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• Epigenetic mosaicism is a possible source of within-plant phenotypic heterogeneity, yet its frequency and developmental origin remain unexplored. This study examines whether extant epigenetic heterogeneity within Lavandula latifolia (Lamiaceae) shrubs reflects recent epigenetic modifications experienced independently by different plant parts or, alternatively, it is the cumulative outcome of a steady lifetime process. • Leaf samples from different architectural modules (branch tips) were collected from three L. latifolia plants and characterized epigenetically by global DNA cytosine methylation and methylation state of methylation-sensitive amplified fragment-length polymorphism (MS-AFLP) markers. Epigenetic characteristics of modules were then assembled with information on the branching history of plants. Methods borrowed from phylogenetic research were used to assess genealogical signal of extant epigenetic variation and reconstruct within-plant genealogical trajectory of epigenetic traits. • Plants were epigenetically heterogeneous, as shown by differences among modules in global DNA methylation and variation in the methylation states of 6 to 8% of MS-AFLP markers. All epigenetic features exhibited significant genealogical signal within plants. Events of epigenetic divergence occurred throughout the lifespan of individuals and were subsequently propagated by branch divisions. • Internal epigenetic diversification of L. latifolia individuals took place steadily during their development, a process which eventually led to persistent epigenetic mosaicism.

The Lavandula genus, which includes lavender (Lavandula angustifolia) and lavandin (L. angustifolia × Lavandula latifolia), is cultivated worldwide for its essential oils, which find applications in perfumes, cosmetics, food processing and, more recently, in aromatherapy products. The chemical composition of lavender and lavandin essential oils, usually produced by steam distillation from the flowering stems, is characterized by the presence of terpenes (e.g. linalool and linalyl acetate) and terpenoids (e.g. 1,8-cineole), which are mainly responsible for their characteristic flavour and their biological and therapeutic properties. Lavender and lavandin distilled straws, the by-products of oil extraction, were traditionally used for soil replenishment or converted to a fuel source. They are mineral- and carbon-rich plant residues and, therefore, a cheap, readily available source of valuable substances of industrial interest, especially aroma and antioxidants (e.g. terpenoids, lactones and phenolic compounds including coumarin, herniarin, α-bisabolol, rosmarinic and chlorogenic acids). Accordingly, recent studies have emphasized the possible uses of lavender and lavandin straws in fermentative or enzymatic processes involving various microorganisms, especially filamentous fungi, for the production of antimicrobials, antioxidants and other bioproducts with pharmaceutical and cosmetic activities, opening up new challenging perspectives in white biotechnology applications.

Polyploidization and transposon elements contribute to shape plant genome diversity and secondary metabolic variation in some edible crops. However, the specific contribution of these variations to the chemo‐diversity of Lamiaceae, particularly in economic shrubs, is still poorly documented. The rich essential oils (EOs) of Lavandula plants are distinguished by monoterpenoids among the main EO‐producing species, L. angustifolia (LA), L. × intermedia (LX) and L. latifolia (LL). Herein, the first allele‐aware chromosome‐level genome was assembled using a lavandin cultivar ‘Super’ and its hybrid origin was verified by two complete subgenomes (LX‐LA and LX‐LL). Genome‐wide phylogenetics confirmed that LL, like LA, underwent two lineage‐specific WGDs after the γ triplication event, and their speciation occurred after the last WGD. Chloroplast phylogenetic analysis indicated LA was the maternal source of ‘Super’, which produced premium EO (higher linalyl/lavandulyl acetate and lower 1,8‐cineole and camphor) close to LA. Gene expression, especially the monoterpenoid biosynthetic genes, showed bias to LX‐LA alleles. Asymmetric transposon insertions in two decoupling ‘Super’ subgenomes were responsible for speciation and monoterpenoid divergence of the progenitors. Both hybrid and parental evolutionary analysis revealed that LTR (long terminal repeat) retrotransposon associated with AAT gene loss cause no linalyl/lavandulyl acetate production in LL, and multi‐ BDH copies retained by tandem duplication and DNA transposon resulted in higher camphor accumulation of LL. Advances in allelic variations of monoterpenoids have the potential to revolutionize future lavandin breeding and EO production.

Key messageWe isolated and functionally characterized a new ( +)-bornyl diphosphate synthase (( +)-LiBPPS) from Lavandula x intermedia. The in planta functions of ( +)-LiBPPS were evaluated in sense and antisense transgenic plants.The monoterpene ( +)-borneol contributes scent and medicinal properties to some plants. It also is the immediate precursor to camphor, another important determinant of aroma and medicinal properties in many plants. ( +)-Borneol is generated through the dephosphorylation of bornyl diphosphate (BPP), which is itself derived from geranyl diphosphate (GPP) by the enzyme ( +)-bornyl diphosphate synthase (( +)-BPPS). In this study we isolated and functionally characterized a novel ( +)-BPPS cDNA from Lavandula x intermedia. The cDNA excluding its transit peptide was expressed in E. coli, and the corresponding recombinant protein was purified with Ni–NTA agarose affinity chromatography. The recombinant ( +)-LiBPPS catalyzed the conversion of GPP to BPP as a major product, and a few minor products. We also investigated the in planta role of ( +)-LiBPPS in terpenoid metabolism through its overexpression in sense and antisense orientations in stably transformed Lavandula latifolia plants. The overexpression of ( +)-LiBPPS in antisense resulted in reduced production of ( +)-borneol and camphor without compromising plant growth and development. As anticipated, the overexpression of the gene led to enhanced production of borneol and camphor, although growth and development were severely impaired in most transgenic lines strongly and ectopically expressing the ( +)-LiBPPS transgene in sense. Our results demonstrate that LiBPPS would be useful in studies aimed at the production of recombinant borneol and camphor in vitro, and in metabolic engineering efforts aimed at lowering borneol and camphor production in plants. However, overexpression in sense may require a targeted expression of the gene in glandular trichomes using a trichome-specific promoter.

Lamiaceae is one of the largest families of aromatic plants and it is characterized by the presence of external glandular structures which produce essential oils highly valued in cosmetics and medicine. Plants of Lavandula latifolia, Mentha piperita, Salvia sclarea, Salvia lavandulifolia, Thymus capitatus, and Thymus mastichina were grown for one year. In order to evaluate the effects of drought stress, plants were subjected to two water treatments (100% ETo and 70% ETo, including the rainfall during the experimental period). At the end of the experiment, the biomass, the essential oil content, and leaf nutrients concentration were assessed for each water treatment and species studied. At the end of the experiment, L. latifolia, M. piperita and T. capitatus plants showed a significant fresh weight reduction under drought stress conditions whereas the other species studied remained unchanged. With respect to dry weight, only L. latifolia plants showed a reduction under water deficit conditions. As far as essential oil content was concerned, L. latifolia and S. sclarea plants had a reduction under water deficit conditions. Leaf nutrient concentration showed different trends between species considering the nutrient assessed. The economic viability of the growth of this species will be dependent on the benefits achieved which are related to yield production obtained and the price accorded for both raw material and the essential oil extracted.

Natural extracts as biostimulants have the potential to enhance the productivity and growth of many medicinal and aromatic plants. This study aimed to enhance the growth, and essential oil (EO) content, as well as composition of Lavandula latifolia Medik. by using Malva parviflora L. extract (ME) as a biostimulant in combination with humic acid (HA) in a field experiment in two successive seasons of 2022 and 2023. The phenolic, flavonoid and water-soluble vitamins of the ME were analyzed using an HPLC. The protein amino acids of the ME were identified by an amino acid analyzer. The prepared concentrations of HA (0, 1, 2, and 4 g/L) were applied to the soil. While, they for ME (0, 2, 4, and 6 g/L) were added as a foliar spray. The EO compositions collected from the leaves of the treated L. latifolia plants were subjected to the hydro-distillation method and analyzed using GC-MS. The most prevalent vitamins found in ME were vitamin B12, vitamin C, and folic acid. Besides, several phenolic compounds were found in ME, such as catechol, cinnamic acid and syringic acid, while flavonoid chemicals, such as luteolin and quercetin. Also, alanine, ammonia, aspartic acid, glutamic acid, glycine, and tyrosine were the ME’s most prominent nitrogenous and amino acid components. The most effective treatments of HA and ME on the plant height, the number of branches/plant, and plant fresh weight were 4 + 6 g/L and 4 + 2 g/L for leaf area and chlorophyll content, it was 4 + 4 g/L; and for EO percentage were 4 + 0 g/L, 2 + 0 g/L, and 4 + 4 g/L, compared to the control treatment for each characteristic. The main EO compounds eucalyptol, camphor, α -pinene, β -pinene, Δ-elemene, germacrene D-4-ol, isoborneol, β -caryophyllene oxide, and tau.-cadinol identified in the leaves were found in the range of 28.74–46.19%, 15.34–30.49%, 3.39–7.16%, 0–5.08%, 0–5.18%, 0–3.20%, 0–3.31% and 0–3.40%, respectively. It can be concluded that a combination treatment of HA and ME as natural biostimulant compounds at 4 + 4 g/L could be recommended for good plant growth, and EO quantity of L. latifolia plants.

Sub-individual variation in traits of homologous structures has multiple ecological consequences for individuals and populations. Assessing the evolutionary significance of such effects requires an improved knowledge of the mechanisms underlying within-plant phenotypic heterogeneity. The hypothesis that continuous within-plant variation in some phenotypic traits can be associated with epigenetic mosaicism was examined. Fifteen individuals of the long-lived, evergreen Mediterranean shrub Lavandula latifolia were studied. Five widely spaced 'modules', each consisting of a single inflorescence plus all its subtending basal leaves, were collected from each shrub. Genomic DNA was extracted from leaf samples and genome-wide cytosine methylation determined by reversed phase high-performance liquid chromatography (HPLC) with spectrofluorimetric detection. The number and mean mass of seeds produced were determined for each inflorescence. An assessment was made of whether (1) leaves from different modules in the same plant differed significantly in global DNA cytosine methylation, and (2) mosaicism in cytosine methylation contributed to explain variation across modules in number and size of seeds. Leaves from different modules in the same plant differed in global DNA cytosine methylation. The magnitude of epigenetic mosaicism was substantial, as the variance in DNA methylation among modules of the same shrub was greater than the variance between individuals. Number and mean mass of seeds produced by individual inflorescences varied within plants and were quadratically related to cytosine methylation of subtending leaves, with an optimum at an intermediate methylation level (approx. 25 %). The results support a causal link between global cytosine methylation of leaves in a module and the size and numbers of seeds produced by the associated inflorescence. It is proposed that variation in global DNA methylation within L. latifolia shrubs may result from the concerted action of plant sectoriality and differential exposure of different plant parts to some environmental factor(s) with a capacity to induce durable epigenetic changes.

Spike lavender, Lavandula latifolia Medik., is a species of economic importance for its essential oil (EO). The purpose of this study was to estimate the effect of the variable climate and fixed factors such as soil and geographic location on EO yield and quality. The study material was collected in 34 populations from four different Spanish bioregions for three years. The EO extraction from spike lavender leaves and flowers was done with simple hydrodistillation, in Clevenger. Soil samples were also collected. Climate data were provided by the State Meteorological Agency. The EO average yield was obtained for the bioregion mean and in each bioregion. The higher EO yield is related clearly to the climate condition. A greater amount of annual rainfall produced a higher EO yield in the four bioregions and of better quality. Soils richer in organic matter and minerals produced higher EO yield but with less quality. The altitude had little effect on EO yield. Higher altitude favored obtaining higher EO quality. At lower latitude, further south, the populations obtained a higher EO yield. The evaluation of the environmental effect on the EO yield and quality could allow better natural conservation and more accurate selection of the best populations for breeding and spike lavender cultivation protocols.

Premise of the Study The ecological and evolutionary significance of natural epigenetic variation (i.e., not based on DNA sequence variants) variation will depend critically on whether epigenetic states are transmitted from parents to offspring, but little is known on epigenetic inheritance in nonmodel plants. Methods We present a quantitative analysis of transgenerational transmission of global DNA cytosine methylation (= proportion of all genomic cytosines that are methylated) and individual epigenetic markers (= methylation status of anonymous MSAP markers) in the shrub Lavandula latifolia. Methods based on parent‐offspring correlations and parental variance component estimation were applied to epigenetic features of field‐growing plants (‘maternal parents’) and greenhouse‐grown progenies. Transmission of genetic markers (AFLP) was also assessed for reference. Key Results Maternal parents differed significantly in global DNA cytosine methylation (range = 21.7–36.7%). Greenhouse‐grown maternal families differed significantly in global methylation, and their differences were significantly related to maternal origin. Methylation‐sensitive amplified polymorphism (MSAP) markers exhibited significant transgenerational transmission, as denoted by significant maternal variance component of marker scores in greenhouse families and significant mother‐offspring correlations of marker scores. Conclusions Although transmission‐related measurements for global methylation and MSAP markers were quantitatively lower than those for AFLP markers taken as reference, this study has revealed extensive transgenerational transmission of genome‐wide global cytosine methylation and anonymous epigenetic markers in L. latifolia. Similarity of results for global cytosine methylation and epigenetic markers lends robustness to this conclusion, and stresses the value of considering both types of information in epigenetic studies of nonmodel plants.

The main aim of this study was to investigate the effects of inhaled lavender aromatherapy on depression and anxiety levels among postmenopausal women. A randomized clinical trial was performed in which 46 postmenopausal women received 2% inhaled lavender essence or distilled water 20 minutes nightly before bedtime for 4 successive weeks. Depression and anxiety mean scores decreased in the lavender group compared with controls, providing evidence that lavender aromatherapy may be an effective noninvasive treatment during the postmenopausal stage. •The present study observed the effects of inhaling aromatherapy for anxiety and depression in postmenopausal women in a short-term period.•Inhalation aromatherapy with 2% lavender essential oil for 20 minutes over a 4-week period proved to be effective for depression with a significant reduction in depressive symptoms after the intervention.•All participants had completed the aromatherapy treatment during 4 weeks and were involved in their care. This shows that they had trusted the nurse practitioners’ recommendations.