An Analysis of the Early Responses to Low-Temperature Stress in Oil Palm Using Integrative Physiology and Proteomics

Oil palm (Elaeis guineensis Jacq.) is a quintessential tropical oilseed crop, whose distribution and yield are significantly constrained by low-temperature stress. This study conducted physiological and proteomic analyses to investigate the early response mechanisms of one-year-old thin-shelled oil palm seedlings exposed to low temperatures of 8 °C for durations of 0, 0.5, 1, 2, 4, and 8 h. The results indicated that low-temperature treatment inhibited chlorophyll accumulation, reduced photosynthetic efficiency, and increased the levels of malondialdehyde (MDA) and soluble sugars. Concurrently, the activities of antioxidant enzymes exhibited a transient increase, suggesting an imbalance in the antioxidant defense system during the later stages of stress. Proteomics results indicate that the core pathways involved are fatty acid degradation and the regulatory pathways for starch and sucrose metabolism. Within these pathways, key proteins such as ACSL (long-chain fatty acid-CoA ligase), paaF (enoyl-CoA hydratase), HADH (3-hydroxyacyl-CoA dehydrogenase), and HADHA (enoyl-CoA hydratase/long-chain 3-hydroxyacyl-CoA dehydrogenase) are identified among 13 differential accumulation protein (DAPs). It is hypothesized that these key proteins work in concert to regulate osmosis, scavenge reactive oxygen species (ROS), stabilize membranes, and supply energy. Through physiological and proteomic analyses, this study identified physiological indicators, key proteins, and regulatory pathways associated with cold tolerance in oil palm, thus providing a theoretical basis for breeding low-temperature-tolerant oil palm varieties. The findings contribute to the development of low-temperature-tolerant oil palm cultivars.