Integrated physiological, metabolic and molecular responses driving differential regulation of shared aluminum-resistance mechanisms in highbush blueberry.
Abstract
Aluminum (Al) toxicity constrains plant productivity on ≈30% of arable acidic soils, yet woody species show cultivar-specific regulation of conserved Al-resistance mechanisms. We dissected physiological, biochemical and molecular responses that underpin Al resistance in three highbush blueberry (Vaccinium corymbosum L.) cultivars "Cargo" (Al-tolerant), "Star" (Al-sensitive) and "Liberty" (uncharacterized). One-year-old plants were hydroponically exposed to 0, 200, 400 or 800 μM AlCl3 (pH 4.5) for 0-48 h. We quantified Al accumulation, gas exchange, antioxidant metrics, TCA-cycle enzymes (NAD-IDH, NAD-MDH) and the expression of VcMATE and VcALMT transporter genes. "Cargo" accumulated up to 18-fold more Al in roots than in shoots yet maintained photosynthetic rate (-21% at 800 μM after 48 h) and pigment integrity, coincident with a 2- to 3-fold surge in root NAD-MDH activity and stable ASC/DHA ratios. "Star" accumulated less root Al but showed marked declines in net photosynthesis (-33%) and increased lipid peroxidation (2-fold). "Liberty" displayed concentration dependent phenotypes intermediate at low to moderate Al doses (200-400 μM) but exhibiting the greatest net photosynthesis decline at 48 h (800 μM), indicated of high dose sensitivity. VcMATE was transiently repressed at 24 h in all cultivars; a transient recovery (≈2-fold at 48 h, 400 μM) was observed in "Liberty", while "Cargo" roots-maintained suppression, consistent with an internal tolerance strategy. VcALMT was generally down-regulated across cultivars and time points. Blueberry Al tolerance hinges on rapid root sequestration, sustained redox buffering and TCA-cycle up-regulation that preserves carbon flux to organic-acid detoxification. These findings provide a mechanistic framework for improving Al resistance in woody plants, with direct relevance for cultivar selection and orchard management on acid soils, particularly in volcanic regions such as southern Chile.