Compensation and resistance to herbivory in seagrasses: induced responses to simulated consumption by fish

Herbivory can induce changes in plant traits that may involve both tolerance mechanisms that compensate for biomass loss and resistance traits that reduce herbivore preference. Seagrasses are marine vascular plants that possess many attributes that may favour tolerance and compensatory growth, and they are also defended with mechanisms of resistance such as toughness and secondary metabolites. We quantified phenotypic changes induced by herbivore damage on the temperate seagrass Posidonia oceanica in order to identify specific compensatory and resistance mechanisms in this plant, and to assess any potential trade-offs between these two strategies of defence. We simulated three natural levels of fish herbivory by repeatedly clipping seagrass leaves during the summer period of maximum herbivory. Compensatory responses were determined by measuring shoot-specific growth, photosynthetic rate, and the concentration of nitrogen and carbon resources in leaves and rhizomes. Induced resistance was determined by measuring the concentration of phenolic secondary metabolites and by assessing the long-term effects of continued clipping on herbivore feeding preferences using bioassays. Plants showed a significant ability to compensate for low and moderate losses of leaf biomass by increasing aboveground growth of damaged shoots, but this was not supported by an increase in photosynthetic capacity. Low levels of herbivory induced compensatory growth without any measurable effects on stored resources. In contrast, nitrogen reserves in the rhizomes played a crucial role in the plant’s ability to compensate and survive herbivore damage under moderate and high levels of herbivory, respectively. We found no evidence of inducibility of long-term resistance traits in response to herbivory. The concentration of phenolics decreased with increasing compensatory growth despite all treatments having similar carbon leaf content, suggesting reallocation of these compounds towards primary functions such as cell-wall construction.     

天然酚类色素的研究与应用进展

植物花色素的研究已经非常广泛和深入,多酚类化合物作为重要的天然食用色素越来越受到人们的重视.本文结合近年来的最新研究成果,从酚类色素的种类与结构、理化性质、提纯与鉴定、稳定性及影响因素、生物功能和应用价值等方面进行了综述,并对酚类的研究热点进行了展望,对人们全面认识和开发利用酚类色素具有一定的参考文献:价值.     

Alginate,mannitol, phenolic compounds and biological activities of two range-extending brown algae, <Emphasis Type="Italic">Sargassum mangarevense</Emphasis> and <Emphasis Type="Italic">Turbinaria ornata</Emphasis> (Phaeophyta: Fucales), from Tahiti (French Polynesia)

This study deals with two range-extending brown algae from Tahitian coral reefs, Sargassum mangarevense and Turbinaria ornata; their alginate properties, mannitol and phenolic contents, antioxidant and antimicrobial activities were determined. Turbinaria ornata showed the richest alginate content with the highest extraction yield (19.2 ± 1.3% dw). Their alginates also exhibited the highest viscosity (50 ± 18 mPa.s), but the M:G ratios (mannuronic acid to glucuronic acid) of alginates (1.25–1.42) were similar in both species. Alginate yield displayed spatial variations, but no significant seasonal changes. The highest mannitol content was found in S. mangarevense (12.2 ± 2.1% dw) during the austral winter. With respect to other tropical Fucales, both algae exhibited also a high phenolic content (2.45–2.85% dw) with significant spatio-temporal variations. Furthermore, high antioxidant activity and activity against Staphylococcus aureus were also detected in extracts. According to these preliminary results, these two range-extending algae are of key interest in numerous industrial areas.     

Effect of dihydrocaffeic acid on UV irradiation of human keratinocyte HaCaT cells

Dihydrocaffeic acid, a dietary constituent and a microbial metabolite of flavonoids, is an antioxidant, but few biological effects have been examined. After its production by microflora in the colon, dihydrocaffeic acid is absorbed and found in plasma as a combination of free and metabolized forms. Excess solar UV radiation provokes damage and initiates immune response and inflammation in skin, sometimes leading to cancer. Dihydrocaffeic acid reduced the cytotoxicity and pro-inflammatory cytokine production (interleukin-6 and -8) in HaCaT cells, a keratinocyte model, following UV radiation. The effect of dihydrocaffeic acid may result from a combination of direct radical scavenging of the reactive oxygen species formed or reinforcement of the antioxidant potential of the keratinocytes, as well as a direct interference with the pathway involved in cytokine stimulation. The minimum structure required for such an effect appears to consist of a propionate side chain attached to a catechol moiety, as indicated by the efficacy of caffeic acid, but not of the methyl and glucuronide conjugates of dihydrocaffeic acid. The data obtained suggest that dihydrocaffeic acid is a potential candidate for photo-protection by interfering with the events initiated after UV exposure in keratinocytes.     

Mycoplasma fermentans glycolipid-antigen as a pathogen of rheumatoid arthritis

Mycoplasma fermentans has been suspected as one of the causative pathogenic microorganisms of rheumatoid arthritis (RA) however, the pathogenic mechanism is still unclear. We, previously, reported that glycolipid-antigens (GGPL-I and III) are the major antigens of M. fermentans. Monoclonal antibody against the GGPL-III could detect the existence of the GGPL-III antigens in synovial tissues from RA patients. GGPL-III antigens were detected in 38.1% (32/84) of RA patient’s tissues, but not in osteoarthritis (OA) and normal synovial tissues. Immunoelectron microscopy revealed that a part of GGPL-III antigens are located at endoplasmic reticulum. GGPL-III significantly induced TNF-α and IL-6 production from peripheral blood mononulear cells, and also proliferation of synovial fibroblasts. Further study is necessary to prove that M. fermentans is a causative microorganism of RA; however, the new mechanisms of disease pathogenesis provides hope for the development of effective and safe immunotherapeutic strategies based on the lipid-antigen, GGPL-III, in the near future.     

杉木解酚菌的研究

从杉木林土壤中筛选到5株高效解酚菌(F2、F3、F4、F7、F15),结果表明,F4、F33d,F2、F155d能将600rng     

Microbial conversion of n-alkanes into glycolipid biosurfactants, mannosylerythritol lipids, by Pseudozyma (Candida antarctica)

n-Alkanes ranging from C₁₂ to C₁₈ were converted into glycolipid biosurfactants, mannosylerythritol lipids (MEL), by resting cells of Pseudozyma (Candida) antarctica T-34. The highest yield (0.87 g g^–1 substrate) was obtained from 6% (v/v) of n-octadecane after 7 days reaction. The amount of MEL reached 140 g l^–1 by intermittent feeding of the substrate.     

A chemosystematically significant 6,8,11-trihydroxygermacrane derivative from the New Zealand Apiaceae Anistome pilifera

Roots of Anisotome pilifera yielded typical Apiaceae compounds 6,7-dimethoxy-coumarin 1 and falcarindiol 2, plus the irregular diterpenes anisotomenoic acid 3 and anisotomene alcohol 4. The new germacrane derivative 8-O-senecioyl-6β,8α,11-trihydroxygermacra-1(10)E,4E-diene 5 was also isolated and the structure established by means of high resolution mass spectrometry and 1-D and 2-D NMR spectroscopy. Distribution and chemosystematic significance of 6,8-dihydroxygermacra-1(10)E,4E-dienes and 6,8,11-trihydroxygermacra-1(10)E,4E-dienes are discussed. Additionally, leaves of A. pilifera yielded chlorogenic acid 6 and high amounts of luteolin 7-O-α- -rhamnosyl(1→6)-β- -glucoside 7.     

Biotransformation of phenolic compounds by the cultured cells of Catharanthus roseus

The cultured cells of Catharanthus roseus were able to convert 2-, 3-, and 4-hydroxybenzyl alcohols into their corresponding hydroxybenzyl-β- -glucopyranosides or β- -glucopyranosylbenzyl alcohols, and then convert 2- and 3-hydroxybenzyl-β- -glucopyranosides into primeverosides and vicianosides. Further, the C. roseus cells were capable of hydroxylation of 2-hydroxybenzoic acid to afford 2,5-dihydroxybenzoic acid and then glucosylation of the newly introduced phenolic hydroxyl group.     

Chemical constituents from the stem bark of Acer tegmentosum

A new phenolic glycoside, 4-hydroxyphenylethyl-1-O-β-D-[6′-O-(4-hydroxybenzoyl)]-glucopyranoside (1) was isolated from the stem bark of Acer tegmentosum, along with seven known phenolic compounds (2–8). The structure of compound 1 was determined by spectral analyses, including HR-ESI-MS, 1D and 2D NMR (COSY, HMQC and HMBC) experiments. Compounds 3 and 4 were found in the family Aceraceae for the first time.