Molecular Mechanisms of Insect-Resistant Function in Leaf Glandular Hairs of Different Wild Hazel Species Revealed by Integrated Transcriptomic and Metabolomic Analysis
Abstract
As an important economic forest tree species, hazel exhibits remarkable insect resistance in natural environments, with leaf glandular trichomes likely serving as key physical and chemical defense barriers. However, the molecular mechanisms underlying this insect resistance remain poorly understood. This study selected three wild hazel variants (E5, E7, and ED) displaying distinct glandular trichome morphologies and integrated transcriptomic and non-targeted metabolomic approaches to systematically analyze gene expression and metabolite accumulation in leaf glandular trichomes. Results revealed substantial interspecific variations in glandular trichome morphology, density, chemical composition, and metabolic pathways among the three variants. E5 exhibited high trichome density with pale purple pigmentation. Although key flavonoid biosynthesis genes were significantly upregulated, flavanol accumulation remained low, whereas pronounced accumulation of kaempferol suggested a metabolic redirection mechanism. In contrast, E7 and ED displayed lower trichome density and a transparent appearance. Despite reduced expression of flavonoid pathway genes, both accumulated substantial flavanols and related compounds, indicating a constitutive storage strategy. Galactose metabolism analysis further revealed distinct carbon allocation strategies among variants to support insect resistance. This study demonstrates that flavonoid and galactose metabolic pathways play pivotal roles in regulating insect resistance in hazel leaf glandular trichomes, providing a theoretical basis for understanding insect resistance mechanisms in forest trees and supporting resistance breeding efforts.
