Catabolism of l–methionine in the formation of sulfur and other volatiles in melon (Cucumis melo L.) fruit

Sulfur‐containing aroma volatiles are important contributors to the distinctive aroma of melon and other fruits. Melon cultivars and accessions differ in the content of sulfur‐containing and other volatiles. l –methionine has been postulated to serve as a precursor of these volatiles. Incubation of melon fruit cubes with ¹³C‐ and ²H‐labeled l –methionine revealed two distinct catabolic routes into volatiles. One route apparently involves the action of an l ‐methionine aminotransferase and preserves the main carbon skeleton of l ‐methionine. The second route apparently involves the action of an l ‐methionine‐γ–lyase activity, releasing methanethiol, a backbone for formation of thiol‐derived aroma volatiles. Exogenous l ‐methionine also generated non‐sulfur volatiles by further metabolism of α–ketobutyrate, a product of l ‐methionine‐γ–lyase activity. α–Ketobutyrate was further metabolized into l –isoleucine and other important melon volatiles, including non‐sulfur branched and straight‐chain esters. Cell‐free extracts derived from ripe melon fruit exhibited l ‐methionine‐γ–lyase enzymatic activity. A melon gene (CmMGL) ectopically expressed in Escherichia coli, was shown to encode a protein possessing l ‐methionine‐γ–lyase enzymatic activity. Expression of CmMGL was relatively low in early stages of melon fruit development, but increased in the flesh of ripe fruits, depending on the cultivar tested. Moreover, the levels of expression of CmMGL in recombinant inbred lines co‐segregated with the levels of sulfur‐containing aroma volatiles enriched with +1 m/z unit and postulated to be produced via this route. Our results indicate that l ‐methionine is a precursor of both sulfur and non‐sulfur aroma volatiles in melon fruit.     

Regulation of glial cyclooxygenase by bradykinin

The aim of the present study was to investigate the short-term effect of bradykinin on the two cyclooxygenase species in neonatal rat glial cells. In spite of the fact that cyclooxygenase protein levels were not altered, an increase in cyclooxygenase activity was observed. Use of cyclooxygenase-1 inhibitors and paracetamol resulted in complete elimination of the bradykinin-induced prostaglandin E(2) synthesis and of cyclooxygenase enzyme activity. Cyclooxygenase-2 inhibitors only partially inhibited enzyme activity and prostaglandin production. Our data suggest that cyclooxygenase-1 is probably the major contributor to short-term modulation of glial prostaglandin E2 synthesis by bradykinin.     

mRNAs encoding polarity and exocytosis factors are cotransported with the cortical endoplasmic reticulum to the incipient bud in Saccharomyces cerevisiae

Polarized growth in the budding yeast Saccharomyces cerevisiae depends upon the asymmetric localization and enrichment of polarity and secretion factors at the membrane prior to budding. We examined how these factors (i.e., Cdc42, Sec4, and Sro7) reach the bud site and found that their respective mRNAs localize to the tip of the incipient bud prior to nuclear division. Asymmetric mRNA localization depends upon factors that facilitate ASH1 mRNA localization (e.g., the 3' untranslated region, She proteins 1 to 5, Puf6, actin cytoskeleton, and a physical association with She2). mRNA placement precedes protein enrichment and subsequent bud emergence, implying that mRNA localization contributes to polarization. Correspondingly, mRNAs encoding proteins which are not asymmetrically distributed (i.e., Snc1, Mso1, Tub1, Pex3, and Oxa1) are not polarized. Finally, mutations which affect cortical endoplasmic reticulum (ER) entry and anchoring in the bud (myo4Delta, sec3Delta, and srp101) also affect asymmetric mRNA localization. Bud-localized mRNAs, including ASH1, were found to cofractionate with ER microsomes in a She2- and Sec3-dependent manner; thus, asymmetric mRNA transport and cortical ER inheritance are connected processes in yeast.     

Enrichment of tomato flavor by diversion of the early plastidial terpenoid pathway

We have modified the flavor and aroma of tomatoes by expressing the Ocimum basilicum geraniol synthase gene under the control of the tomato ripening-specific polygalacturonase promoter. A majority of untrained taste panelists preferred the transgenic fruits over controls. Monoterpene accumulation was at the expense of reduced lycopene accumulation. Similar approaches may be applicable for carotenoid-accumulating fruits and flowers of other species.     

Body size influences differently the detectabilities of colour morphs of cryptic prey

Body size and coloration may contribute to variation in performance and fitness among individuals; for example, by influencing vulnerability to predators. Yet, the combined effect of size and colour pattern on susceptibility to visual predators has received little attention, particularly in camouflaged prey. In the colour polymorphic pygmy grasshopper Tetrix subulata (Linnaeus, 1758), females are larger than males, although there is a size overlap between sexes. In the present study, we investigated how body size and colour morph influenced detection of these grasshoppers, and whether differences in protective value among morphs change with size. We conducted a computer‐based experiment and compared how human ‘predators’ detected images of large, intermediate or small grasshoppers belonging to black, grey or striped colour morphs when embedded in photographs of natural grasshopper habitats. We found that time to detection increased with decreasing size, that differences in time to detection of the black, grey and striped morphs depended differently on body size, and that no single morph provided superior or inferior protection in all three size classes. By comparing morph frequencies in samples of male and female grasshoppers from natural populations, we also examined whether the joint effects of size and colour morph on detection could explain evolutionary dynamics in the wild. Morph frequency differences between sexes were largely in accordance with expectations from the results of the detection experiment. The results of the present study demonstrate that body size and colour morph can interactively influence detection of camouflaged prey. This may contribute to the morph frequency differences between male and female pygmy grasshoppers in the wild. Such interactive effects may also influence the dynamics of colour polymorphisms, and contribute to the evolution of ontogenetic colour change and sexual dichromatism. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 112–122.     

Pollen on-twine for food provisioning and oviposition of predatory mites in protected crops

The establishment of predatory mites on protected crops is affected by the availability of shelter and alternative food. We suggest that a pollen covered twine, coined here “pollen on-twine”, may provide these necessities when attached to the plant. We evaluated the effect of twine types and two pollen species on the establishment of Euseius scutalis (Athias-Henriot) and Amblyseius swirskii Athias-Henriot on pre-flowering pepper plants in a growth chamber. For both phytoseiids, rayon jute twine was found more beneficial while corn and oak pollen did not differ in their effect. Though populations of both predators were best promoted when twine and pollen were applied separately, E. scutalis population increased by more than tenfold and A. swirskii doubled when plants were applied with pollen on-twine. We propose that after further refining, pollen on-twine can serve as a feasible solution for predatory mite establishment on protected crops.     

Reduced predation risk for melanistic pygmy grasshoppers in post‐fire environments

The existence of melanistic (black) color forms in many species represents interesting model systems that have played important roles for our understanding of selective processes, evolution of adaptations, and the maintenance of variation. A recent study reported on rapid evolutionary shifts in frequencies of the melanistic forms in replicated populations of Tetrix subulata pygmy grasshoppers; the incidence of the melanistic form was higher in recently burned areas with backgrounds blackened by fire than in nonburned areas, and it declined over time in postfire environments. Here, we tested the hypothesis that the frequency shifts of the black color variant were driven, at least in part, by changes in the selective regime imposed by visual predators. To study detectability of the melanistic form, we presented human “predators” with images of black grasshoppers and samples of the natural habitat on computer screens. We demonstrate that the protective value of black coloration differs between burnt and nonburnt environments and gradually increases in habitats that have been more blackened by fire. These findings support the notion that a black color pattern provides improved protection from visually oriented predators against blackened backgrounds and implicate camouflage and predation as important drivers of fire melanism in pygmy grasshoppers.