Malate metabolism in horticultural crops: mechanistic insights and agricultural practices for quality improvement

Malate metabolism bridges plant evolutionary adaptation and fruit quality regulation, serving dual roles in energy metabolism (tricarboxylic acid cycle/glycolysis) and environmental stress responses (stomatal control, pH balance). In horticulture, apple malate content dictates flavor profiles, driving divergent consumer preferences (high-sugar in Asia vs. tartness in the West), necessitating precision breeding targeting vacuolar accumulation mechanisms. Recent bioinformatic studies and transporter biology (e.g., Ma1, ALMT) have revealed genetic regulators of malate homeostasis, yet transcriptional regulation and post-translational modifications (PTMs) of transporters remain poorly understood. Notably, cultivated varieties exhibit distinct malate-related traits compared to their wild relatives, a divergence attributable to artificial selection during domestication. Additionally, agroecological factors including light, temperature, and soil conditions, dynamically regulate malate biosynthesis and storage. This metabolic plasticity reflects evolutionary adaptations influenced by domestication. This review integrates molecular physiology and domestication genetics to dissect cross-scale regulation of malate networks. We propose a transporter-engineering framework for developing market-tailored varieties and highlight unresolved questions, including PTM-mediated transporter regulation and metabolic plasticity modeling for climate-resilient crops. Bridging evolutionary adaptation with quality-driven breeding targeting malate, this synthesis advances strategies for sustainable horticulture in shifting agroclimatic landscapes.