Postharvest warm conditioning associates with HMGR abundance, squalene accumulation, and MAPK/phosphatase transcriptional responses in Camellia oleifera

Introduction Fully mature Camellia oleifera fruits undergo a brief postharvest warm-conditioning step that can markedly affect oil quality and squalene levels, yet its early molecular basis remains unclear. Methods We integrated transcriptomics, UPLC–MS/MS metabolomics, targeted biochemical assays, and RT–qPCR to profile seed-kernel tissues collected from fruits incubated at 35 °C and 95% RH for 0, 12, and 24 h. Results Warm conditioning increased squalene content and HMGR abundance in seed-kernel tissues. RNA-seq revealed broad transcriptional reprogramming, including coordinated changes in mevalonate pathway-associated genes and multiple phosphorylation-related components. Among four HMGR transcripts, HMGR-2 showed the highest baseline abundance, whereas HMGR-1 showed the strongest relative induction at 12 h, as confirmed by RT–qPCR. In parallel, MPK3/MPK6-like kinases and PP1/PP2A subunits were transcriptionally responsive to the treatment. Discussion These multi-omic and biochemical data define an early postharvest warm-conditioning response associated with increased HMGR abundance and squalene accumulation, while providing candidate genes and pathway context for future functional validation.