Aoxue Wang

Squalene is a triterpene with potent biological activities. Squalene (C₃₀H₅₀) is a linear polyunsaturated hydrocarbon composed of six isoprene units and six carbon–carbon double bonds. It serves as an essential precursor for sterols, steroid hormones, and vitamin D in humans and exhibits antioxidant, anti-tumor, and lipid-regulating properties. In plants, squalene is produced via the mevalonate (MVA) and 2-C-methyl-D-erythritol-4-phosphate (MEP) pathways. The key rate-limiting enzymes in these pathways include 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), farnesyl diphosphate synthase (FPS), and squalene synthase (SQS). Camellia oleifera, a unique woody oil crop native to China, is valued for its high-quality edible oil and as a rich natural source of squalene. This review provides a systematic overview of recent progress in squalene biosynthesis in C. oleifera. It summarizes the structural characteristics and biosynthetic routes. It further elaborates on the multi-level regulatory network modulated by transcription factors (WRKY, bHLH, MYB, and ERF), phytohormones (jasmonic acid, abscisic acid, and gibberellin), and abiotic factors (light and drought). Notably, this review distinguishes earlier foundational studies from recent breakthroughs and integrates emerging progress on squalene’s non-canonical functions and pathway crosstalk. It further highlights novel regulatory mechanisms unique to C. oleifera (e.g., CoWRKY15, CoMYB1, and CoMYC2). By bridging molecular regulation with practical breeding and metabolic engineering, this review lays a solid theoretical foundation for cultivating high-squalene C. oleifera varieties. It represents a prominent innovation relative to previously published studies.

To investigate the coordinated role of RALF1 and eIF4E1 within the FER signaling module in regulating root hair elongation and stress responses in Arabidopsis thaliana, we constructed a ralf1/eif4e1 double mutant via conventional hybridization. Although the roles of the RALF1 and eIF4E1 genes are well known, the simultaneous absence of them remains poorly characterized. The double mutant exhibited significantly reduced root hair numbers and elongation and heightened sensitivity to ABA, Cd²⁺, and NaCl stress. The ralf1/eif4e1 double mutant exhibited delayed flowering time and higher numbers of rosette leaves. Fluorescence quantitative PCR analyses revealed that several key genes involved in regulating flowering such as FT, LFY and SOC reached maximum levels in wild-type plants. However, other genes that regulated floral meristem exhibited higher expression levels in the ralf1 mutant, followed by in wild-type plants. This work provides new insight into the RALF1-FERONIA-eIF4E1 module, demonstrating that it converges environmental cues to coordinately regulate root hair elongation, stress responses, and flowering time in Arabidopsis.