Abstract
BACKGROUND: Ilex verticillata belongs to the genus Ilex of the family Aquifoliaceae. It has extremely high ornamental value, and its drought tolerance is crucial for expanding its cultivation range. Therefore, studying the metabolic regulation mechanism of I. verticillata in response to drought stress at different stages under natural drought conditions provides a basis for the expanded cultivation of I. verticillata and important theoretical support for the drought-resistant breeding of woody plants. METHODS: Two-year-old cutting seedlings (0.3~0.4 m high) of I. verticillata were used as experimental materials. A control group (normal watering) and a drought treatment group (natural drought after watering by the basin immersion method) were set up. Leaves were collected at the non-drought stage, and after 10, 20, and 30 days of drought and 1 day of rehydration for metabolomic analysis. RESULTS: I. verticillata showed an obvious gradient of physiological responses under drought stress: the relative water content and chlorophyll content of leaves decreased gradually from the normal level and increased gradually after rehydration; the activity of antioxidant enzymes and the content of malondialdehyde increased continuously with the extension of drought stress and decreased significantly after rehydration. Metabolomic analysis revealed that the content of most lipid metabolites was down-regulated in the early stage of drought, which might reduce peroxidative damage by decreasing lipid synthesis; all lipid metabolites were up-regulated in the late stage of drought to alleviate stress by enhancing membrane stability; most lipid metabolites remained up-regulated after rehydration, promoting membrane structure reconstruction. CONCLUSIONS: The lipid metabolism of I. verticillata under drought stress presents a typical "first inhibition then promotion" pattern. Glycerophospholipid metabolism is a common metabolic pathway under both drought and rehydration conditions, which proves that this metabolic pathway is closely related to the drought-resistant characteristics of I. verticillata.