and the nucleotide fragments of the target was cloned into pRGEB32 vector to obtain OsPAO4 editing vector. Then, the rice Pik-H4 NIL callus was transformed by Agrobacterium-mediated method. Positive transgenic plants were obtained by regeneration culture and hygromycin detection, PCR and sequence analysis were performed on the DNA sequences near the target site in the T0 generation plants.【Result】The results show that the OsPAO4 gene was successfully edited and finally 25 transgenic-positive plants were obtained, and various mutation types were produced in the T0 generation, including 3 homozygous mutants, 18 heterozygous mutants and 4 nonedited plants. In addition, the glume color of the heterozygous mutation ospao4-8 of the T0 generation changed from purple to dark gray, and the activity of catalase (CAT) in the mutants was increased. It was predicted that OsPAO4 might participate in the basis immunization process.【Conclusion】A variety of ospao4 mutants were created in this study, and it was preliminarily determined that OsPAO4 might participate in the regulation of rice immune process, which laid an important foundation for further revealing the specific biological function and molecular regulation mechanism of OsPAO4 gene.

The intricate regulatory process governing rice immunity against the blast fungus Magnaporthe oryzae remains a central focus in plant–pathogen interactions. In this study, we investigated the important role of Osa-miR11117, an intergenic microRNA, in regulating rice defense mechanisms. Stem-loop qRT-PCR analysis showed that Osa-miR11117 is responsive to M. oryzae infection, and overexpression of Osa-miR11117 compromises blast resistance. Green fluorescent protein (GFP)-based reporter assay indicated OsPAO4 is one direct target of Osa-miR11117. Furthermore, qRT-PCR analysis showed that OsPAO4 reacts to M. oryzae infection and polyamine (PA) treatment. In addition, OsPAO4 regulates rice resistance to M. oryzae through the regulation of PA accumulation and the expression of the ethylene (ETH) signaling genes. Taken together, these results suggest that Osa-miR11117 is targeting OsPAO4 to regulate blast resistance by adjusting PA metabolism and ETH signaling pathways.

Bacterial leaf streak (BLS), caused by Xanthomonas oryzae pv. oryzicola (Xoc), is a bacterial disease affecting rice production in Asia and Africa, whose severity is expected to increase with climate change. Identification of new quantitative-trait loci (QTL) or resistance genes for BLS resistance is essential for developing resistant rice. A genome-wide association study to identify QTL associated with BLS resistance was conducted using phenotypic and genotypic data from 429 rice accessions. Of 47 QTL identified, 45 were novel and two co-localized with previously reported QTL or genes conferring BLS resistance. qBLS6.2 on chromosome 6 explained the greatest phenotypic variation. Combined analysis of differential expression and annotations of predicted genes near qBLS6.2 based on haplotype and disease phenotype identified OsBLS6.2 (LOC_Os06g02960) as a candidate gene for qBLS6.2. OsBLS6.2 knockout plants showed higher resistance to Xoc than wild-type plants. Many other candidate genes for resistance to Xoc were identified. [ABSTRACT FROM AUTHOR]