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The involvements of iron metabolism, lipid peroxidation, and oxidative stress in Alzheimer's disease (AD) development have recently received a lot of attention. We also observe that these pathogenic occurrences play a key role in regulating ferroptosis, a unique regulatory cell death that is iron-dependent, oxidative, and non-apoptotic. Iron is a crucial component that makes up a subunit of the oxidase responsible for lipid peroxidation. A family of non-heme iron enzymes known as lipoxygenases (LOXs) can cause ferroptosis by oxidising polyunsaturated fatty acids in cellular membranes (PUFAs). Toxic lipid hydroperoxides are produced in large part by the iron in LOX active sites. Deferoxamine and deferiprone, two iron chelators, could also treat ferroptosis by eliminating the crucial catalytic iron from LOXs. Phospholipids containing polyunsaturated fatty acids are the main substrates of lipid peroxidation in ferroptosis, which is favourably controlled by enzymes like ACSL4, LPCAT3, ALOXs, or POR. Selective stimulation of autophagic degradation pathways leads to an increase in iron accumulation and lipid peroxidation, which promotes ferroptosis. We highlighted recent advancements in our understanding of ferroptosis signaling routes in this study. One form of regulated necrotic cell death known as ferroptosis has been linked to a number of diseases, including cancer, neurological disorders, and ischemia/reperfusion injury. Cerebrospinal fluid (CSF) ferritin may be a good indicator of the amount of iron in the brain because it is the main protein that stores iron. [ABSTRACT FROM AUTHOR]

To investigate in detail the volatilomes of various Brassicaceae species, landraces, and accessions, and to extract specific volatile markers, volatile aroma compounds were isolated from plant samples by headspace solid-phase microextraction and analyzed by gas chromatography/mass spectrometry (HS-SPME-GC/MS). The data obtained were subjected to uni- and multivariate statistical analysis. In general, two cabbage (Brassica oleracea L. var. capitata) landraces emitted the lowest amounts of volatiles generated in the lipoxygenase (LOX) pathway. Wild species Brassica incana Ten. and Brassica mollis Vis. were characterized by relatively high trans-2-hexenal/cis-3-hexen-1-ol ratio in relation to other investigated samples. A Savoy cabbage (Brassica oleracea L. var. sabauda) cultivar and three kale (Brassica oleracea L. var. acephala) accessions exhibited particular similarities in the composition of LOX volatiles, while the LOX volatilome fraction of B. incana and B. mollis partially coincided with that of another wild species, Diplotaxis tenuifolia L. Regarding volatiles formed in the glucosinolate (GSL) pathway, Savoy cabbage and wild species B. incana, B. mollis, and D. tenuifolia showed more intense emission of isothiocyanates than cabbage and kale. Diplotaxis tenuifolia showed a rather limited production of nitriles. The results of this study contribute to the general knowledge about volatile composition from various Brassicaceae species, which could be exploited for their better valorization. Future studies should focus on the influence of various environmental, cultivation, and post-harvest factors to obtain data with a higher level of applicability in practice. [ABSTRACT FROM AUTHOR]

The bamboo powderpost beetle, Dinoderus minutus (Fabricius) (Coleoptera: Bostrichidae), is the major post‐harvest pest of several bamboo species worldwide. Conspecific adults colonize injured bamboo stems, primarily those with low moisture content. Here, the volatiles from dry cut stems of Bambusa vulgaris Schrad. ex J.C. Wendl (Poaceae) were identified and field‐tested for attraction of adults of D. minutus. Analyses of headspace volatile extracts from these stems revealed 22 compounds, of which hexanal was the most abundant, followed by heptanal, octanal, nonanal, decanal, and 2‐pentylfuran. Together, these six compounds comprised >94% of the total abundance of airborne volatiles from dry cut bamboo stems. The biological activity of these compounds was tested in three consecutive field‐trapping trials in Brazil. Broadly speaking, the binary blend of hexanal and decanal was the optimal attractant for both male and female D. minutus adults, whereas hexanal alone was not attractive and the presence of heptanal, octanal, nonanal, and 2‐pentylfuran in some tested blends proved to be redundant or disruptive in attracting conspecific beetles. Traps baited with hexanal and decanal could be used for surveillance and monitoring of D. minutus at countries' points‐of‐entry and for integrated pest management (IPM) at storage facilities of post‐harvest bamboo stems and related products. [ABSTRACT FROM AUTHOR]

BACKGROUND There is increasing consumer demand for olive oil to be traceable. However, genotype, environmental factors, and stage of maturity, all affect the flavor and composition of both the olives and olive oil. Few studies have included all three variables. Key metabolites include lipids, phenolics, and a wide range of volatile organic compounds (VOCs), which provide the olives and oil with their characteristic flavor. Here we aim to identify markers that are able to discriminate between cultivars, that can identify growth location, and can discriminate stages of fruit maturity. 'Nocellara messinese' and 'Carolea' olive fruits were grown at three locations differing in altitude in Calabria, Italy, and harvested at three stages of maturity. Oil was analyzed from the two most mature stages. RESULTS: Nine and 20 characters discriminated all fruit and oil samples respectively, and relative abundance of two fatty acids distinguished all oils. Whole VOC profiles discriminated among the least mature olives, and oil VOC profiles discriminated location and cultivar at both stages. Three VOCs putatively identified as hexanal, methyl acetate, and 3‐hexen‐1‐ol differentiated all samples of oils from the most mature fruit stage. CONCLUSION: The results confirm that interactions of location, cultivar and fruit maturity stage are critical for the overall pattern of aroma compounds, and identify potential markers of commercial relevance. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

To investigate in detail the volatilomes of various Brassicaceae species, landraces, and accessions, and to extract specific volatile markers, volatile aroma compounds were isolated from plant samples by headspace solid-phase microextraction and analyzed by gas chromatography/mass spectrometry (HS-SPME-GC/MS). The data obtained were subjected to uni- and multivariate statistical analysis. In general, two cabbage (Brassica oleracea L. var. capitata) landraces emitted the lowest amounts of volatiles generated in the lipoxygenase (LOX) pathway. Wild species Brassica incana Ten. and Brassica mollis Vis. were characterized by relatively high trans-2-hexenal/cis-3-hexen-1-ol ratio in relation to other investigated samples. A Savoy cabbage (Brassica oleracea L. var. sabauda) cultivar and three kale (Brassica oleracea L. var. acephala) accessions exhibited particular similarities in the composition of LOX volatiles, while the LOX volatilome fraction of B. incana and B. mollis partially coincided with that of another wild species, Diplotaxis tenuifolia L. Regarding volatiles formed in the glucosinolate (GSL) pathway, Savoy cabbage and wild species B. incana, B. mollis, and D. tenuifolia showed more intense emission of isothiocyanates than cabbage and kale. Diplotaxis tenuifolia showed a rather limited production of nitriles. The results of this study contribute to the general knowledge about volatile composition from various Brassicaceae species, which could be exploited for their better valorization. Future studies should focus on the influence of various environmental, cultivation, and post-harvest factors to obtain data with a higher level of applicability in practice.

The effects of 1.0 μL/L 1-methylcyclopropene (1-MCP) treatment on aroma quality and ester-biosynthesis-related gene expression of ‘Jinyan’ kiwifruit during room storage were examined, aiming to provide a theoretical basis and technical reference for the postharvest storage of kiwifruit. The results demonstrate that 1-MCP treatment conspicuously inhibited respiration rate, delayed a decrease in fruit firmness and increased soluble solid content (SSC) in ‘Jinyan’ kiwifruit. Compared to the control, the relative content of aroma components markedly changed in 1-MCP treatment kiwifruit during fruit ripening. The characteristic aroma of ‘Jinyan’ kiwifruit included ethyl butanoate, methyl butanoate, E-2-hexanal and hexenal, and 1-MCP treatment significantly reduced the ester content in kiwifruit. During the entire shelf life, the expression levels of AcLOX1, AcLOX5, AcLOX6, AcHPL and AcAAT were significantly inhibited in 1-MCP-treated fruit. However, the transcript level of AcADH was not suppressed by 1-MCP. The lower content of ester volatiles maybe ascribed to the suppression of AcLOXs, AcHPL and AcAAT. [ABSTRACT FROM AUTHOR]

The patterns of volatile organic compounds (VOCs) emission and the expression of genes associated with the lipoxygenase (LOX) pathway have been studied in harvested peach fruit of two cultivars ('Flaminia', FL, and 'Red Haven', RH) during and after cold storage. Two temperature storage conditions have been applied for two weeks: 0.5 and 5.5°C, the latter recognized to be an inducer factor of chilling injury (CI) of the flesh. Fruit were also monitored during 3 days of shelf-life (SL) at room temperature after removing from the cold storage. A different behaviour between cultivars has been observed in terms of internal browning (more evident in FL after 2 weeks) and extractable juice (already reduced in RH at the end of 1 week of storage at 5.5°C). Although some common responses have been observed (e.g. a general increase of 2-hexenal and 2-hexenal-E at the end of both cold storage conditions), LOX pathway-associated volatiles (aldehydes, alcohols, esters) showed different trends in relation to the genotype and the applied stress, with apparently no specific correlations with the incidence of CI. The expression level of five LOX pathway-associated genes (PpLOX1, PpLOX4, PpHPL1, PpADH1, PpAAT1) have been analysed and the results point out that a genotype-dependent behaviour is present, but specific responses (up-regulation of PpLOX1 and PpAAT1 during SL) appear to be present in both cultivars. In addition, the expression of two C-repeat-binding factors (PpCBF1 and PpCBF6), recognized to be involved in the responses of plant tissues to low temperature stress, showed marked changes in relation to the applied temperature, suggesting that these genes might play a regulatory role in the overall metabolism of cold stored peaches.

The patterns of volatile organic compounds (VOCs) emission and the expression of genes associated with the lipoxygenase (LOX) pathway have been studied in harvested peach fruit of two cultivars ('Flaminia', FL, and 'Red Haven', RH) during and after cold storage. Two temperature storage conditions have been applied for two weeks: 0.5 and 5.5°C, the latter recognized to be an inducer factor of chilling injury (CI) of the flesh. Fruit were also monitored during 3 days of shelflife (SL) at room temperature after removing from the cold storage. A different behaviour between cultivars has been observed in terms of internal browning (more evident in FL after 2 weeks) and extractable juice (already reduced in RH at the end of 1 week of storage at 5.5°C). Although some common responses have been observed (e.g. a general increase of 2hexenal and 2hexenalE at the end of both cold storage conditions), LOX pathwayassociated volatiles (aldehydes, alcohols, esters) showed different trends in relation to the genotype and the applied stress, with apparently no specific correlations with the incidence of CI. The expression level of five LOX pathwayassociated genes (PpLOX1, PpLOX4, PpHPL1, PpADH1, PpAAT1) have been analysed and the results point out that a genotypedependent behaviour is present, but specific responses (upregulation of PpLOX1 and PpAAT1 during SL) appear to be present in both cultivars. In addition, the expression of two C-repeatbinding factors (PpCBF1 and PpCBF6), recognized to be involved in the responses of plant tissues to low temperature stress, showed marked changes in relation to the applied temperature, suggesting that these genes might play a regulatory role in the overall metabolism of cold stored peaches. [ABSTRACT FROM AUTHOR]

The metabolism of polyunsaturated fatty acids through the lipoxygenase-catalyzed step and subsequent reactions is referred to as the lipoxygenase (LOX) pathway. The components of this system, such as jasmonates, are involved in growth, development and defense reactions of plants. In this report, we focus on dynamics of expression of different LOX pathway genes and activities of target enzymes with three abiotic stress factors: darkness, salinity and herbicide toxicity. To obtain a more complete picture, the expression profiles of marker genes for salicylic acid, abscisic acid, ethylene, auxin and gibberellin-dependent signaling systems under the same stresses were also analyzed. The gene expression in Solanum tuberosum plants was analyzed using qRT-PCR, and we found that the LOX-cascade-related genes responded to darkness, salinity and herbicide toxicity in different ways. We detected activation of a number of 9-LOX pathway genes; however, in contrast to studies associated with biotic stress (infection), the 9-divinyl ether synthase branch of the LOX cascade was inhibited under all three stresses. GC-MS analysis of the oxylipin profiles also showed the main activity of the 9-LOX-cascade-related enzymes after treatment with herbicide and darkness.

Plant (or phyto-) oxylipins (POs) are produced under a wide range of stress conditions and although they are well known to activate stress-related signalling pathways, the nonsignalling roles of POs are poorly understood. We describe oxylipins as direct biocidal agents and propose that structure–function relationships play here a pivotal role. Based on their chemical configuration, POs, such as reactive oxygen and electrophile species, activate defence-related gene expression. We also propose that their ability to interact with pathogen membranes is important, but still misunderstood, and that they are involved in cross-kingdom communication. Taken as a whole, the current literature suggests that POs have a high potential as biocontrol agents. However, the mechanisms underlying these multifaceted compounds remain largely unknown. Many studies have shown that specific oxylipin signatures are shaped during (a)biotic stresses. It is generally accepted that divinyl-, keto-, and hydroxy-fatty acids and fatty acid hydroperoxides exhibit strong direct antimicrobial activities, whereas the roles of jasmonic acid and some volatile aldehydes seem to be related to signalling activities only. Oxylipins' chemical structures are related to their biological activities. Current studies show that the lipid composition of the plasma membrane has important roles in the interaction of plant oxylipins with plant cells. It is becoming clear that many organisms use the oxylipin pathways as a common process for interkingdom communication [ABSTRACT FROM AUTHOR]

Natural vegetation is predicted to suffer from extreme heat events as a result of global warming. In this study, we focused on the immediate response to heat stress. Photosynthesis and volatile emissions were measured in the leaves of tobacco (Nicotiana tabacum cv. Wisconsin 38) after exposure to heat shock treatments between 46 °C and 55 °C. Exposure to 46 °C decreased photosynthetic carbon assimilation rates (A) by >3-fold. Complete inhibition of A was observed at 49 °C, together with a simultaneous decrease in the maximum quantum efficiency of PSII, measured as the F v/ F m ratio. A large increase in volatile emissions was observed at 52 °C. Heat stress resulted in only minor effects on the emission of monoterpenes, but volatiles associated with membrane damage such as propanal and (E)-2-hexenal+(Z)-3-hexenol were greatly increased. Heat induced changes in the levels of methanol and 2-ethylfuran that are indicative of modification of cell walls. In addition, the oxidation of metabolites in the volatile profiles was strongly enhanced, suggesting the acceleration of oxidative processes at high temperatures that are beyond the thermal tolerance limit. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• A novel within-leaf-chamber cutter and an advanced volatile sampling methodology are developed. • The novel methodology allows conduction of real-time leaf wounding experiments. • The use of the novel methodology demonstrated very rapid induction and unprecedently high emission rates of stress volatiles and stored monoterpenes. • The analysis reported here suggests that past studies have underestimated the rate of elicitation and maximum emission rates of wound-dependent volatiles. Wounding is a key plant stress that results in a rapid, within seconds to a few minutes, release of ubiquitous stress volatiles and stored volatiles in species with storage structures. Understanding the timing and extent of wound-dependent volatile elicitation is needed to gain an insight into different emission controls, but real-time monitoring of plant emissions through wounding treatments has been hampered by the need to stop the measurements to perform the wounding, slow stabilization of gas flows upon chamber closure and smearing out the signal by large chambers and long sampling lines. We developed a novel leaf cutter that allows to rapidly perform highly precise leaf cuts within the leaf chamber. The cutter was fitted to the standard Walz GFS-3000 portable gas-exchange system leaf chamber and chamber exhaust air for analysis with a proton transfer reaction time-of-flight mass-spectrometer (PTR-TOF-MS) was taken right at the leaf chamber outlet. Wounding experiments in four species of contrasting leaf structure demonstrated significant species differences in timing, extent and blend of emitted volatiles, and showed unprecedently high emission rates of several stress volatiles and stored monoterpenes. In light of the rapid rise of release of de novo synthesized and stored volatiles, the results of this study suggest that past studies have underestimated the rate of elicitation and maximum emission rates of wound-dependent volatiles. [ABSTRACT FROM AUTHOR]

The crystal structure of 13R-manganese lipoxygenase (MnLOX) of Gaeumannomyces graminis (Gg) in complex with zonadhesin of Pichia pastoris was solved by molecular replacement. Zonadhesin contains β-strands in two subdomains. A comparison of Gg-MnLOX with the 9S-MnLOX of Magnaporthe oryzae (Mo) shows that the protein fold and the geometry of the metal ligands are conserved. The U-shaped active sites differ mainly due to hydrophobic residues of the substrate channel. The volumes and two hydrophobic side pockets near the catalytic base may sanction oxygenation at C-13 and C-9, respectively. Gly-332 of Gg-MnLOX is positioned in the substrate channel between the entrance and the metal center. Replacements with larger residues could restrict oxygen and substrate to reach the active site. C18 fatty acids are likely positioned with C-11 between Mn2+OH2 and Leu-336 for hydrogen abstraction and with one side of the 12Z double bond shielded by Phe-337 to prevent antarafacial oxygenation at C-13 and C-11. Phe-347 is positioned at the end of the substrate channel and replacement with smaller residues can position C18 fatty acids for oxygenation at C-9. Gg-MnLOX does not catalyze the sequential lipoxygenation of n-3 fatty acids in contrast to Mo-MnLOX, which illustrates the different configurations of their substrate channels.

A head space-solid phase microextraction-gas chromatography-mass spectrometery (HS-SPME-GC-MS) method for the simultaneous analysis of pentene dimers from lipoxygenase (LOX) pathway, monoterpenes, and sesquiterpenes in extra virgin olive oil (EVOO) was proposed. A Doehlert design was performed; the conditions of the HS-SPME preconcentration step (extraction temperature, extraction time, sample amount, and desorption time) were optimized by response surface methodology, allowing defining the method operable design region. A quantitative method was set up using the multiple internal standard normalization approach: four internal standards were used, and the most suitable one was selected for area normalization of each external standard. The quantitative method was successfully validated and applied to a series of monocultivar EVOOs. This is the first paper in which a quantitative method using commercial standards has been proposed for the analysis of an important class of molecules of EVOO such as pentene dimers. The optimized method is suitable for routine analysis aimed at characterizing high quality EVOOs.

Abstract Diatoms are eukaryotic microalgae that play a pivotal role in biological and geochemical marine cycles. These microorganisms are at the basis of the trophic chain and their lipids are essential components (e.g. eicosapentaenoic acid, EPA) of aquatic food webs. Galactolipids are the primary lipid components of plastid membranes and form the largest lipid family of diatoms. As source of polyunsaturated fatty acids (PUFAs), these compounds are also involved in the synthesis of lipoxygenase (LOX) products such as non-volatile oxylipins and polyunsaturated aldehydes. Here, we report the first identification of two genes, namely PmLAH1 and PaLAH1 , coding for lipolytic enzymes in two diatoms of the genus Pseudo-nitzschia. Functional and modeling studies evidence a patatin-like domain endowed with galactolipase and phospholipase activity at the C-terminus of both proteins. Homologues of Pseudo-nitzschia LAH1 genes were retrieved in other diatom species so far sequenced in agreement with conservation of the functional role of these proteins within the lineage. Highlights • Galactolipids are key components of chloroplast membranes and major lipid class in marine diatoms under natural growth conditions. • By targeting glycolipids and phospholipids, different patatin-like proteins relay a growing number of important biological functions in the development and pathology of photosynthetic organisms. • LAH1 of P. arenysensis and P. multistriata contain the first patatin-like sequence identified in diatoms. The putative genes showed good sequence conservation in the patatin-like PLA (GxSxG) motif and catalytic dyad, as well as high similarity in the domain region (in the protein secondary structure level) with the patatin from Solanum cardiophyllum. • Homologous LAH1 genes are also found in the genomes or transcriptomes of any other diatom so far sequenced. The phylogenetic analysis showed that PmLAH and PaLAH formed a monophyletic group with other secondary red endosymbionts. • In analogy with plants, LAH1 is involved in the biosynthesis of oxylipins and may control the physiological role of these chemical mediators in diatom cells. Analogies with other microalgae and overexpression of LAH1 in P. tricornutum (XP_002180454.1) under N-starvation support also a possible role of this class of enzymes in galactolipid metabolism and lipid remodelling of diatoms. [ABSTRACT FROM AUTHOR]

Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract: A quantitative method, based on SPME GC‐MS, for the quantification of volatile compounds derived from lipoxygenase pathway, considered the most important for the aroma of high‐quality olive oil, was developed. The method was used to study the variation within the extra virgin olive oils from 67 cultivars of the Tuscan olive germplasm conserved at “Santa Paolina” experimental farm (Follonica, Italy). A great variability was observed among the 67 cultivars both for the total amount of volatile compounds and for the different ratios between the groups of volatile compounds from common precursors. The aim was to obtain basic information on the characteristics and the quality of the oils obtainable from nonwidely cultivated olive varieties. These data can support the reintroduction in the production chain of old autochthonous varieties and for exploitation in breeding programs as a source of positive characters to transmit to the progeny. [ABSTRACT FROM AUTHOR]

Plant oxylipins form a constantly growing group of signaling molecules that comprise oxygenated fatty acids and metabolites derived therefrom. In the last decade, the understanding of biosynthesis, metabolism, and action of oxylipins, especially jasmonates, has dramatically improved. Additional mechanistic insights into the action of enzymes and insights into signaling pathways have been deepened for jasmonates. For other oxylipins, such as the hydroxy fatty acids, individual signaling properties and cross talk between different oxylipins or even with additional phytohormones have recently been described. This review summarizes recent understanding of the biosynthesis, regulation, and function of oxylipins. [ABSTRACT FROM AUTHOR]

The volatile profile of crushed rocket leaves ( Eruca sativa and Diplotaxis tenuifolia ) was investigated by applying Headspace Solid-Phase MicroExtraction (HS-SPME), combined with GC–MS, to an aqueous extract obtained by homogenization of rocket leaves, and stabilized by addition of CaCl 2 . A detailed picture of volatile products of the lipoxygenase pathway (mainly C6-aldehydes) and of glucosinolate hydrolysis (mainly isothiocyanates), and their dynamics of formation after tissue disruption was given. Odor-active compounds of leaves were characterized by GC-Olfactometry (GC-O) and Aroma Extract Dilution Analysis (AEDA): volatile isolates obtained by HS-SPME from an aqueous extract and by Stir-Bar Sorptive Extraction (SBSE) from an ethanolic extract were analyzed. The most potent odor-active compounds fully or tentatively identified were ( Z )- and ( E )-3-hexenal, ( Z )-1,5-octadien-3-one, responsible for green olfactory notes, along with 4-mercaptobutyl and 4-(methylthio)butyl isothiocyanate, associated with typical rocket and radish aroma. Relatively high odor potency was observed for 1-octen-3-one, ( E )-2-octenal and 1-penten-3-one. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recent studies have highlighted the biological and physiological effects of pre-harvest ultraviolet (UV)-C treatment on growing plants. However, little is known about the involvement of volatile organic compounds (VOCs) and their response to this treatment. In this study, strawberry plants were exposed to three different doses of UV-C radiation for seven weeks (a low dose: 9.6 kJ m −2 ; a medium dose: 15 kJ m −2 ; and a high-dose: 29.4 kJ m −2 ). Changes in VOC profiles were investigated and an attempt was made to identify factors that may be involved in the regulation of these alterations. Principle compounds analysis revealed that VOC profiles of UV-C treated samples were significantly altered with 26 VOCs being the major contributors to segregation. Among them, 18 fatty acid–derived VOCs accumulated in plants that received high and medium dose of UV-C treatments with higher lipoxygenase and alcohol dehydrogenase activities. In treated samples, the activity of the antioxidant enzymes catalase and peroxidase was inhibited, resulting in a reduced antioxidant capacity and higher lipid peroxidation. Simultaneously, jasmonic acid level was 74% higher in the high-dose group while abscisic acid content was more than 12% lower in both the medium and high-dose UV-C treated samples. These results indicated that pre-harvest UV-C treatment stimulated the biosynthesis of fatty acid–derived VOCs in strawberry leaf tissue by upregulating the activity of enzymes of the LOX biosynthetic pathway and downregulating antioxidant enzyme activities. It is further suggested that the mechanisms underlying fatty acid-derived VOCs biosynthesis in UV-C treated strawberry leaves are associated with UV-C-induced changes in phytohormone profiles. [ABSTRACT FROM AUTHOR]

Aroma is an important quality criterion for extra virgin olive oil. The goal of this study was to determine C and C volatile compounds in different Turkish olive oils. Two factors namely (1) olive cultivar including Ayvalik, Memecik, and Topakasi, and (2) harvest time (ripening degree) were studied. Both factors significantly affected the volatile profiles of the studied oils. Headspace solid phase micro-extraction with GC/MS was used to detect volatiles in different olive oils. The detected volatile compounds included up to 11 compounds (4 from C, and 7 from C). Hexanal and ( E)-2-hexanal were predominated as the major volatiles in Ayvalik, and Memecik oils, while pentanal, and hexanal were predominated in Topakasi oil. Topakasi oil was also characterized by its low content of ( E)-2-hexenal. The only clear trend observed during ripening of olives was the increase in the total content of esters. Therefore, the information obtained in this study is useful in selecting the proper harvest time for each cultivar according to the desired volatile compounds found in the oil. [ABSTRACT FROM AUTHOR]

The mycelium of the rice stem pathogen, Magnaporthe salvinii, secreted linoleate 9S-lipoxygenase (9S-LOX) and epoxy alcohol synthase (EAS). The EAS rapidly transformed 9S-hydroperoxy-octadeca-10E,12Z-dienoic acid (9S-HPODE) to threo 10 (11)-epoxy-9S-hydroxy-12Z-octadecenoic acid, but other hydroperoxy FAs were poor substrates. 9S-LOX was expressed in Pichia pastoris. Recombinant 9S-LOX oxidized 18:2n-6 directly to 9S-HPODE, the end product, and also to two intermediates, 11S-hydroperoxy-9Z,12Z-octadecenoic acid (11S-HPODE; ∼5%) and 13R-hydroperoxy-9Z,11E-octadecadienoic acid (13R-HPODE; ∼1%). 11S- and 13R-HPODE were isomerized to 9S-HPODE, probably after oxidation to peroxyl radicals, β-fragmentation, and oxygen insertion at C-9. The 18:3n-3 was oxidized at C-9, C-11, and C-13, and to 9,16-dihydroxy-10E,12,14E-octadecatrienoic acid. 9S-LOX contained catalytic manganese (Mn:protein ∼0.2:1; Mn/Fe, 1:0.05), and its sequence could be aligned with 77% identity to 13R-LOX with catalytic manganese lipoxygenase (13R-MnLOX) of the Take-all fungus. The Leu350Met mutant of 9S-LOX shifted oxidation of 18:2n-6 from C-9 to C-13, and the Phe347Leu, Phe347Val, and Phe347Ala mutants of 13R-MnLOX from C-13 to C-9. In conclusion, M. salvinii secretes 9S-LOX with catalytic manganese along with a specific EAS. Alterations in the Sloane determinant of 9S-LOX and 13R-MnLOX with larger and smaller hydrophobic residues interconverted the regiospecific oxidation of 18:2n-6, presumably by altering the substrate position in relation to oxygen insertion.

Soil or growing media salinity is an increasing problem in agriculture throughout the world. Therefore, there is a real interest in a better understanding of the mechanisms set by the plants to respond to this stress. The present study concerns tomato, which is one of the most important cultivated vegetables. Tomato seeds (Lycopersicon esculentum var. ‘Moneymaker’) were disinfected and a salt stress (NaCl 100 mM) was applied 8 days after the onset of germination. Samples were collected after 4 days of stress. In this study, attention was focused on the antioxidant system and the lipoxygenase pathway because salt stress is often associated with an increased production of reactive oxygen species and polyunsaturated fatty acids are one of the most susceptible targets to oxidative attacks. The perception of the stress by the plantlets was confirmed by the overexpression of an aquaporin-coding gene (aqua2). Concerning the antioxidant system, the activities of ascorbate peroxydase and catalase enzymes were studied but no significant variation was observed between stressed seedlings and controls. Similar results were obtained for ascorbate measurements. Complementarily, the lipoxygenase pathway was studied at three levels in the plantlets. The expression of two genes (lipoxygenase-A and oxo-phytodienoic acid reductase) was first followed at the mRNA level by RT-PCR. The oxylipin content was determined by HPLC and the lipoxygenase activity as well as the hydroperoxide degradation activity were measured spectrophotometrically. The obtained results indicate that no clear accumulation of oxylipin occurs in our stress conditions. However, an increase in lipoxygenase and hydroperoxide degradation activities was observed and seems to indicate that several enzymes of the lipoxygenase pathway are involved in the plant response to salt stress.

Brassicales release volatile glucosinolate breakdown products upon tissue mechanical damage, but it is unclear how the release of glucosinolate volatiles responds to abiotic stresses such as heat stress. We used three different heat treatments, simulating different dynamic temperature conditions in the field to gain insight into stress-dependent changes in volatile blends and photosynthetic characteristics in the annual herb Brassica nigra (L.) Koch. Heat stress was applied by either heating leaves through temperature response curve measurements from 20 to 40 °C (mild stress), exposing plants for 4 h to temperatures 25-44 °C (long-term stress) or shock-heating leaves to 45-50 °C. Photosynthetic reduction through temperature response curves was associated with decreased stomatal conductance, while the reduction due to long-term stress and collapse of photosynthetic activity after heat shock stress were associated with non-stomatal processes. Mild stress decreased constitutive monoterpene emissions, while long-term stress and shock stress resulted in emissions of the lipoxygenase pathway and glucosinolate volatiles. Glucosinolate volatile release was more strongly elicited by long-term stress and lipoxygenase product released by heat shock. These results demonstrate that glucosinolate volatiles constitute a major part of emission blend in heat-stressed B. nigra plants, especially upon chronic stress that leads to induction responses. [ABSTRACT FROM AUTHOR]

Olive fruit stoning gives rise to an important modification in olive oil aroma. The level of this modification is a function of the cultivar. An increment in the content of six-carbon compounds (C6) was observed in olive oils obtained from the cultivars Verdial and Manzanilla, but not in the cultivar Picual. In the three cultivars under study, contents of five-carbon compounds (C5) and esters decreased as a consequence of fruit stoning. The modification of olive oil aroma composition in the cultivar Verdial caused by olive fruit stoning was observed to be due both to tissue wounding and to the absence of the olive seed during the crushing-malaxation process to obtain olive oil aroma. Both factors contribute independently to the content modification of C6, C5 compounds and esters in the olive oil aroma from stoned fruits.