Lavender species are of significant economic value being cultivated extensively worldwide for their essential oils (EOs), which include terpenes that play crucial roles in the cosmetic, personal care, and pharmaceutical industries. The terpene synthases in lavender, such as Lavandula angustifolia linalool synthase (LaLINS), limonene synthase (LaLIMS), and bergamotene synthase (LaBERS), are key enzymes in terpene biosynthesis. However, the functional mechanisms underlying these enzymes remain poorly understood. Here, we used AlphaFold2 to predict the three-dimensional structures of LaLINS, LaLIMS, and LaBERS. The hydrodynamic radii of LaLINS, LaLIMS, and LaBERS were 5.7 ± 0.2, 6.2 ± 0.3, and 5.4 ± 0.2 nm, respectively. Mutations D320A or D324A led to a complete loss of activity in LaLINS compared to the wild-type (WT) enzyme; similarly, mutations D356A or D360A abolished activity in LaLIMS, and D291A or D295A eliminated activity in LaBERS. Furthermore, the genes LaLINS, LaLIMS, and LaBERS exhibited significantly higher expression levels in leaves compared to stems and flowers, with peak expression occurring at 8:00 a.m. Our findings contribute to a deeper understanding of terpene biosynthesis in lavender and offer insights for improving essential oil production through genetic engineering.

Photodynamic therapy (PDT) is recognized as a powerful method to inactivate cells. However, the photosensitizer (PS), a key component of PDT, has suffered from undesired photobleaching. Photobleaching reduces reactive oxygen species (ROS) yields, leading to the compromise of and even the loss of the photodynamic effect of the PS. Therefore, much effort has been devoted to minimizing photobleaching in order to ensure that there is no loss of photodynamic efficacy. Here, we report that a type of PS aggregate showed neither photobleaching nor photodynamic action. Upon direct contact with bacteria, the PS aggregate was found to fall apart into PS monomers and thus possessed photodynamic inactivation against bacteria. Interestingly, the disassembly of the bound PS aggregate in the presence of bacteria was intensified by illumination, generating more PS monomers and leading to an enhanced antibacterial photodynamic effect. This demonstrated that on a bacterial surface, the PS aggregate photo-inactivated bacteria via PS monomer during irradiation, where the photodynamic efficiency was retained without photobleaching. Further mechanistic studies showed that PS monomers disrupted bacterial membranes and affected the expression of genes related to cell wall synthesis, bacterial membrane integrity, and oxidative stress. The results obtained here are applicable to other types of PSs in PDT.

Volatile esters are key flavor components in most plants, including Lavandula x intermedia (lavandin). The final step in ester biosynthesis is catalyzed by Lavandula x intermedia alcohol acyltransferases (LiAATases), which attach alcohols to acyl groups. However, the functional role and mechanism of LiAATases remain poorly understood. Here, we predicted their structural models using AlphaFold2 and identified potential active site residues through the GalaxyWEB program. Catalytic assays were optimized at pH 7.5 and 30 °C. Substrate specificity for alcohols was assessed for both enzymes. Gene expression analysis revealed that LiAATase1 and LiAATase2 were most highly expressed in the petals and pistils, respectively, with peak expression occurring at stage 4 for LiAATase1 and stage 1 for LiAATase2. Our study aims to elucidate the functional properties of alcohol acyltransferases in Lavandula x intermedia, contributing to an understanding of ester biosynthesis and specificity in this species.