A Scoping Review on Carotenoid Profiling in Passiflora spp.: A Vast Avenue for Expanding the Knowledge on the Species.

The Passiflora genus is recognised for its ethnopharmacological, sensorial, and nutritional significance. Yet, the screening of its dietary and bioactive molecules has mainly targeted hydrophilic metabolites. Following the PRISMA-P protocol, this review assessed the current knowledge on carotenoid composition and analysis within Passiflora, examining 968 records from seven databases and including 17 studies focusing on carotenoid separation and identification in plant parts. Those publications originated in America and Asia. P. edulis was the most frequently examined species of a total of ten, while pulp was the most studied plant part (16 studies). Carotenoid analysis involved primarily high-performance liquid chromatography separation on C18 columns and detection using diode array detectors (64.71%). Most studies identified the provitamin A ß-carotene and xanthophylls lutein and zeaxanthin, with their geometric configuration often neglected. Only one study described carotenoid esters. Besides the methodology's insufficient description, the lack of use of more accurate techniques and practices led to a high risk of bias in the carotenoid assignment in 17.65% of the articles. This review highlights the opportunity to broaden carotenoid studies to other species and parts within the diverse Passiflora genus, especially to wild, locally available fruits, which may have a strategic role in enhancing food diversity and security amidst climatic changes. Additionally, it urges the use of more accurate and efficient analytical methods based on green chemistry to better identify Passiflora carotenoids.

Changes in the expression of genes encoding xanthophyl acyltransferases during the postharvest ripening of avocado (Persea americana) fruit.

BACKGROUND: Avocado fruit is rich in xanthophylls, which have been related to positive effects on human health. Xanthophyl acetyltransferases (XATs) are enzymes catalyzing the esterification of carboxylic acids to the hydroxyl group of the xanthophyll molecule. This esterification is thought to increase the lipophilic nature of the xanthophyll and its stability in a lipophilic environment. Studies on XATs in fruits are very scarce, and no studies had been carried out in avocado fruit during postharvest. The objective of this work was to investigate the changes in the expression of genes encoding XAT, during avocado fruit ripening. RESULTS: Avocado fruits were obtained from a local market and stored at 15 °C for 8 days. The fruit respiration rate, ethylene production, and fruit peel's color space parameters (L*, a*, b*) were measured during storage. Fruit mesocarp samples were taken after 1, 3, 5, and 7 days of storage and frozen with liquid nitrogen. Total RNA was extracted from fruit mesocarp, and the quantification of the two genes designated as COGE_ID: 936743791 and COGE_ID: 936800185 encoding XATs was performed with real-time quantitative reverse transcription polymerase chain reaction using actin as a reference gene. The presence of a climacteric peak and large changes in color were recorded during postharvest. The two genes studied showed a large expression after 3 days of fruit storage. CONCLUSIONS: We conclude that during the last stages of ripening in avocado fruit there was an active esterification of xanthophylls with carboxylic acids, which suggests the presence of esterified xanthophylls in the fruit mesocarp. © 2024 Society of Chemical Industry.

Microbial chassis as the platform for production of dihydroxy xanthophyll-based carotenoids: an overview of recent advances in biomanufacturing.

Physiological and environmental cues prompt microbes to synthesize diverse carotenoids, including dihydroxy xanthophylls, facilitating their adaptation and survival. Lutein and its isomeric counterpart, zeaxanthin, are notable dihydroxy xanthophylls with bioactive properties such as antioxidative, anti-inflammatory, anticancer, and neuroprotective effects, particularly beneficial for human ocular health. However, global natural resources for co-producing lutein and zeaxanthin are scarce, with zeaxanthin lacking commercial sources, unlike lutein sourced from marigold plants and microalgae. Traditionally, dihydroxy xanthophyll production primarily relies on petrochemical synthetic routes, with limited biological sourcing reported. Nonetheless, microbiological synthesis presents promising avenues as a commercial source, albeit challenged by low dihydroxy xanthophyll yield at high cell density. Strategies involving optimization of physical and chemical parameters are essential to achieve high-quality dihydroxy xanthophyll products. This overview briefly discusses dihydroxy xanthophyll biosynthesis and highlights recent advancements, discoveries, and industrial benefits of lutein and zeaxanthin production from microorganisms as alternative biofactories.

Macular Pigment Optical Density and Skin Carotenoids in a Childhood Sample.

BACKGROUND: Carotenoids are plant pigments with light filtering and antioxidant properties that deposit in human tissues, including retina and skin. Descriptive characteristics and covariates of carotenoid status in macula and skin have been examined in adults; however, similar studies in children are limited. Thus, this study aimed to delineate how factors of age, sex, race, weight status, and dietary carotenoid intake relate to macular and skin carotenoids in children. METHODS: Children (7-13 y, N = 375) completed heterochromatic flicker photometry to assess macular pigment optical density (MPOD). Participants underwent anthropometrics to measure weight status (BMI percentile [BMI%]), and parent/guardian provided demographic information. Subsample data were available for skin carotenoids (N = 181), assessed using reflection spectroscopy, and dietary carotenoids (N = 101) using the Block Food Frequency Questionnaire. Relationships between skin and macular carotenoids were assessed using partial Pearson's correlations controlling for age, sex, race, and BMI%. Relationships between dietary carotenoids and macular and skin carotenoids were assessed using stepwise linear regression including age, sex, race, and BMI% in the model. RESULTS: Mean MPOD was 0.56 ± 0.22 and skin carotenoid score was 282 ± 94.6. There was no significant correlation between MPOD and skin carotenoids (r = 0.02, P = 0.76). BMI% was negatively associated with skin (stdß = -0.42, P < 0.001), but not macular carotenoids (stdß = -0.04, P = 0.70). Neither MPOD nor skin carotenoids were associated with age, sex, or race (all P > 0.10). MPOD was positively associated with energy-adjusted reported lutein + zeaxanthin intake (stdß = 0.27, P = 0.01). Skin carotenoids were positively associated with energy-adjusted reported carotenoid intake (stdß = 0.26, P = 0.01). CONCLUSIONS: The mean MPOD values in children were higher than what has been reported in adult populations. Previous studies in adult samples report an average MPOD of 0.21. Although macular and skin carotenoids were not related, they were associated with dietary carotenoids relevant to the respective tissues; however, skin carotenoids may be more susceptible negative influence from higher weight status.

Effect of carotenoids on gut health and inflammatory status: A systematic review of in vivo animal studies.

Carotenoids have anti-inflammatory and antioxidant properties, being a potential bioactive compound for gut health. The objective of this systematic review was to investigate the effects of carotenoids on gut microbiota, gut barrier, and inflammation in healthy animals. The systematic search from PubMed, Scopus, and Lilacs databases were performed up to March 2023. The final screening included thirty studies, with different animal models (mice, rats, pigs, chicks, drosophila, fish, and shrimp), and different carotenoid sources (ß-carotene, lycopene, astaxanthin, zeaxanthin, lutein, and fucoxanthin). The results suggested that carotenoids seem to act on gut microbiota by promoting beneficial effects on intestinal bacteria related to both inflammation and SCFA production; increase tight junction proteins expression, important for reducing intestinal permeability; increase the mucins expression, important in protecting against pathogens and toxins; improve morphological parameters important for digestion and absorption of nutrients; and reduce pro-inflammatory and increase anti-inflammatory cytokines. However, different carotenoids had distinct effects on gut health. In addition, there was heterogeneity between studies regarding animal model, duration of intervention, and doses used. This is the first systematic review to address the effects of carotenoids on gut health. Further studies are needed to better understand the effects of carotenoids on gut health.

Seasonal Monitoring of Volatiles and Antioxidant Activity of Brown Alga Cladostephus spongiosus.

Cladostephus spongiosus was harvested once a month during its growing season (from May to August) from the Adriatic Sea. Algal volatile organic compounds (VOCs) were obtained by headspace solid-phase microextraction (HS-SPME) and hydrodistillation (HD) and analysed by gas chromatography and mass spectrometry (GC-MS). The effects of air drying and growing season on VOCs were determined. Two different extraction methods (ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE)) were used to obtain ethanolic extracts of C. spongiosus. In addition, the seasonal antioxidant potential of the extracts was determined, and non-volatile compounds were identified from the most potent antioxidant extract. Aliphatic compounds (e.g., pentadecane) were predominantly found by HS-SPME/GC-MS. Hydrocarbons were more than twice as abundant in the dry samples (except in May). Aliphatic alcohols (e.g., hexan-1-ol, octan-1-ol, and oct-1-en-3-ol) were present in high percentages and were more abundant in the fresh samples. Hexanal, heptanal, nonanal, and tridecanal were also found. Aliphatic ketones (octan-3-one, 6-methylhept-5-en-2-one, and (E,Z)-octa-3,5-dien-2-one) were more abundant in the fresh samples. Benzene derivatives (e.g., benzyl alcohol and benzaldehyde) were dominant in the fresh samples from May and August. (E)-Verbenol and p-cymen-8-ol were the most abundant in dry samples in May. HD revealed aliphatic compounds (e.g., heptadecane, pentadecanal, (E)-heptadec-8-ene, (Z)-heptadec-3-ene), sesquiterpenes (germacrene D, epi-bicyclosesquiphellandrene, gleenol), diterpenes (phytol, pachydictyol A, (E)-geranyl geraniol, cembra-4,7,11,15-tetraen-3-ol), and others. Among them, terpenes were the most abundant (except for July). Seasonal variations in the antioxidant activity of the ethanolic extracts were evaluated via different assays. MAE extracts showed higher peroxyl radical inhibition activity from 55.1 to 74.2 µM TE (Trolox equivalents). The highest reducing activity (293.8 µM TE) was observed for the May sample. Therefore, the May MAE extract was analysed via high-performance liquid chromatography with high-resolution mass spectrometry and electrospray ionisation (UHPLC-ESI-HRMS). In total, 17 fatty acid derivatives, 9 pigments and derivatives, and 2 steroid derivatives were found. The highest content of pheophorbide a and fucoxanthin, as well as the presence of other pigment derivatives, could be related to the observed antioxidant activity.

The Clinical Promise of Microalgae in Rheumatoid Arthritis: From Natural Compounds to Recombinant Therapeutics.

Rheumatoid arthritis (RA) is an invalidating chronic autoimmune disorder characterized by joint inflammation and progressive bone damage. Dietary intervention is an important component in the treatment of RA to mitigate oxidative stress, a major pathogenic driver of the disease. Alongside traditional sources of antioxidants, microalgae-a diverse group of photosynthetic prokaryotes and eukaryotes-are emerging as anti-inflammatory and immunomodulatory food supplements. Several species accumulate therapeutic metabolites-mainly lipids and pigments-which interfere in the pro-inflammatory pathways involved in RA and other chronic inflammatory conditions. The advancement of the clinical uses of microalgae requires the continuous exploration of phytoplankton biodiversity and chemodiversity, followed by the domestication of wild strains into reliable producers of said metabolites. In addition, the tractability of microalgal genomes offers unprecedented possibilities to establish photosynthetic microbes as light-driven biofactories of heterologous immunotherapeutics. Here, we review the evidence-based anti-inflammatory mechanisms of microalgal metabolites and provide a detailed coverage of the genetic engineering strategies to enhance the yields of endogenous compounds and to develop innovative bioproducts.

The Endless World of Carotenoids-Structural, Chemical and Biological Aspects of Some Rare Carotenoids.

Carotenoids are a large and diverse group of compounds that have been shown to have a wide range of potential health benefits. While some carotenoids have been extensively studied, many others have not received as much attention. Studying the physicochemical properties of carotenoids using electron paramagnetic resonance (EPR) and density functional theory (DFT) helped us understand their chemical structure and how they interact with other molecules in different environments. Ultimately, this can provide insights into their potential biological activity and how they might be used to promote health. In particular, some rare carotenoids, such as sioxanthin, siphonaxanthin and crocin, that are described here contain more functional groups than the conventional carotenoids, or have similar groups but with some situated outside of the rings, such as sapronaxanthin, myxol, deinoxanthin and sarcinaxanthin. By careful design or self-assembly, these rare carotenoids can form multiple H-bonds and coordination bonds in host molecules. The stability, oxidation potentials and antioxidant activity of the carotenoids can be improved in host molecules, and the photo-oxidation efficiency of the carotenoids can also be controlled. The photostability of the carotenoids can be increased if the carotenoids are embedded in a nonpolar environment when no bonds are formed. In addition, the application of nanosized supramolecular systems for carotenoid delivery can improve the stability and biological activity of rare carotenoids.

Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and Melanin.

In the retina, retinoids involved in vision are under constant threat of oxidation, and their oxidation products exhibit deleterious properties. Using pulse radiolysis, this study determined that the bimolecular rate constants of scavenging cation radicals of retinoids by taurine are smaller than 2 × 107 M-1s-1 whereas lutein scavenges cation radicals of all three retinoids with the bimolecular rate constants approach the diffusion-controlled limits, while zeaxanthin is only 1.4-1.6-fold less effective. Despite that lutein exhibits greater scavenging rate constants of retinoid cation radicals than other antioxidants, the greater concentrations of ascorbate in the retina suggest that ascorbate may be the main protectant of all visual cycle retinoids from oxidative degradation, while α-tocopherol may play a substantial role in the protection of retinaldehyde but is relatively inefficient in the protection of retinol or retinyl palmitate. While the protection of retinoids by lutein and zeaxanthin appears inefficient in the retinal periphery, it can be quite substantial in the macula. Although the determined rate constants of scavenging the cation radicals of retinol and retinaldehyde by dopa-melanin are relatively small, the high concentration of melanin in the RPE melanosomes suggests they can be scavenged if they are in proximity to melanin-containing pigment granules.

Isolation and Characterization of a Yellow Xanthophyll Pigment-Producing Marine Bacterium, Erythrobacter sp. SDW2 Strain, in Coastal Seawater.

Xanthophylls, a yellow pigment belonging to the carotenoid family, have attracted much attention for industrial applications due to their versatile nature. We report the isolation of a homo xanthophyll pigment-producing marine bacterium, identified as the Erythrobacter sp. SDW2 strain, from coastal seawater. The isolated Erythrobacter sp. SDW2 strain can produce 263 ± 12.9 mg/L (89.7 ± 5.4 mg/g dry cell weight) of yellow xanthophyll pigment from 5 g/L of glucose. Moreover, the xanthophyll pigment produced by the SDW2 strain exhibits remarkable antioxidative activities, confirmed by the DPPH (73.4 ± 1.4%) and ABTS (84.9 ± 0.7%) assays. These results suggest that the yellow xanthophyll pigment-producing Erythrobacter sp. SDW2 strain could be a promising industrial microorganism for producing marine-derived bioactive compounds with potential for foods, cosmetics, and pharmaceuticals.

Pigment Composition of Nine Brown Algae from the Iberian Northwestern Coastline: Influence of the Extraction Solvent.

Brown algae are ubiquitously distributed in the NW coastline of the Iberian Peninsula, where they stand as an underexploited resource. In this study, five solvents were applied to the extraction of pigments from nine brown algae, followed by their determination and quantification by HPLC-DAD. A total of 13 compounds were detected: Six were identified as chlorophylls, six were classified as xanthophylls, and one compound was reported as a carotene. Fucoxanthin was reported in all extracts, which is the most prominent pigment of these algae. Among them, L. saccharina and U. pinnatifida present the highest concentration of fucoxanthin (4.5-4.7 mg∙g-1 dry weight). Ethanol and acetone were revealed as the most efficient solvents for the extraction of pigments, showing a maximal value of 11.9 mg of total pigments per gram of dry alga obtained from the ethanolic extracts of H. elongata, followed by the acetonic extracts of L. ochroleuca. Indeed, ethanol was also revealed as the most efficient solvent according to its high extraction yield along all species evaluated. Our results supply insights into the pigment composition of brown algae, opening new perspectives on their commercial exploitation by food, pharmaceutical, and cosmeceutical industries.

The Identification and Quantitative Analysis of Unusual Keto-Carotenoids in Ripe Fruits of Maclura tricuspidate and Its Potential as a Valuable Source of Cryptocapsin.

Ripe fruits of Maclura tricuspidata (MT) are used as food material and a natural colorant in Korea. Although MT fruits have a deep red color due to carotenoid-like pigments, their chemical nature has not been explored in detail so far. The present study aimed at elucidating the chemical structures and composition of carotenoids in MT fruits and changes at different maturity stages. Two carotenoids from saponified MT fruit extract were isolated using repeated silica gel column chromatography. Based on interpretations of spectroscopic data, these compounds were determined as keto-carotenoids, i.e., capsanthin (3,3'-dihydroxy-ß,κ-caroten-6'-one) and cryptocapsin (3'-hydroxy-ß,κ-caroten-6'-one), and the contents of individual carotenoids were quantified with HPLC based on calibration curves obtained from authentic standards. The contents of capsanthin and cryptocapsin in the sample of saponified MT fruits were 57.65 ± 1.97 µg/g and 171.66 ± 4.85 µg/g as dry weight base (dw). The majority of these keto-carotenoids in the MT fruits were present in esterified forms with lauric, myristic or palmitic acid rather than in their free forms. The results also showed that esterification of these compounds occurred starting from early stage (yellow-brownish stage) of maturation. Considering the high cryptocapsin content, MT fruits can be applied as a potentially valuable source of cryptocapsin for food and medicinal application as well as a source of provitamin A.

How dry is dry? Molecular mobility in relation to thallus water content in a lichen.

Lichens can withstand extreme desiccation to water contents of ≤ 0.1 g H2O g-1 DW, and in the desiccated state are among the most extremotolerant organisms known. Desiccation-tolerant life-forms such as seeds, mosses and lichens survive 'vitrification', that is the transition of their cytoplasm to a 'glassy' state, which causes metabolism to cease. However, our understanding of the mechanisms of desiccation tolerance is hindered by poor knowledge of what reactions occur in the desiccated state. Using Flavoparmelia caperata as a model lichen, we determined at what water contents vitrification occurred upon desiccation. Molecular mobility was assessed by dynamic mechanical thermal analysis, and the de- and re-epoxidation of the xanthophyll cycle pigments (measured by HPLC) was used as a proxy to assess enzyme activity. At 20 °C vitrification occurred between 0.12-0.08 g H2O g-1 DW and enzymes were active in a 'rubbery' state (0.17 g H2O g-1 DW) but not in a glassy state (0.03 g H2O g-1 DW). Therefore, desiccated tissues may appear to be 'dry' in the conventional sense, but subtle differences in water content will have substantial consequences on the types of (bio)chemical reactions that can occur, with downstream effects on longevity in the desiccated state.

Enhancement of Xanthophyll Synthesis in Porphyra/Pyropia Species (Rhodophyta, Bangiales) by Controlled Abiotic Factors: A Systematic Review and Meta-Analysis.

Red alga species belonging to the Porphyra and Pyropia genera (commonly known as Nori), which are widely consumed and commercialized due to their high nutritional value. These species have a carotenoid profile dominated by xanthophylls, mostly lutein and zeaxanthin, which have relevant benefits for human health. The effects of different abiotic factors on xanthophyll synthesis in these species have been scarcely studied, despite their health benefits. The objectives of this study were (i) to identify the abiotic factors that enhance the synthesis of xanthophylls in Porphyra/Pyropia species by conducting a systematic review and meta-analysis of the xanthophyll content found in the literature, and (ii) to recommend a culture method that would allow a significant accumulation of these compounds in the biomass of these species. The results show that salinity significantly affected the content of total carotenoids and led to higher values under hypersaline conditions (70,247.91 µg/g dm at 55 psu). For lutein and zeaxanthin, the wavelength treatment caused significant differences between the basal and maximum content (4.16-23.47 µg/g dm). Additionally, in Pyropia spp., the total carotenoids were considerably higher than in Porphyra spp.; however, the lutein and zeaxanthin contents were lower. We discuss the specific conditions for each treatment and the relation to the ecological distribution of these species.

Xanthophylls from the Sea: Algae as Source of Bioactive Carotenoids.

Algae are considered pigment-producing organisms. The function of these compounds in algae is to carry out photosynthesis. They have a great variety of pigments, which can be classified into three large groups: chlorophylls, carotenoids, and phycobilins. Within the carotenoids are xanthophylls. Xanthophylls (fucoxanthin, astaxanthin, lutein, zeaxanthin, and ß-cryptoxanthin) are a type of carotenoids with anti-tumor and anti-inflammatory activities, due to their chemical structure rich in double bonds that provides them with antioxidant properties. In this context, xanthophylls can protect other molecules from oxidative stress by turning off singlet oxygen damage through various mechanisms. Based on clinical studies, this review shows the available information concerning the bioactivity and biological effects of the main xanthophylls present in algae. In addition, the algae with the highest production rate of the different compounds of interest were studied. It was observed that fucoxanthin is obtained mainly from the brown seaweeds Laminaria japonica, Undaria pinnatifida, Hizikia fusiformis, Sargassum spp., and Fucus spp. The main sources of astaxanthin are the microalgae Haematococcus pluvialis, Chlorella zofingiensis, and Chlorococcum sp. Lutein and zeaxanthin are mainly found in algal species such as Scenedesmus spp., Chlorella spp., Rhodophyta spp., or Spirulina spp. However, the extraction and purification processes of xanthophylls from algae need to be standardized to facilitate their commercialization. Finally, we assessed factors that determine the bioavailability and bioaccesibility of these molecules. We also suggested techniques that increase xanthophyll's bioavailability.

A simple and fast experimental protocol for the extraction of xanthophylls from microalga Chlorella luteoviridis.

This study aimed to optimize the key parameters of extraction methods and to increase the recovery yields of intact xanthophylls (violaxanthin, zeaxanthin, astaxanthin) from microalgae (Chlorella luteoviridis). An effective, simple, and fast extraction protocol is described. It consists of a grinding pretreatment followed by a microwave-assisted extraction, using ethanol 90% as an environmentally preferable extraction solvent. Xanthopylls were quantified using high performance liquid chromatography. Irradiation time of 6 s only resulted in the extraction of violaxanthin (4.479 ± 0.009 mg/g), astaxanthin (4.154 ± 0.013 mg/g), and zeaxanthin (4.776 ± 0.120 mg/g). The described protocol seems to be the fastest extraction method of xantophylls compared to the literature and could be an advantage for industrial scale, while saving time and energy.

Astaxanthin for the Food Industry.

Xanthophyll astaxanthin, which is commonly used in aquaculture, is one of the most expensive and important industrial pigments. It is responsible for the pink and red color of salmonid meat and shrimp. Due to having the strongest anti-oxidative properties among carotenoids and other health benefits, natural astaxanthin is used in nutraceuticals and cosmetics, and in some countries, occasionally, to fortify foods and beverages. Its use in food technology is limited due to the unknown effects of long-term consumption of synthetic astaxanthin on human health as well as few sources and the high cost of natural astaxanthin. The article characterizes the structure, health-promoting properties, commercial sources and industrial use of astaxanthin. It presents the possibilities and limitations of the use of astaxanthin in food technology, considering its costs and food safety. It also presents the possibilities of stabilizing astaxanthin and improving its bioavailability by means of micro- and nanoencapsulation.

Metabolomic Insights into Marine Phytoplankton Diversity.

The democratization of sequencing technologies fostered a leap in our knowledge of the diversity of marine phytoplanktonic microalgae, revealing many previously unknown species and lineages. The evolutionary history of the diversification of microalgae can be inferred from the analysis of their genome sequences. However, the link between the DNA sequence and the associated phenotype is notoriously difficult to assess, all the more so for marine phytoplanktonic microalgae for which the lab culture and, thus, biological experimentation is very tedious. Here, we explore the potential of a high-throughput untargeted metabolomic approach to explore the phenotypic-genotypic gap in 12 marine microalgae encompassing 1.2 billion years of evolution. We identified species- and lineage-specific metabolites. We also provide evidence of a very good correlation between the molecular divergence, inferred from the DNA sequences, and the metabolomic divergence, inferred from the complete metabolomic profiles. These results provide novel insights into the potential of chemotaxonomy in marine phytoplankton and support the hypothesis of a metabolomic clock, suggesting that DNA and metabolomic profiles co-evolve.

Disruption of a horizontally transferred phytoene desaturase abolishes carotenoid accumulation and diapause in Tetranychus urticae.

Carotenoids underlie many of the vibrant yellow, orange, and red colors in animals, and are involved in processes ranging from vision to protection from stresses. Most animals acquire carotenoids from their diets because de novo synthesis of carotenoids is primarily limited to plants and some bacteria and fungi. Recently, sequencing projects in aphids and adelgids, spider mites, and gall midges identified genes with homology to fungal sequences encoding de novo carotenoid biosynthetic proteins like phytoene desaturase. The finding of horizontal gene transfers of carotenoid biosynthetic genes to three arthropod lineages was unprecedented; however, the relevance of the transfers for the arthropods that acquired them has remained largely speculative, which is especially true for spider mites that feed on plant cell contents, a known source of carotenoids. Pigmentation in spider mites results solely from carotenoids. Using a combination of genetic approaches, we show that mutations in a single horizontally transferred phytoene desaturase result in complete albinism in the two-spotted spider mite, Tetranychus urticae, as well as in the citrus red mite, Panonychus citri Further, we show that phytoene desaturase activity is essential for photoperiodic induction of diapause in an overwintering strain of T. urticae, consistent with a role for this enzyme in provisioning provitamin A carotenoids required for light perception. Carotenoid biosynthetic genes of fungal origin have therefore enabled some mites to forgo dietary carotenoids, with endogenous synthesis underlying their intense pigmentation and ability to enter diapause, a key to the global distribution of major spider mite pests of agriculture.

Kaolin Reduces ABA Biosynthesis Through the Inhibition of Neoxanthin Synthesis in Grapevines Under Water Deficit.

In many viticulture regions, multiple summer stresses are occurring with increased frequency and severity because of warming trends. Kaolin-based particle film technology is a technique that can mitigate the negative effects of intense and/or prolonged drought on grapevine physiology. Although a primary mechanism of action of kaolin is the increase of radiation reflection, some indirect effects are the protection of canopy functionality and faster stress recovery by abscisic acid (ABA) regulation. The physiological mechanism underlying the kaolin regulation of canopy functionality under water deficit is still poorly understood. In a dry-down experiment carried out on grapevines, at the peak of stress and when control vines zeroed whole-canopy net CO2 exchange rates/leaf area (NCER/LA), kaolin-treated vines maintained positive NCER/LA (~2 µmol m-2 s-1) and canopy transpiration (E) (0.57 µmol m-2 s-1). Kaolin-coated leaves had a higher violaxanthin (Vx) + antheraxanthin (Ax) + zeaxanthin (Zx) pool and a significantly lower neoxanthin (Nx) content (VAZ) when water deficit became severe. At the peak of water shortage, leaf ABA suddenly increased by 4-fold in control vines, whereas in kaolin-coated leaves the variation of ABA content was limited. Overall, kaolin prevented the biosynthesis of ABA by avoiding the deviation of the VAZ epoxidation/de-epoxidation cycle into the ABA precursor (i.e., Nx) biosynthetic direction. The preservation of the active VAZ cycle and transpiration led to an improved dissipation of exceeding electrons, explaining the higher resilience of canopy functionality expressed by canopies sprayed by kaolin. These results point out the interaction of kaolin with the regulation of the VAZ cycle and the active mechanism of stomatal conductance regulation.