Work

Evolutionary divergence and functional characterization of the lavender metallothionein (LaMT) gene family in heavy metal stress tolerance

Year: 2025

Type: article

Abstract: Lavender ( Lavandula angustifolia Mill.) is valued for its essential oil and potential in phytoremediation of heavy metal-contaminated soils. Importantly, the oil remains free of metals like lead, cadmium, and zinc even when plants are grown in polluted conditions. This study systematically characterized the metallothionein (MT) gene family in lavender ( LaMT ) to understand its role in heavy metal stress response. Bioinformatics analysis identified 16 LaMT genes unevenly distributed across 12 chromosomes, classified into four subfamilies. Phylogenetic comparison of MTs from 16 species showed that seed plants, including lavender, are enriched in Type I and Type II MT subfamilies, while lower plants possess evolutionarily divergent atypical MTs. Structural and promoter analyses revealed conserved gene architectures and an abundance of abiotic stress-related cis-elements, suggesting roles in multi-hormone and stress adaptation. Expression profiling revealed tissue-specific regulatory patterns. Specifically, gene expression in leaves was induced by gibberellic acid, ethylene, light, and drought, while that in flower buds was induced by abscisic acid, methyl jasmonate, and cold. Under heavy metal stress, LaMT3C and LaMT2B were consistently upregulated across roots, stems, and leaves, highlighting their central role in stress adaptation. Heterologous expression in Escherichia coli showed that seven LaMT genes enhanced bacterial tolerance to Cu 2 + , Cd 2+ , Zn 2+ , and Mn 2+ , with LaMT1A, LaMT2C , and LaMT3C conferring the strongest effects. Transgenic Arabidopsis overexpressing LaMT3B or LaMT3C both exhibited enhanced heavy metal resistance, with LaMT3C lines denmonstrating superior performance, as evidenced by reduced malondialdehyde levels, elevated proline content, and increased antioxidant enzyme activities. Taken together, LaMT3C is the most promising candidate gene for engineering metal tolerance, functioning effectively in both bacterial and plants while displaying strong metal-induced expression in lavender. This study provides insights into the evolutionary and functional diversification of the LaMT family and establishes a foundation for developing crops with improved heavy metal tolerance. • 16 LaMT genes identified in lavender show distinct functions. • LaMT3C and LaMT2B are core genes for cross-tissue heavy metal stress tolerance. • LaMT3C enhances E. coli and Arabidopsis resistance to Cu, Cd, Zn, and Mn. • LaMTs regulate antioxidant and hormone pathways for stress adaptation. • Lavender oil retains heavy-metal-free quality even in contaminated soils.

Source: Industrial Crops and Products

DOI: 10.1016/j.indcrop.2025.122385