Distribution, Development, and Function of Resin Canals in Conifers: Insights from Cellular and Genomic Perspectives

Resin canals are tunnel-like tissue structures primarily responsible for synthesizing and secreting resin. They consist of specialized secondary metabolite-synthesizing epithelial cells and supportive subsidiary cells, which are arranged to form distinctive intercellular spaces. In conifers, resin canals can develop during normal development or be induced by environmental stimuli, which often form an interconnected network and play a crucial role in defense against pathogens and insects. Despite their importance in resin secretion and defense, the mechanisms underlying their formation and function remain poorly understood. In this review, we summarize recent advances in the study of resin canals in conifers from the perspectives of cellular development, defense mechanisms, and molecular regulation. We analyze the distribution patterns, subcellular characteristics and formation and developmental processes of resin canals across different conifer species. Based on studies of traumatic resin canals, we propose a developmental model that depicts the initiation from cambial activity to cell differentiation and canal formation. Furthermore, we focus on resin canal-specific genes and analyze the functions and expression patterns of identified related genes. With the advancement of conifer genome sequencing and single-cell technologies, future research on resin canal regulatory mechanisms and functions is facing unprecedented opportunities. We propose a strategic framework aimed at enhancing conifer breeding, particularly for traits such as stress resilience, disease resistance and wood quality.