The isolation of methyl β-orsellinate from Stereocaulon alpinum and comments on the isolation of 4,6-dihydroxy-2- methoxy-3-methylacetophenone from stereocaulon species

Methyl β-orsellinate has been isolated from chloroform extracts of Stereocaulon alpinum. It is shown that methyl β-orsellinate was probably previously misidentified as 4,6-dihydroxy-2-methoxy-3-methylacetophenone during work on Stereocaulon vesuvianum. Reports of the isolation of the latter thus appear to be erroneous. The status of methyl β-orsellinate as a naturally occurring metabolite is discussed.     

Structure of vesuvianic acid from stereocaulon species

Vesuvianic acid, which was previously isolated from Stereocaulon vesuvianum var. pulvinatum without a full elucidation of structure, has now been isolated from S. alpinum. More detailed spectral investigation indicates that vesuvianic acid, which was previously believed to be a new depsidone, is an ethyl ether of stictic acid which itself may be an artefact produced during extraction.     

Stereocaulon cumulatum comb. nov., another crustose species in the genus

Abstract:The new combination Stereocaulon cumulatum (Sommerf.) Timdal is made for the northern Eurasian and Greenlandic, arctic-alpine, terricolous lichen presently known as Toninia cumulata (Sommerf.) Th. Fr.     

Structural diversity of d-galacto-d-mannan components isolated from lichens having ascomycetous mycosymbionts

d-Galacto-d-mannan fractions were isolated from six common Canadian lichens having ascomycetous mycosymbionts, namely Parmelia sulcata, Stereocaulon paschale, Peltigera aphthosa, Letharia vulpina, Actinogyra muehlenbergii, and an Usnea sp. Their chemical structures were compared with each other and those of six species previously investigated; only Parmelia sulcata and Cetraria islandica (Iceland moss) contained galactomannans of closely related structures. The structural diversity depends on substituents on the (1→6)-linked α-d-mannopyranosyl main-chains. The side-chains occur as monosubstituents at O-2 or O-4 or as disubstituents at O-2,4. Frequently, the main-chain units are unsubstituted. Thus far, eight types of substitution have been recognized (1–8) in which β-d-Galp is linked (1→4), α-d-Galp and α-d-Manp (1→2), and β-d-Galf (1→4).     

ψ-esters of depsidones with a lactole ring

The reaction of stictic, norstictic and salazinic acids with methanol, ethanol and tert-butanol has been investigated. 8′-O-Methylstictic acid is identical with methylstictic acid from Lobaria oregana. Ingolfdottir's vesuvianic acid from Stereocaulon vesuvianum and Handong's cetrariastrumin from Cetrariastrum nepalensis have been shown to be 8′-O-ethylstictic acid and 8′,9′-di-O-ethylsalazinic acid, respectively, by reaction of stictic and salazinic acids with ethanol.     

Antimitotic activity of lobaric acid and a new benzofuran,sakisacaulon A from Stereocaulon sasakii

Lobaric acid (1) has been isolated from lichen, Stereocaulon sasakii together with a new benzofuran, sakisacaulon A (2). Lobaric acid (1) inhibited the polymerization of tubulin. Structure–activity relationship of lobaric acid and its derivatives on inhibitory activity of tubulin polymerization was discussed.     

Lobaric acid and pseudodepsidones inhibit NF-κB signaling pathway by activation of PPAR-γ

Herein we report the anti-inflammatory activity of lobaric acid and pseudodepsidones isolated from the nordic lichen Stereocaulon paschale. Lobaric acid (1) and three compounds (2, 7 and 9) were found to inhibit the NF-κB activation and the secretion of pro-inflammatory cytokines (IL-1β and TNF-α) in LPS-stimulated macrophages. Inhibition and docking simulation experiments provided evidence that lobaric acid and pseudodepsidones bind to PPAR-γ between helix H3 and the beta sheet, similarly to partial PPAR-γ agonists. These findings suggest that lobaric acid and pseudodepsidones reduce the expression of pro-inflammatory cytokines by blocking the NF-κB pathway via the activation of PPAR-γ.     

Short-term effects of enhanced UV-B and CO2 on lichens at different latitudes

Interaction effects of UV-B and CO₂ on three lichens species, Cladonia arbusculo, Cetraria islandica and Stereocaulon paschale, from two latitudinal sites, 68∘N and 56∘N, were studied in a laboratory experiment. The response of the plants was recorded by measuring their chlorophyll fluorescence. All species had a similar response to enhanced UV-B depending on the latitude from which the population came and the time of the season when they were sampled. Overall, there was a significant increase in photosystem II yield (as measured by a fluorescence technique) due to UV-B and no separate effect due to enhanced CO₂, although there was a significant interaction between CO₂ and UV-B. The increase due to UV-B was at the low CO₂ level. There were also significant differences in response due to latitude. The results contradict our hypotheses that negative effects of UV-B would be larger in the North than in the South and that a negative response should be especially large during the early season.     

Leightoniella zeylanensis belongs to the Pannariaceae

Recent finds of Leightoniella zeylanensis, classified variously in the Collemataceae and Pannariaceae, enabled us to generate DNA sequence data for investigating its phylogenetic affiliation. Newly generated sequence data from the internal transcribed spacer (ITS) region and the large subunit of the nuclear ribosomal DNA (nrLSU), the small subunit of the mitochondrial ribosomal (mrSSU) DNA, and the largest subunit of the RNA polymerase II gene (RPB1) indicate that L. zeylanensis is a member of the Pannariaceae, belonging to a strongly supported clade together with Physma, Lepidocollema, and Gibbosporina (= the ‘Physma clade’). With the currently available data, however, relationships within this clade are largely impossible to reconstruct with confidence. Leightoniella zeylanensis was found to possess ellipsoid ascospores surrounded by a thick, gelatinous perispore with pointed ends, supporting a previously published hypothesis that such a perispore type is a synapomorphy for the Physma clade. A lectotype is designated for the basionym Pterygium zeylanense Leight.     

Nutritive value of terricolous lichens for reindeer in winter

Abstract:In contrast to virtually all other species of ruminants, reindeer (Rangifer tarandus) eat substantial amounts of lichens in winter. Several different species of lichens are eaten and most are highly palatable. The chemical composition and the in vitro digestibility of six species of terricolous lichens commonly eaten by reindeer were measured. Ruminal inoculum was obtained in winter from six free-ranging reindeer that had been grazing on natural pastures in northern Norway. Analysis of the plant parts recovered from their rumens confirmed that the animals had been eating a mixed diet that included both lichens and vascular plants. The chemical composition and the in vitro digestibility of the different species of lichens varied considerably between species and genera. Cetraria islandica, C. nivalis andCladonia arbuscula were highly digestible [69–77% dry matter (DM)], Stereocaulon paschale was poorly digestible (43% DM), whereas Cladonia stellaris and C. gracilis had an intermediate digestibility (56–57% DM). Mixing Cladonia stellaris with vascular plants (50:50) had no effect on the in vitro digestibility of the combined substrates. The in vitro digestibility of Cladonia stellaris in inoculum from two captive reindeer which had had no access to lichens was very low (10% DM). This shows that the source of inoculum used for digestibility trials has a major effect on the apparent digestibility of the substrates. Evidently, the extent to which reindeer are able to utilize lichens depends on the species that are selected and on what the animals have been eating recently.     

Protein tyrosine phosphatase 1B inhibitory effects of depsidone and pseudodepsidone metabolites from the Antarctic lichen Stereocaulon alpinum

Seven phenolic lichen metabolites (1–7) have been isolated from a methanol extract of the Antarctic lichen Stereocaulon alpinum by various chromatographic methods. The structures of these compounds were determined mainly by analysis of NMR spectroscopic data. A depsidone-type compound, lobaric acid (1) and two pseudodepsidone-type compounds, 2 and 3, exhibited potent inhibitory activity against protein tyrosine phosphatase 1B (PTP1B) with IC₅₀ values of 0.87 μM, 6.86 μM, and 2.48 μM, respectively. Kinetic analyses of PTP1B inhibition by compounds 1 and 2 suggested that these compounds inhibited PTP1B activity in a non-competitive manner.     

Depsides: Lichen Metabolites Active against Hepatitis C Virus

A thorough phytochemical study of Stereocaulon evolutum was conducted, for the isolation of structurally related atranorin derivatives. Indeed, pilot experiments suggested that atranorin (1), the main metabolite of this lichen, would interfere with the lifecycle of hepatitis C virus (HCV). Eight compounds, including one reported for the first time (2), were isolated and characterized. Two analogs (5, 6) were also synthesized, to enlarge the panel of atranorin-related structures. Most of these compounds were active against HCV, with a half-maximal inhibitory concentration of about 10 to 70 µM, with depsides more potent than monoaromatic phenols. The most effective inhibitors (1, 5 and 6) were then added at different steps of the HCV lifecycle. Interestingly, atranorin (1), bearing an aldehyde function at C-3, inhibited only viral entry, whereas the synthetic compounds 5 and 6, bearing a hydroxymethyl and a methyl function, respectively, at C-3 interfered with viral replication.     

Functional characteristics of a fruticose type of lichen, Stereocaulon foliolosum Nyl. in response to light and water stress

Stereocaulon foliolosum a fruticose type of lichen under its natural habitat is subjected to low temperature, high light conditions and frequent moisture stress due its rocky substratum. To understand as to how this lichen copes up with these stresses, we studied the reflectance properties, light utilization capacity and the desiccation tolerance under laboratory conditions. S. foliolosum showed light saturation point for photosynthesis at 390 μmol CO₂ m^?2 s^?1 and the light compensation point for photosynthesis at 64 μmol CO₂ m^?2 s^?1. Our experiments show that S. foliolosum has a low absorptivity (30–35 %) towards the incident light. The maximum rates of net photosynthesis and apparent electron transport observed were 1.9 μmol CO₂ m^?2 s^?1 and 45 μmol e^? m^?2 s^?1, respectively. The lichen recovers immediately after photoinhibition under low light conditions. S. foliolosum on subjecting to desiccation results in the decrease of light absorptivity and the reflectance properties associated with water status of the thalli show a change. During desiccation, a simultaneous decrease in photosynthesis, dark respiration and quenching in the fluorescence properties was observed. However, all the observed changes show a rapid recovery on rewetting the lichen. Our study shows that desiccation does not have a severe or long-term impact on S. foliolosum and the lichen is also well adapted to confront high light intensities.     

Nitrogenase Activity in the Lichen Stereocaulon paschale: Recovery after Dry Storage

The effect of prolonged storage on nitrogenase activity in Stereocaulon paschale (L.) Fr. was studied. The thalli had a very low water content during the storage over silica gel at 4°C in the dark. For C₂H₂-reduction measurements the lichen samples were remoistened and held at 15°C in the light for 1–36 h before the addition of C₂H₂. With the longest pre-incubation time preceding the nitrogenase activity measurements there was no significant decrease in nitrogenase activity during 75 weeks of storage. The method of storage was simple and inexpensive and the nitrogenase activity characteristic of each lichen batch, due to seasonal variation, was well preserved during the storage.     

猪圆环病毒2型（PCV2）核衣壳蛋白免疫原性的鉴定和应用及其多抗在PCV2感染诊断中的应用

猪圆环病毒2型ORF2编码与病毒毒力相关的结构蛋白--核衣壳蛋白(Cap),该蛋白可以用于PCV2感染的血清学调查,但不同区域的PCV2分离株的ORF2特别是其抗原表位序列存在一定的突变.本研究将PCV2浙江分离株ORF2的主要抗原表位以及PCV1 ORF2进行了原核表达,将分别纯化的融合蛋白Cap2s和Cap1s免疫SPF兔后制备多抗,并进一步分析了纯化蛋白的免疫原性和多抗的特性.Western blot结果表明无论Cap2s和Cap1s均能与两个多抗发生交叉反应,而PCV2或PCV1阳性猪血清只能分别特异性地识别Cap2s和Cap1s.IFA结果则证明两个多抗对于天然Cap蛋白无交叉反应性.利用Cap2s作为包被抗原对13个猪场的259份血清样品的PCV2抗体进行ELISA检测,平均阳性率为80.69%(209/259),而各猪场的阳性率差异较大(48.28%～100%).以上结果表明Cap2s可作为一个型特异性抗原用于浙江省本地猪场猪群血清中PCV2抗体的监控,而其多抗也可用于免疫组化对PCV2感染进行有效诊断.     

中国珊瑚枝属地衣的特殊种

Stereocaulon incrustatum, a new record in China, and St. massartianum and St. sorediiferum have several special chemical races, and the absence of atranorin in the genus is reported for the first time. Investigation results show that chemistry is not very important in taxonomy of the genus. Evolutionally, the cephalodia of St. incrustatum are possibly a transition characteristic from poorly developed cortex to protosacculate cephalodia.     

Do lichens domesticate photobionts like farmers domesticate crops? Evidence from a previously unrecognized lineage of filamentous cyanobacteria

Phylogenetic diversity of lichen photobionts is low compared to that of fungal counterparts. Most lichen fungi are thought to be associated with just four photobiont genera, among them the cyanobacteria Nostoc and Scytonema, two of the most important nitrogen fixers in humid ecosystems. Although many Nostoc photobionts have been identified using isolated cultures and sequences, the identity of Scytonema photobionts has never been confirmed by culturing or sequencing. We investigated the phylogenetic placement of presumed Scytonema photobionts and unicellular morphotypes previously assigned to Chroococcus, from tropical Dictyonema, Acantholichen, Coccocarpia, and Stereocaulon lichens. While we confirm that filamentous and unicellular photobiont morphotypes belong to a single clade, this clade does not cluster with Scytonema but represents a novel, previously unrecognized, highly diverse, exclusively lichenized lineage, for which the name Rhizonema is available. The phylogenetic structure observed in this novel lineage suggests absence of coevolution with associated mycobionts at the species or clade level. Instead, highly efficient photobiont strains appear to have evolved through photobiont sharing between unrelated, but ecologically similar, coexisting lineages of lichenized fungi ("lichen guilds"), via the selection of particular photobiont strains through and subsequent horizontal transfer among unrelated mycobionts, a phenomenon not unlike crop domestication.     

Noteworthy species of Stereocaulon from China

Stereocaulon incrustatum, a new record in China, and St. massartianum and St. sorediiferum have several special chemical races, and the absence of atranorin in the genus is reported for the first time. Investigation results show that chemistry is not very important in taxonomy of the genus. Evolutionally, the cephalodia of St. incrustatum are possibly a transition characteristic from poorly developed cortex to protosacculate cephalodia.