OsFK1 encodes C-14 sterol reductase, which is involved in sterol biosynthesis and affects premature aging of leaves in rice

The enzyme C-14 sterol reductase is involved in biosynthesis of brassinosteroids (BR) and sterols, as well as plant development. , a member of the sterol biosynthesis pathway located in the endoplasmic reticulum (ER), encodes C-14 sterol reductase. However, there is little research on the function of C-14 sterol reductase in rice. Compared with the wild type, an mutant showed dwarf phenotype and premature aging in the second leaf during the trefoil stage, and abnormal development of leaf veins during the tillering stage. The mutant showed signs of aberrant PCD, as evidenced by TUNEL staining. This suggested that high ROS buildup caused DNA damage and ROS-mediated cell death in the mutant. The mutant also showed decreased chlorophyll content and aberrant chloroplast structure. Sequencing of the mutant allele revealed a non-synonymous G to A mutation in the final intron, leading to early termination. Here, we identified the allele, cloned it by Mutmap sequencing, and verified it by complementation. HPLC-MS/MS assays demonstrated that the mutation caused lower phytosterol levels. These findings showed that the allele encoding C-14 sterol reductase is involved in phytosterol biosynthesis and mediates normal development of rice plants.