Comparative proteomic analysis of desiccation responses in recalcitrant Quercus acutissima seeds

The preservation of recalcitrant seeds is crucial for sustainable forest management and biodiversity conservation, particularly for economically important species like Quercus acutissima. However, these seeds pose serious challenges for ex situ conservation due to their high sensitivity to desiccation. This study employed integrated physiological, cytological, and proteomic approaches to systematically reveal the characteristics of viability loss during desiccation of Q. acutissima seeds. The results showed that fresh seeds had an initial moisture content of 38.8% (IM) with a germination percentage of 99%, while the semi-lethal (SLM) and lethal moisture (LM) contents were 26.8% and 14.8%, respectively. Desiccation caused cell wall collapse, membrane system rupture, and cytoplasmic degradation, while physiological and proteomic results revealed distinct responses during different desiccation stages. In the early stages, downregulation of iron superoxide dismutase indicated antioxidant system impairment, while lipoxygenase-mediated membrane lipid peroxidation triggered reactive oxygen species and malondialdehyde accumulation. During the deep desiccation stages (LM), we observed active energy metabolism with isocitrate dehydrogenase [NADP] upregulation. Additionally, the downregulation of phospholipase D and acyl-CoA synthetase may promote abnormal accumulation of free fatty acids; these factors collectively exacerbated membrane system disintegration. Furthermore, the glutathione-ascorbic acid cycle failed at later stages, translation mechanisms were imbalanced (ribosomal protein upregulation and tRNA synthetase downregulation), programmed cell death -related proteins were upregulated, while protective protein systems (insufficient late embryogenesis abundant expression and delayed small heat shock protein response) failed to effectively mitigate damage. The results suggest that the desiccation sensitivity of Q. acutissima seeds stems from a multi-cascade reaction involving oxidative damage, membrane system collapse, translation dysregulation, and programmed cell death. This study provides a theoretical basis for optimizing recalcitrant seed preservation strategies: comprehensive approaches should include antioxidant protection, membrane stabilization techniques, and metabolic regulation to holistically address multi-system damage during desiccation.