OsMYB305 on qATS1 positively regulates alkalinity tolerance at the seedling stage in japonica rice

Main Conclusion: The major QTL qATS1 for rice seedling alkali tolerance was identified by QTL-seq and QTL mapping, and further confirmed that OsMYB305 regulates plant alkali tolerance by affecting the transport of Na⁺ and K⁺ in roots and seedlings through qRT-PCR and functional characterization. Rice is a crop sensitive to saline and alkaline stress. However, the scarcity of alkali tolerance genes in rice has resulted in a large number of cultivated rice or germplasm resources that are difficult to cultivate in saline fields. To clone new alkali tolerance genes, we systematically characterized the number of days of seedling survival and sodium and potassium ion concentrations under alkali stress using 840 F_2:3 individuals generated from a cross between Hajingdao8 and Tengxi144. Using QTL-seq technology and QTL mapping based on KASP markers, qATS1 was localized to the 77.15 Kb interval on chromosome 1. A MYB gene, OsMYB305, was identified to strongly respond to alkali stress by gene function annotation, mutation detection, and qRT-PCR analysis of this interval. Knockdown of OsMYB305 in HJD8 resulted in a massive transfer of Na⁺ and K⁺ from the mutant roots to the leaves, leading to the death of osmyb305 leaves after 18 days of alkali stress. In conclusion, this study identified OsMYB305 as an alkali tolerance gene, and the variation of 19 SNPs in the promoter region of OsMYB305 and 4 SNPs on exons can provide a theoretical basis for future search of molecular mechanisms upstream and downstream of OsMYB305 to regulate alkali tolerance and molecular design breeding.