Integrated multi-omics analysis identifies OsMYB48 as a transcriptional repressor of coleoptile elongation in anaerobic rice germination

Direct seeding of rice (DS) has been widely adopted due to reduced labor cost and simpler cultivation practices. However, anaerobic flooding conditions reduce seed germination and seedling establishment. Here, a genome-wide association study (GWAS) of four coleoptile traits using 572 rice accessions subjected to 3 d of anaerobic conditions was conducted. The traits were coleoptile length (CL), coleoptile surface area (CSA), coleoptile volume (CV), and coleoptile diameter (CD). Ninety two QTL were identified, with 59 overlapping with previously reported loci. Two rice varieties (C126 and C261) with contrasting coleoptile lengths were selected for multi-omics analyses. A specific anaerobic-responsive blue module was identified by weighted gene co-expression network analysis (WGCNA). Thirty six candidate genes were screened, including OsMYB48 that was predominantly localized in the nucleus. Loss-of-function OsMYB48 mutants exhibited significantly increased coleoptile length relative to the control under 4 d of anaerobic conditions. Endogenous hormone measurements revealed that the content of 1-aminocyclopropanecarboxylic acid (ACC), the ethylene precursor, was significantly increased in the ko-osmyb48-1 mutants. Ethylene-related genes OsACS1 and OsACO2 were also upregulated in the mutants. OsMYB48 DAP-seq identified 31 potential target genes, including WB1 and OsBURP16. Hence, anaerobic-responsive gene OsMYB48 likely acts as a transcriptional repressor of coleoptile elongation under anaerobic germination conditions, probably via the ethylene signaling pathway. This work provides a theoretical basis and genetic resources for breeding rice lines with high germination when directly sown.