Analysis of the Mechanisms of Rice oszfp30 Mutant in Improving Forage-Quality-Related Traits Based on Transcriptome and Metabolome Analyses

Background/Objectives: Using straw as feed is crucial for addressing resource scarcity and waste-based environmental pollution and alleviating the contradiction between forage production and food security. However, rice straw has disadvantages such as a high lignin, cellulose, and hemicellulose content, as well as a dense cell wall structure, which greatly limit its utilization as feed. Improving the forage quality of rice straw through genetic breeding is an important means of enhancing its utilization rate. Methods: To explore the molecular basis underlying the improved nutritional and cell wall compositional traits of the rice lines (oszfp30-1 and oszfp30-2) obtained in previous studies, we conducted phenotypic, physiological, transcriptomic, and metabolomic analyses on oszfp30-1, oszfp30-2 and the wild type (WT) after 50 days of pot cultivation. Results: oszfp30-1 and oszfp30-2 exhibited higher plant height, above-ground biomass, crude protein, and crude fat content, while their hemicellulose, cellulose, and lignin contents were significantly lower than those of the wild type. Transcriptomics was used to identify 737 common differentially expressed genes (DEGs), and metabolomics was used to identify 189 common differentially expressed metabolites (DEMs). KEGG analysis revealed that these DEGs and DEMs were significantly enriched in terpene biosynthesis, starch and sucrose metabolism, phenylpropanoid biosynthesis, and amino sugar and nucleotide sugar metabolism. Conclusions: Our research reveals that the improvement in forage-quality-related traits is closely related to key genes involved in gibberellin synthesis, including GA20ox, GA2ox, and GA3ox; key genes involved in cellulose synthesis, including OsSUS and UGPase; key genes involved in hemicellulose synthesis, including UXS and IRX10; and key genes involved in lignin synthesis, including CCR, CAD, CCoAOMT, and COMT. These identified DEGs and DEMs are associated with the OsZFP30 mutation and may be downstream targets of this transcription factor, providing a foundation for further research on the OsZFP30 regulatory network.