Search

The Trebouxia photobiont freshly isolated from Xanthoria parietina (L.) Th. Fr. was used to develop a live cell chondriome (mitochondrial DNA) labelling method. In the initial phase six candidate dyes were tested and compared for mitochondrial labelling utility as assessed by the signal to noise ratio (SNR) of the mitochondrial signal to the adjacent cellular background in standardized confocal images of 30 labelled cells. DIOC7, JC-1 and MitoTracker orange (MTO) dyes showed some labelling ability. MTO had significantly higher utility than the other dyes. In a second phase, MTO concentration was optimized. The final labelling protocol was a 30 minute incubation with 1 μM of MTO. The resultant labelling was suitable for both widefield and confocal microscopy. Both 2D thresholding and 3D volume construction are demonstrated using the resultant data. The protocol can therefore be utilized for both qualitative research and for quantitative measurement of the chondriome in Trebouxia photobionts. This will facilitate a wide range of mitochondrial investigations in lichenology. [ABSTRACT FROM AUTHOR]

The new lichenicolous fungus Capronia suijae growing on the thallus of corticolous Xanthoria parietina is described from Belarus and compared with similar species. In addition to its host selection, the species is characterized by comparatively small ascomata, 40–80 μm diam., and (0–1–)3-septate ascospores, 9·5–11·5×4·0–5·0 μm. A key to the lichenicolous fungi growing on Xanthoria s. str. is provided. [ABSTRACT FROM AUTHOR]

The green algal photobionts of 12 Xanthoria, seven Xanthomendoza, two Teloschistes species and Josefpoeltia parva (all Teloschistaceae) were analyzed. Xanthoria parietina was sampled on four continents. More than 300 photobiont isolates were brought into sterile culture. The nuclear ribosomal internal transcribed spacer region (nrITS; 101 sequences) and the large subunit of the RuBiSco gene (rbcL; 54 sequences) of either whole lichen DNA or photobiont isolates were phylogenetically analyzed. ITS and rbcL phylogenies were congruent, although some subclades had low bootstrap support. Trebouxia arboricola,T. decolorans and closely related, unnamed Trebouxia species, all belonging to clade A, were found as photobionts of Xanthoria species. Xanthomendoza species associated with either T. decolorans (clade A), T. impressa, T. gelatinosa (clade I) or with an unnamed Trebouxia species. Trebouxia gelatinosa genotypes (clade I) were the photobionts of Teloschistes chrysophthalmus,T. hosseusianus and Josefpoeltia parva. Only weak correlations between distribution patterns of algal genotypes and environmental conditions or geographical location were observed. [ABSTRACT FROM PUBLISHER]

The genetic diversity within and among populations of Xanthoria parietina was studied at the subspecific level with a fingerprinting technique (RAPD-PCR) applied to sterile cultured multi-spore isolates, each being derived from a single apothecium. Populations from coastal, rural and urban sites from NW, SW and central France and from NE Switzerland were investigated. Between 1 and 8 microsites of a few decimetres square, each comprising 13 to 27 thalli of X. parietina, were analysed per population. A total of 132 isolates from epiphytic and 3 isolates from epilithic specimens were investigated. Phenotypic variation was recorded among some of the thalli in the field and among sterile cultured isolates in the laboratory. A high diversity of genotypes was observed, even among thalli growing side by side in phenotypically homogenous populations. An average of 73·5%polymorphism was found in all samples. As shown with Principal Coordinates Analysis (PCO), most of the genetic variation (90%) resided within, not among, populations. As X. parietina had previously been shown with molecular and fingerprinting techniques to be homothallic, the potential genetic background of this diversity is discussed. Intense genotype rather than gene (allele) flow seems to be an important element in X. parietina populations. [ABSTRACT FROM AUTHOR]

The fine-scale genetic variation and population structure of lichen-forming fungi is little known and sampling strategies are rarely recommended or discussed. I tested if the sample sizes of molecular data sets used in recent population studies of Xanthoria parietina revealed all haplotypes potentially present and, accordingly, quantified how many haplotypes were potentially missing in the samples. Data sets were concatenated from two geographical regions in Scandinavia and investigated if the sampling reached saturation at two levels: 1) individual-based using rarefaction curves and 2) population-based using species accumulation curves. At both levels, the matrices of two molecular markers (IGS and ITS) were analysed separately. The molecular markers show similar and parallel patterns in all analyses. Rarefaction analyses did not reveal different patterns for populations in different habitats, i.e., bark and rock. Species accumulation curves estimated with the Chao 1 richness estimator indicated that 23% of the IGS and 8% of the ITS haplotypes were not detected. Corresponding figures from an abundance-based coverage estimator (ACE) were 37% and 18%. Pilot studies are recommended to determine appropriate sample sizes for genetic-based population studies of lichen-forming fungi. [ABSTRACT FROM AUTHOR]

Three new Xanthoria species are described from South Africa. Xanthoria hirsuta sp. nov. has hairs on the surface of the thallus and apothecia, best visible in young, growing parts. Dust particles and sand granules stick to this hairy surface, giving the thallus a somewhat dirty appearance. Xanthoria inflata sp. nov. has inflated lobes similar to a Menegazzia. It carries numerous crystals on its medullary hyphae, which are ivory-coloured in young, but intensely orange coloured in old lobes. Xanthoria doidgeae sp. nov. has relatively small lobes with pruinose margins. All three species are fertile, none of them forms symbiotic propagules. Xanthoparmelia perezdepazii from the Canary Islands is described as new to science. It is charactenzed by an isidiate upper surface, the presence of usnic, constipatic and protoconstipatic acids in the medulla and a brown lower surface. [ABSTRACT FROM AUTHOR]

In order to examine genetic variation and population structure of the widespread lichen-forming ascomycete Xanthoria parietina from similar habitats, but different sites in Scandinavia, we investigated seven populations in Scania, southernmost Sweden, and compared the results with a corresponding study on Storfosna, central Norway. Sequence variations of the nuclear ribosomal DNA were used as molecular markers, for both a part of the IGS region and the complete ITS1-5.8S-ITS2 region. The amount of genetic variability observed was comparable in the two investigations. Divergence between populations in different habitats found in the previous study was also present in this study. Xanthoria parietina is genetically differentiated between habitats with no evidence of restricted gene flow between populations in the same habitat at the present spatial scale, at least at sites along the coast of Scandinavia. Differentiation between habitats is considerable at both study sites, which we attribute to restricted gene flow between habitats, i.e. habitat isolation. [ABSTRACT FROM AUTHOR]

Diurnal courses of photosystem II (PS II) activity of Xanthoria elegans were continuously monitored using a novel technique of chlorophyll fluorescence imaging in the field (maritime Antarctica) over a period of 7 days. The lichen specimens grew on rock surfaces in a north-facing coastal area of Galindez Island (Argentine Islands). A portable fluorometer FluorCam equipped with a CCD camera and image analysis software was placed over a thallus so that false colour images of FV/FM and quantum yield of photochemical processes in PS II (ΦII) distribution over the thallus could be taken over the course of a day. Simultaneously, microclimatic parameters of the habitat were recorded: air and thallus temperatures, relative air humidity, PPFR (photosynthetic photon fluence rate) and global radiation. Photosynthetic processes in X. elegans were activated by rainfall or water from melting snow. After thallus hydration, FV/FM and ΦII gradually decreased from their maximum values due to evaporation and progressive loss of water from the thallus. Chlorophyll fluorescence imaging showed that the thallus dehydration started from the margins and moved towards the central thicker thallus zones. These zones exhibited higher activity of PS II than the margins throughout the day. The rate of inhibition of photosynthetic processes in PS II was faster at the margins than in the centre of the thallus. Dependence of ΦII on thallus water potential (WP) was investigated during gradual dehydration under laboratory conditions. After a decrease in WP from zero to -7 MPa, X. elegans exhibited only a 13.8% decrease in ΦII from its maximal value. Within the range of WP of from -8 to -20 MPa, the ΦII decrease was more rapid reaching the critical point (ΦII = 0) at WP of approximately -25 MPa. Chlorophyll fluorescence imaging and WP measurements showed that X. elegans is capable of maintaining detectable photosynthetic activity even at extremely low WP. Based on our microclimatological data, X. elegans may be photosynthetically active under field conditions for several hours after being wetted by rain or snowfall. It is suggested that chlorophyll fluorescence imaging is a powerful technique, transferable to field conditions and capable of visualizing heterogeneity of photosyntetic processes over a lichen thallus subjected to periodic dehydration. [ABSTRACT FROM AUTHOR]

The responses of the nitrophytic green algal lichen Xanthoria parietina to varying nitrogen CN) concentrations were investigated by collecting 67 X. parietina thalli from clay roof tiles from 13 sites in Portugal with different exposures to N. Concentrations of total N, chlorophyll α (a marker for the photobiont), ergosterol (a marker for the mycobiont), and thallus specific weight (TSW; thallus dry weight in relation to surface area) were quantified for each thallus to see how biont investments were related to thallus N concentrations. Thallus N ranged from 11 to 43 mg g-1 DW revealing a wider N concentration range in this lichen compared to other green algal lichen species. Both chlorophyll α and ergosterol concentrations increased with increasing thallus N, with a steeper increase of the photobiont marker. TSW was similar in all thalli without any significant effect of thallus N concentration, suggesting that thallus developmental patterns are similar in low and high thallus N concentrations. The relatively higher resource allocation to the photobiont in relation to the mycobiont with increasing thallus N concentrations is an indication of the capacity of X. parietina to meet the C demands associated with N assimilation. This result is also in agreement with the inter-specific resource allocation pattern for green algal lichens across the same N concentration range. [ABSTRACT FROM AUTHOR]

Specimens of Xanthoria parietina were collected from worldwide locations and ascospore discharge used to establish axenic cultures of the mycobiont. DNA was extracted and RAPD-PCR fingerprinting of 59 isolates was successfully achieved, resulting in 58 unique fingerprints. 110 multilocus RAPD markers were generated and used to construct a dendrogram. Two main groups were distinguished (75% bootstrap support): the first comprising samples from the Iberian Peninsula, the Balearic and Canary Islands; the second comprising all other worldwide samples including isolates from throughout Europe and North America. Samples from Australia and New Zealand clustered with the second group except one additional, phenotypically distinct specimen, not belonging to X. parietina, which formed an outgroup. However, comparative DNA sequence analyses are required to verify this interpretation. [ABSTRACT FROM AUTHOR]

The aim of this investigation was to determine the NH4Cl concentration threshold, above which negative physiological effects would occur in the nitrophytic lichen Xanthoria parietina. Over a 10 month period, X. parietina thalli growing on roof tiles were exposed weekly to NH4Cl concentrations of 0.04, 0.17, 0.34 or 0.69 M. Nitrogen (N) uptake from ammonium and the concentrations of total thallus N and biont markers (chlorophyll a, ergosterol and chitin) were measured on four occasions, over the experimental period. Xanthoria parietina was able to assimilate a significant quantity of the applied ammonium. However, lichens exposed to the two higher concentrations suffered damage to both the photobiont and the mycobiont, as evidenced by reduced chlorophyll a and ergosterol concentrations, while lichens exposed to the two lower concentrations showed no significant changes in either chlorophyll a or ergosterol that could be related to the ammonium inputs. Xanthoria parietina tolerated a weekly irrigation of at least 0.17 M NH4Cl, corresponding to an N deposition of c. 1000 kg ha-1 yr-1, suggesting that this species has a very high tolerance to N pollution. [ABSTRACT FROM AUTHOR]

Two new species, Xanthoria karrooensis S. Kondratyuk & Kärnefelt and Xanthoria alexanderbaai S. Kondratyuk & Kärnefelt, both apparently endemic to South Africa, are described and illustrated. Other xanthorioid species known from southern Africa are listed in a Table and a preliminary key is provided for the African species. The new species are compared with a number of presumably related species, and a Table is provided comparing the character states for the new species and related species. [Copyright &y& Elsevier]