Abstract:

Peroxidases are heme-containing oxidoreductases unique to plants that constitute a large multigene family. In this review，recent advances in plant class Ⅲ POD gene families are systematically summarized across five dimensions：gene identification，structural characterization，functional diversity，stress responsiveness，and transcriptional regulatory networks，with particular emphasis on horticultural crops. The number of POD gene family members varies dramatically among species，and family size is primarily shaped by whole-genome duplication and tandem repeat events. Phylogenetic analysis has revealed that POD proteins from multiple species can be classified into four major evolutionary clusters，each exhibiting distinct divergence in gene structure，subcellular localization，and catalytic properties. Functionally，PODs are broadly implicated in root development，stem lignification，pollen maturation，fruit ripening，and seed germination through catalysis of lignin oxidative polymerization，cross-linking of cell wall proteins，auxin oxidation，and modulation of reactive oxygen species（ROS）levels. In biotic stress responses，physical barriers are reinforced by POD-mediated lignin deposition in cell walls，while defense signaling pathways are activated through precise regulation of ROS homeostasis，thereby conferring resistance to fungal，bacterial，and viral pathogens. Under abiotic stress，adaptation to drought，salinity，cold，and heavy metal toxicity is primarily achieved through POD-dependent scavenging of excess ROS. Growing attention has also been directed toward the roles of PODs in horticultural crop quality formation，including anthocyanin metabolism，fruit lignification，and enzymatic browning. At the regulatory level，several transcription factor modules governing POD gene expression have been elucidated in rice，Arabidopsis，and sweet potato. Current knowledge gaps in POD gene research and potential applications inmolecular breeding of horticultural crops are discussed. This review provides a theoretical framework for the utilization of POD genetic resources to improve stress tolerance and quality traits in horticultural crops.

Key words: horticultural crops, peroxidase, gene family, biotic stress, abiotic stress, quality formation, molecular breeding