Effect of Heat Stress on Yield, Monoterpene Content and Antibacterial Activity of Essential Oils of Mentha x piperita var. Mitcham and Mentha arvensis var. piperascens.

Heat stress affects the yield of medicinal plants and can reduce biomass and/or metabolite production. In order to evaluate the effect of heat-induced stress on the essential oil production in Mentha x piperita L. var. Mitcham (Mitcham mint) and Mentha arvensis var. piperascens Malinv. ex L. H. Bailey (Japanese mint), we studied the chemical composition of the oils of the two mint species under different heat shock stresses in growth chambers. The antibacterial activity of the essential oils was also evaluated; microscopic observation (fluorescence and electron transmission) was used to assess the effect of the tested samples on bacterial growth. The results obtained shed light on the mint essential oils composition and biological activity in relation to heat stress.

Evaluation of Solasonine Content and Expression Patterns of SGT1 Gene in Different Tissues of Two Iranian Eggplant (Solanum melongena L.) Genotypes.

Eggplant (Solanum melongena L.) is one of the most consumed vegetables in the world. The eggplant glycoalkaloids (GAs) are toxic secondary metabolites that may have detrimental effects on human health, particularly if the magnitudes of GAs are higher than the recommended food safety level (200 mg per kg of fresh mass). In this study, the content of solasonine compound and the expression patterns of solasodine galactosyltransferase (SGT1) gene were assessed in different tissues (mature leaves, flower buds, young, mature, and physiologically ripe fruits) of two Iranian eggplant genotypes (D1 and J10) under field conditions. The maximum mass fraction of solasonine in D1 was detected in flower buds (135.63 µg/g), followed by leaf (113.29 µg/g), physiologically ripe fruit (74.74 µg/g), young fruit (61.33 µg/g), and mature fruit (21.55 µg/g). Comparing both genotypes, the genotype of bitter fruits (J10) contained higher mass fraction of solasonine, as one of the main factors for producing bitter flavour of the plant. Regarding the expression profiles of SGT1, in both genotypes, the activity of the gene was increased nearly parallel with the concentration of solasonine. In the J10 genotype, transcript level of the gene was significantly higher than the genotype of sweet fruits (D1). Although both D1 and J10 genotypes are possibly recommendable for human food consumption, D1 is more suitable for daily diet.

The antifungal eugenol perturbs dual aromatic and branched-chain amino acid permeases in the cytoplasmic membrane of yeast.

Eugenol is an aromatic component of clove oil that has therapeutic potential as an antifungal drug, although its mode of action and precise cellular target(s) remain ambiguous. To address this knowledge gap, a chemical-genetic profile analysis of eugenol was done using ∼4700 haploid Saccharomyces cerevisiae gene deletion mutants to reveal 21 deletion mutants with the greatest degree of susceptibility. Cellular roles of deleted genes in the most susceptible mutants indicate that the main targets for eugenol include pathways involved in biosynthesis and transport of aromatic and branched-chain amino acids. Follow-up analyses showed inhibitory effects of eugenol on amino acid permeases in the yeast cytoplasmic membrane. Furthermore, phenotypic suppression analysis revealed that eugenol interferes with two permeases, Tat1p and Gap1p, which are both involved in dual transport of aromatic and branched-chain amino acids through the yeast cytoplasmic membrane. Perturbation of cytoplasmic permeases represents a novel antifungal target and may explain previous observations that exposure to eugenol results in leakage of cell contents. Eugenol exposure may also contribute to amino acid starvation and thus holds promise as an anticancer therapeutic drug. Finally, this study provides further evidence of the usefulness of the yeast Gene Deletion Array approach in uncovering the mode of action of natural health products.

Analysis of the proteome of common bean (Phaseolus vulgaris L.) roots after inoculation with Rhizobium etli.

Proteomics techniques were used to identify the underlying mechanism of the early stage of symbiosis between the common bean (Phaseolus vulgaris L.) and bacteria. Proteins from roots of common beans inoculated with bacteria were separated using two-dimensional polyacrylamide gel electrophoresis and identified using mass spectrometry. From 483 protein spots, 29 plant and 3 bacterial proteins involved in the early stage of symbiosis were identified. Of the 29 plant proteins, the expression of 19 was upregulated and the expression of 10 was downregulated. Upregulated proteins included those involved in protein destination/storage, energy production, and protein synthesis; whereas the downregulated proteins included those involved in metabolism. Many upregulated proteins involved in protein destination/storage were chaperonins and proteasome subunits. These results suggest that defense mechanisms associated with induction of chaperonins and protein degradation regulated by proteasomes occur during the early stage of symbiosis between the common bean and bacteria.

A comparative proteomic analysis of the early response to compatible symbiotic bacteria in the roots of a supernodulating soybean variety.

To reveal the processes involved in the early stages of symbiosis between soybean plants and root nodule bacteria, we conducted a proteomic analysis of the response to bacterial inoculation in the roots of supernodulating (En-b0-1) and non-nodulating (En1282) varieties, and their parental normal-nodulating variety (Enrei). A total of 56 proteins were identified from 48 differentially expressed protein spots in normal-nodulating variety after bacterial inoculation. Among 56 proteins, metabolism- and energy production-related proteins were upregulated in supernodulating and downregulated in non-nodulating varieties compared to normal-nodulating variety. The supernodulating and non-nodulating varieties responded oppositely to bacterial inoculation with respect to the expression of 11 proteins. Seven proteins of these proteins was downregulated in supernodulating varieties compared to non-nodulating variety, but expression of proteasome subunit alpha type 6, gamma glutamyl hydrolase, glucan endo-1,3-beta glucosidase, and nodulin 35 was upregulated. The expression of seven proteins mirrored the degree of nodule formation. At the transcript level, expression of stem 31kDa glycoprotein, leucine aminopeptidase, phosphoglucomutase, and peroxidase was downregulated in the supernodulating variety compared to the non-nodulating variety, and their expression in the normal-nodulating variety was intermediate. These results suggest that suppression of the autoregulatory mechanism in the supernodulating variety might be due to negative regulation of defense and signal transduction-related processes.

A proteomics view on the role of drought-induced senescence and oxidative stress defense in enhanced stem reserves remobilization in wheat.

Drought is one of the major factors limiting the yield of wheat (Triticum aestivum L.) particularly during grain filling. Under terminal drought condition, remobilization of pre-stored carbohydrates in wheat stem to grain has a major contribution in yield. To determine the molecular mechanism of stem reserve utilization under drought condition, we compared stem proteome patterns of two contrasting wheat landraces (N49 and N14) under a progressive post-anthesis drought stress, during which period N49 peduncle showed remarkably higher stem reserves remobilization efficiency compared to N14. Out of 830 protein spots reproducibly detected and analyzed on two-dimensional electrophoresis gels, 135 spots showed significant changes in at least one landrace. The highest number of differentially expressed proteins was observed in landrace N49 at 20days after anthesis when active remobilization of dry matter was observed, suggesting a possible involvement of these proteins in effective stem reserve remobilization of N49. The identification of 82 of differentially expressed proteins using mass spectrometry revealed a coordinated expression of proteins involved in leaf senescence, oxidative stress defense, signal transduction, metabolisms and photosynthesis which might enable N49 to efficiently remobilized its stem reserves compared to N14. The up-regulation of several senescence-associated proteins and breakdown of photosynthetic proteins in N49 might reflect the fact that N49 increased carbon remobilization from the stem to the grains by enhancing senescence. Furthermore, the up-regulation of several oxidative stress defense proteins in N49 might suggest a more effective protection against oxidative stress during senescence in order to protect stem cells from premature cell death. Our results suggest that wheat plant might response to soil drying by efficiently remobilize assimilates from stem to grain through coordinated gene expression.