Comparative transcriptome provides new insights to the molecular regulation of olive trees to chilling stress.

Olive (Olea europaea. L), an economically important oil-producing crop, is sensitive to low temperature, which severely limits its productivity and geographical distribution. However, the underlying mechanism of cold tolerance in olive remains elusive. In this study, a chilling experiment (4 °C) on the living saplings of two olive cultivars revealed that O. europaea cv. Arbequina showed stronger cold tolerance with greater photosynthetic activity compared to O. europaea cv. Leccino. Transcriptome analyses revealed that early light-inducible protein 1 (ELIP1), the main regulator for chlorophyll synthesis, is dramatically induced to protect the photosynthesis at low temperatures. Furthermore, weighted gene co-expression network analysis (WGCNA), yeast one-hybrid (Y1H), and luciferase (LUC) assays demonstrated that transcription factor bHLH66 serves as an important regulator of ELIP1 transcription by binding to the G-box motif in the promoter. Taken together, our research revealed a novel transcriptional module consisting of bHLH66- ELIP1 in the adaptation of olive trees to cold stress.

An easy methodology for frost tolerance assessment in olive cultivars.

Introduction: Olive cultivation, like other evergreen fruit crops worldwide, is limited by the occurrence of frost episodes in different times of the year, mainly in winter or early spring. Some contradictory results are reported about cultivars' response to frost, which depends on the physiological stage of the tissues (acclimated or not acclimated) when the cold or frost episode occurs. This work aimed to implement a user-friendly and reliable lab method for discerning frost tolerance. Methods: Our methodology considered both detached leaves and potted plantlets. The optimal temperature at which damage differentiated between cultivars was evaluated, as well as the time of exposure to cold and the recovery time for the correct evaluation of the symptoms. Furthermore, a comparative analysis of damage on both young and mature leaves was conducted. To validate the efficacy of the methodology, assessments were conducted on the cultivars 'Arbequina' (tolerant), 'Picual' (moderately tolerant), and 'Frantoio' (susceptible) under acclimated and non-acclimated conditions. Results and discussion: The results indicated that, when detached leaves were used for frost evaluation, a temperature of -10°C ± 1°C for 30 min and a recovery time at 26°C for 24-48 h after exposure to cold are enough to induce damages on the leaves and discriminate between cultivar susceptibility. Under these conditions, a precise assessment of symptoms can be made, facilitating the categorization of frost tolerance level in various olive cultivars. Notably, no significant differences were observed between young and mature leaves during the evaluation process. On the other hand, the critical temperature to assess damages on potted plantlets was determined to be -7°C ± 1°C. In addition, it was observed that acclimated plants exhibited fewer symptoms compared to non-acclimated ones, with 'Frantoio' being the most affected alongside 'Picual' and 'Arbequina'. Conclusion: The implemented methodology will allow the assessment of frost tolerance in several olive cultivars within a short timeframe, and it is proven to be user-friendly and reliable.

Comparative metabolomics of leaves and stems of three Italian olive cultivars under drought stress.

The Mediterranean will be one of the focal points of climate change. The predicted dry and hot summers will lead to water scarcity in agriculture, which may limit crop production and growth. The olive tree serves as a model woody plant for studying drought stress and improving water resource management; thus, it is critical to identify genotypes that are more drought tolerant and perform better under low irrigation or even rainfed conditions. In this study, the metabolomic approach was used to highlight variations in metabolites in stems and leaves of three Italian olive cultivars (previously characterized physiologically) under two and four weeks of drought stress. Phenolic and lipophilic profiles were obtained by gas chromatography-mass spectrometry and ultra-high performance liquid chromatography-mass spectrometry, respectively. The findings identified the leaf as the primary organ in which phenolic variations occurred. The Maurino cultivar exhibited a strong stress response in the form of phenolic compound accumulation, most likely to counteract oxidative stress. The phenolic compound content of 'Giarraffa' and 'Leccino' plants remained relatively stable whether they were exposed to drought or not. Variations in the lipid profile occurred in leaves and stems of all the cultivars. A high accumulation of compounds related to epicuticular wax components was observed in the leaf of 'Giarraffa', while a strong reduction of lipids and long-chain alkanes occurred in 'Maurino' when exposed to drought stress conditions.

Morphological and Pigment Responses to Far-Red and Photosynthetically Active Radiation in an Olive Cultivar Suitable for Super-High-Density Orchards.

Plant density is increasing in modern olive orchards to improve yields and facilitate mechanical harvesting. However, greater density can reduce light quantity and modify its quality. The objective was to evaluate plant morphology, biomass, and photosynthetic pigments under different red/far-red ratios and photosynthetically active radiation (PAR) combinations in an olive cultivar common to super-high-density orchards. In a greenhouse, young olive trees (cv. Arbequina) were exposed to low (L) or high (H) PAR with or without lateral FR supplementation (L+FR, L-FR, H+FR, H-FR) using neutral-density shade cloth and FR light-emitting diode (LED) modules. Total plant and individual organ biomass were much lower in plants under low PAR than under high PAR, with no response to +FR supplementation. In contrast, several plant morphological traits, such as main stem elongation, individual leaf area, and leaf angle, did respond to both low PAR and +FR. Total chlorophyll content decreased with +FR when PAR was low, but not when PAR was high (i.e., a significant FR*PAR interaction). When evaluating numerous plant traits together, a greater response to +FR under low PAR than under high PAR appeared to occur. These findings suggest that consideration of light quality in addition to quantity facilitates a fuller understanding of olive tree responses to a light environment. The +FR responses found here could lead to changes in hedgerow architecture and light distribution within the hedgerow.

Olive Tree Belowground Microbiota: Plant Growth-Promoting Bacteria and Fungi.

The olive tree is one of the most significant crops in the Mediterranean region. Its remarkable adaptability to various environments has facilitated olive cultivation across diverse regions and agricultural scenarios. The rising global demand for olive products, coupled with climate challenges, is driving changes in cultivation methods. These changes are altering the traditional landscape and may potentially reshape the structure and composition of orchard microbial communities, which can impact productivity and stress tolerance. Bacterial and fungal communities naturally associated with plants have long been recognized as crucial for plant growth and health, serving as a vital component of sustainable agriculture. In this review, we aim to highlight the significance of olive cultivation and the impact of abiotic stresses. We update the current knowledge on the profiles of rhizosphere and root fungal and bacterial communities in olive orchards and examine how (a)biotic factors influence these communities. Additionally, we explore the potential of plant growth-promoting bacteria and fungi in enhancing olive physiological performance and stress tolerance. We identify knowledge gaps and emphasize the need for implementing new strategies. A comprehensive understanding of olive-associated microbiota will aid in developing sustainable agronomic practices to address climatic challenges and meet the growing demand for olive products.

Comprehensive Review of Olea europaea: A Holistic Exploration into Its Botanical Marvels, Phytochemical Riches, Therapeutic Potentials, and Safety Profile.

Human health is now inextricably linked to lifestyle choices, which can either protect or predispose people to serious illnesses. The Mediterranean diet, characterized by the consumption of various medicinal plants and their byproducts, plays a significant role in protecting against ailments such as oxidative stress, cancer, and diabetes. To uncover the secrets of this natural treasure, this review seeks to consolidate diverse data concerning the pharmacology, toxicology, phytochemistry, and botany of Olea europaea L. (O. europaea). Its aim is to explore the potential therapeutic applications and propose avenues for future research. Through web literature searches (using Google Scholar, PubMed, Web of Science, and Scopus), all information currently available on O. europaea was acquired. Worldwide, ethnomedical usage of O. europaea has been reported, indicating its effectiveness in treating a range of illnesses. Phytochemical studies have identified a range of compounds, including flavanones, iridoids, secoiridoids, flavonoids, triterpenes, biophenols, benzoic acid derivatives, among others. These components exhibit diverse pharmacological activities both in vitro and in vivo, such as antidiabetic, antibacterial, antifungal, antioxidant, anticancer, and wound-healing properties. O. europaea serves as a valuable source of conventional medicine for treating various conditions. The findings from pharmacological and phytochemical investigations presented in this review enhance our understanding of its therapeutic potential and support its potential future use in modern medicine.

Identification and Evaluation of Olive Phenolics in the Context of Amine Oxidase Enzyme Inhibition and Depression: In Silico Modelling and In Vitro Validation.

The Mediterranean diet well known for its beneficial health effects, including mood enhancement, is characterised by the relatively high consumption of extra virgin olive oil (EVOO), which is rich in bioactive phenolic compounds. Over 200 phenolic compounds have been associated with Olea europaea, and of these, only a relatively small fraction have been characterised. Utilising the OliveNetTM library, phenolic compounds were investigated as potential inhibitors of the epigenetic modifier lysine-specific demethylase 1 (LSD1). Furthermore, the compounds were screened for inhibition of the structurally similar monoamine oxidases (MAOs) which are directly implicated in the pathophysiology of depression. Molecular docking highlighted that olive phenolics interact with the active site of LSD1 and MAOs. Protein-peptide docking was also performed to evaluate the interaction of the histone H3 peptide with LSD1, in the presence of ligands bound to the substrate-binding cavity. To validate the in silico studies, the inhibitory activity of phenolic compounds was compared to the clinically approved inhibitor tranylcypromine. Our findings indicate that olive phenolics inhibit LSD1 and the MAOs in vitro. Using a cell culture model system with corticosteroid-stimulated human BJ fibroblast cells, the results demonstrate the attenuation of dexamethasone- and hydrocortisone-induced MAO activity by phenolic compounds. The findings were further corroborated using human embryonic stem cell (hESC)-derived neurons stimulated with all-trans retinoic acid. Overall, the results indicate the inhibition of flavin adenine dinucleotide (FAD)-dependent amine oxidases by olive phenolics. More generally, our findings further support at least a partial mechanism accounting for the antidepressant effects associated with EVOO and the Mediterranean diet.

Supercritical Impregnation of PETG with Olea europaea Leaf Extract: Influence of Operational Parameters on Expansion Degree, Antioxidant and Mechanical Properties.

PETG (poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate)) is an amorphous copolymer, biocompatible, recyclable, and versatile. Nowadays, it is being actively researched for biomedical applications. However, proposals of PETG as a platform for the loading of bioactive compounds from natural extract are scarce, as well as the effect of the supercritical impregnation on this polymer. In this work, the supercritical impregnation of PETG filaments with Olea europaea leaf extract was investigated, evaluating the effect of pressure (100-400 bar), temperature (35-55 °C), and depressurization rate (5-50 bar min-1) on the expansion degree, antioxidant activity, and mechanical properties of the resulting filaments. PETG expansion degree ranged from ~3 to 120%, with antioxidant loading ranging from 2.28 to 17.96 g per 100 g of polymer, corresponding to oxidation inhibition values of 7.65 and 66.55%, respectively. The temperature and the binary interaction between pressure and depressurization rate most affected these properties. The mechanical properties of PETG filaments depended greatly on process variables. Tensile strength values were similar or lower than the untreated filaments. Young's modulus and elongation at break values decreased below ~1000 MPa and ~10%, respectively, after the scCO2 treatment and impregnation. The extent of this decrease depended on the supercritical operational parameters. Therefore, filaments with higher antioxidant activity and different expansion degrees and mechanical properties were obtained by adjusting the supercritical processing conditions.

Effects of fermentation and alkalisation on the formation of endocannabinoid-like compounds in olives.

The increasing interest in endocannabinoid-like compounds (ECL) in food stems from their important physiological roles, including energy metabolism and satiety. In this study, the effect of fermentation or alkalisation on the formation of ECL compounds in table olives was investigated. N-acylethanolamines, monoacylglycerols, N-acylamino acids, and N-acylneurotransmitters were monitored. Results revealed that alkaline treatment led to a significant increase in the concentrations of N-oleoylethanolamide (80%), N-palmitoylethanolamide (93%), N-linoleoylethanolamide (51%), and 1-oleoylglycerol (679%) compared to control. While N-oleoylethanolamide, N-palmitoylethanolamide, N-linoleoylethanolamide, 1- and 2-oleoylglycerol, 1- and 2-linoleoylglycerol, and oleoylphenylalanine were initially absent or present in trace amounts, their levels significantly rose during fermentation. The formation rate of these compounds was higher in olives fermented in water than those in brine. The study provides detailed information on how specific ECL compounds respond to different processing methods, offering valuable information for optimising table olive production to enhance its nutritional benefits.

Molecular sensitization profile to grass and olive pollens in Portugal.

Summary: Background. Grass and olive pollens have overlapping pollination periods and are common allergens in the Iberian Peninsula. The objective is to determine the sensitization pattern to major Phleum pratense and Olea europaea pollens in the Portuguese population with pollen allergic rhinitis (AR) using molecular allergen diagnosis (MAD). Methods. Seasonal AR patients (≥ 12 years), with positive skin prick tests (SPT) to Phleum and Olea were recruited from 16 centers. Using ALEX2, specific IgE to Phl p1, Phl p2, Phl p5, Phl p6, Phl p7, Phl p 12, Ole e1, Ole e7 and Ole e9 were determined. Immunoblotting of Olea allergic patients was performed. Results. Included 175 patients (55.4% female; mean age 31.6 ± 13.3 years; 85.7% adults; 40% asthmatic, Coast 28%/Inland 72% and North 29.1%/Centre 20.6%/South 50.3%). Considering Phleum MAD, 85.7% were sensitized to Phl p1, 45.7% to Phl p2, 50.3% to Phl p5, 45.7%, to Phl p6, 10.9% to Phl p7 and 22.9% to Phl p12. Sensitization to Ole e1 was found in 56.6%, to Ole e7 in 1.7% and Ole e9 in 3.4% patients. Sensitization to Phl p7 was more frequent in asthmatics (17.4% vs 6.6%; p = 0.044). Sensitization to Phl p5, Phl p6, Phl p12 and Ole e1 was more frequent in inland. Regarding sensitization patterns: 53.1% patients were sensitized to both species genuine´ sIgE, 38.3% to Phleum and 3.4% only to Olea species' sIgE. Immunoblotting of Olea allergic patients showed a high intensity band that may correspond to Ole e12. Conclusions. MAD showed "genuine" Grass and Olea sensitization in approximately 50% of our patients.

Analysis of heaping-induced decline in olive quality: insights from integrated analysis between phenotypic traits and gene expression profiles.

Heaping is an unavoidable process before olive milling, and its duration significantly affects the olive quality. However, there is limited research on the quality changes of olive fruits on a short-time scale. To gain a better understanding of the molecular mechanisms underlying postharvest deterioration of olives, this study piled olives at room temperature and extracted oil at 0, 8, 24, 48 and 72 h to analyze oil quality parameters. Gas/Liquid Chromatography-Mass Spectrometry (GC/LC-MS) techniques were employed to investigate variations in metabolite contents. Concurrently, the transcriptional profiles of olives during heaping were examined. As piling time progressed, quality indicators declined, and stored fruit were categorized into three groups based on their quality characters: '0 h' belongs to the first category, '8 h' and '24 h' to the second category, and '48 h' and '72 h' to the third category. Metabolite changes were consistent with the expression patterns of genes related to their synthesis pathways. Additionally, ethylene was identified as a crucial factor influencing fruit senescence. These findings establish a foundation for further research on olive deterioration after harvesting and offer insights for optimizing olive oil production.

Polyphenol-Rich Extracts from Agroindustrial Waste and Byproducts: Results and Perspectives According to the Green Chemistry and Circular Economy.

Polyphenols are natural secondary metabolites found in plants endowed with multiple biological activities (antioxidant, anti-inflammatory, antimicrobial, cardioprotective, and anticancer). In view of these properties, they find many applications and are used as active ingredients in nutraceutical, food, pharmaceutical, and cosmetic formulations. In accordance with green chemistry and circular economy strategies, they can also be recovered from agroindustrial waste and reused in various sectors, promoting sustainable processes. This review described structural characteristics, methods for extraction, biological properties, and applications of polyphenolic extracts obtained from two selected plant materials of the Mediterranean area as olive (Olea europaea L.) and pomegranate (Punica granatum L.) based on recent literature, highlighting future research perspectives.

Simultaneous Exposure to Noise and Toluene Induces Oxidative and Inflammatory Damage in the Heart of Wistar Rats: Therapeutic Potential of Olea europaea L. Leaf Extract.

Workers in occupational settings often face simultaneous exposure to multiple risk factors, including noise and chemicals. This study aimed to investigate the effects of combined exposure to noise and toluene on the cardiac health of rats, with a focus on assessing the potential mitigating effects of Olea europaea L. (OLE) leaf extract (40 mg/kg/day). The evaluation involved scrutinizing biochemical and hematological markers, quantifying oxidative stress levels, determining proinflammatory cytokines in the serum, and conducting an in silico Docking studies. Forty-two male Wistar rats were divided into eight groups-(n = 6/group):-Control-group-(C),-OLE-group-(Rats administered OLE), NT-group (rats co-exposed to noise and toluene), NT-4 group-(rats co-exposed to noise and toluene four weeks after the exposure period), NT + OLE1-group (rats co-exposed to noise and toluene treated with OLE for one week), NT + OLE2-group-(rats co-exposed to noise and toluene treated with OLE for two weeks), NT + OLE3-group-(rats co-exposed to noise and toluene treated with OLE for three weeks), and NT + OLE4-group (rats co-exposed to noise and toluene treated with OLE for four weeks). The results revealed that combined exposure to noise and toluene led to oxidative damage and increased serum levels of proinflammatory cytokines. However, OLE treatment attenuated these effects by reducing lipid peroxidation and enhancing catalase and superoxide dismutase activities. Additionally, OLE treatment significantly decreased proinflammatory cytokine levels compared to the noise and toluene co-exposed group. The study highlighted the potential of OLE to attenuate the adverse effects of combined exposure to noise and toluene, attributed to its anti-inflammatory and antioxidant properties.

Metabolome classification of olive by-products from different oil presses providing insights into its potential health benefits and valorization as analyzed via multiplex MS-based techniques coupled to chemometrics.

INTRODUCTION: The Olive (Olea europaea L.) is one of the most popular edible oil-producing fruits, consumed worldwide for its myriad nutritional and health benefits. Olive oil production generates huge quantities of by-products from the fruit, which are considered environmental hazards. Recently, more and more efforts have been made to valorize olive by-products as a source of low-cost, value-added food applications. OBJECTIVE: The main objective of this study was to globally assess the metabolome of olive fruit by-products, including olive mill wastewater, olive pomace, and olive seeds from fruits from two areas, Siwa and Anshas, Egypt. METHODS: Gas chromatography-mass spectrometry (GC-MS) and ultra-high-performance liquid chromatography with mass spectrometry (UPLC-MS) were used for profiling primary and secondary metabolites in olive by-products. Also, multivariate data analyses were used to assess variations between olive by-product samples. RESULTS: A total of 103 primary metabolites and 105 secondary metabolites were identified by GC-MS and UPLC-MS, respectively. Fatty acids amounted to a major class in the olive by-products at 53-91%, with oleic acid dominating, especially in the pomace of Siwa. Mill wastewater was discriminated from other by-products by the presence of phenolics mainly tyrosol, hydroxyl tyrosol, and α-tocopherol as analyzed by UPLC-MS indicating their potential antioxidant activity. Pomace and seeds were rich in fatty acids/esters and hydroxy fatty acids and not readily distinguishable from each other. CONCLUSION: The current work discusses the metabolome profile of olive waste products for valorization purposes. Pomace and seeds were enriched in fatty acids/esters, though not readily distinguishable from each other.

HS-SPME-GC-MS and Chemometrics for the Quality Control and Clustering of Monovarietal Extra Virgin Olive Oil: A 3-Year Study on Terpenes and Pentene Dimers of Italian Cultivars.

Terpenes and pentene dimers are less studied volatile organic compounds (VOCs) but are associated with specific features of extra virgin olive oils (EVOOs). This study aimed to analyze mono- and sesquiterpenes and pentene dimers of Italian monovarietal EVOOs over 3 years (14 cultivars, 225 samples). A head space-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method recently validated was used for terpene and pentene dimer quantitation. The quantitative data collected were used for both the characterization and clustering of the cultivars. Sesquiterpenes were the molecules that most characterized the different cultivars, ranging from 3.908 to 38.215 mg/kg; different groups of cultivars were characterized by different groups of sesquiterpenes. Pentene dimers (1.336 and 3.860 mg/kg) and monoterpenes (0.430 and 1.794 mg/kg) showed much lower contents and variability among cultivars. The application of Kruskal-Wallis test-PCA-LDA-HCA to the experimental data allowed defining 4 clusters of cultivars and building a predictive model to classify the samples (94.3% correct classification). The model was further tested on 33 EVOOs, correctly classifying 91% of them.

Oleuropein impact on colorectal cancer.

Colorectal cancer (CRC) is considered the third most common cancer in the world. In Mediterranean region, olives and olive oil play a substantial role in diet and medical traditional behaviors. They totally believe that high consumption of olive products can treat a wide range of diseases and decrease risk of illness. Oleuropein is the main active antioxidant molecule found in pre-mature olive fruit and leaves. Recently, it has been demonstrated that oleuropein is used in cancer therapy as an anti-proliferative and apoptotic agent for some cancer cells. In this review, we would like to explore the conclusive effects of oleuropein on CRC with respect to in vitro and in vivo studies.

Olive reproductive biology: implications for yield, compatibility conundrum, and environmental constraints.

Olive (Olea europaea L.) is an important Mediterranean tree species with a longstanding history of cultivation, boasting a diverse array of local cultivars. While traditional olive orchards are valued for their cultural and aesthetic significance, they often face economic sustainability challenges in the modern context. The success of both traditional and newly introduced cultivars (e.g. those obtained by cross-breeding) is hindered by self-incompatibility, a prevalent issue for this species that results in low fruit set when limited genetic diversity is present. Further, biological, environmental, and agronomic factors have been shown to interlink in shaping fertilization patterns, hence impacting on the final yield. Climatic conditions during pollination, such as excessive rainfall or high temperatures, can further exacerbate the problem. In this work, we provide an overview of the various factors that trigger the phenomenon of suboptimal fruit set in olive trees. This work provides a comprehensive understanding of the interplay among these factors, shedding light on potential mechanisms and pathways that contribute to the observed outcomes in the context of self-incompatibility in olive.

The dynamic changes in olive fruit phenolic metabolism and its contribution to the activation of quiescent Colletotrichum infection.

Anthracnose, the most critical disease affecting olive fruits, is caused by Colletotrichum species. While developing olive fruits are immune to the pathogen regardless of the cultivar, the resistance level varies once the fruit ripens. The defense mechanisms responsible for this difference in resistance are not well understood. To explore this, we analyzed the phenolic metabolic pathways occurring in olive fruits and their susceptibility to the pathogen during ripening in two resistant cultivars ('Empeltre' and 'Frantoio') and two susceptible cultivars ('Hojiblanca' and 'Picudo'). Overall, resistant cultivars induced the synthesis of aldehydic and demethylated forms of phenols, which highly inhibited fungal spore germination. In contrast, susceptible cultivars promoted the synthesis of hydroxytyrosol 4-O-glucoside during ripening, a compound with no antifungal effect. This study showed that the distinct phenolic profiles between resistant and susceptible cultivars play a key role in determining olive fruit resistance to Colletotrichum species.

A hemizygous supergene controls homomorphic and heteromorphic self-incompatibility systems in Oleaceae.

Self-incompatibility (SI) has evolved independently multiple times and prevents self-fertilization in hermaphrodite angiosperms. Several groups of Oleaceae such as jasmines exhibit distylous flowers, with two compatibility groups each associated with a specific floral morph.1 Other Oleaceae species in the olive tribe have two compatibility groups without associated morphological variation.2,3,4,5 The genetic basis of both homomorphic and dimorphic SI systems in Oleaceae is unknown. By comparing genomic sequences of three olive subspecies (Olea europaea) belonging to the two compatibility groups, we first locate the genetic determinants of SI within a 700-kb hemizygous region present only in one compatibility group. We then demonstrate that the homologous hemizygous region also controls distyly in jasmine. Phylogenetic analyses support a common origin of both systems, following a segmental genomic duplication in a common ancestor. Examination of the gene content of the hemizygous region in different jasmine and olive species suggests that the mechanisms determining compatibility groups and floral phenotypes (whether homomorphic or dimorphic) in Oleaceae rely on the presence/absence of two genes involved in gibberellin and brassinosteroid regulation.