Organogenesis in isolated carnation plant callus tissue cultivatedin vitro

Formation of stems both in callus tissue isolated from hypocotyl and in apical meristems culture of carnation plants (Dianthus caryophyllus L. ev. “Grenadin white, yellow, scarlet red, dark red and pink”) was evokedin vitro using chemically defined medium. The rooted stems were transferred into pots and cultivated under natural conditions.     

Diversity and ecology of desmids of peat bogs in the Jizerské hory Mts

The present study focuses on diversity and ecological preferences of desmids in peat bogs in the Jizerské hory Mts (Czech Republic). Altogether 76 desmid algae taxa have been recorded at 18 sites of the study area during our investigation in 2003–2006. Taxa Actinotaenium crassiusculum (De Bary) Teiling, Hyalotheca dissiliens var. tatrica Racib., Staurastrum avicula var. subarcuatum (Wolle) West & G. S. West, S. borgeanum Schmidle, S. simonyi var. semicirculare Coesel, Staurodesmus extensus var. isthmosus (Heimerl) Coesel, S. extensus var. vulgaris (Eichler & Racib.) Croasdale and S. spencerianus (Mask.) Teiling are new for the Czech Republic. In addition, several rare and remarkable taxa were also encountered. The species richness was relatively high in comparison to similar localities in the Czech Republic. Desmid distribution was influenced by pH and conductivity. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Reptodigitus Chapmanii (Nostocales,Hapalosiphonaceae) Gen. Nov.: A Unique Nostocalean (Cyanobacteria) Genus Based on a Polyphasic Approach1

The Nostocales is a monophyletic, heterocytous lineage of cyanobacteria capable of akinete production and division in multiple planes, depending upon family-level clade. While present in a variety of ecosystems, the diversity of the Nostocales has been poorly elucidated. Due to environmentally -induced phenotypic plasticity, morphology alone is often insufficient to determine the true phylogenetic placement of these taxa. In order to bridge this gap, taxonomists now employ the polyphasic approach, combining methods such as morphological analysis, phylogenetic analysis based on DNA sequence and genetic identity based on ribosomal genes, and secondary structure of the 16S-23S ITS and 16S rRNA gene sequences, as well as ecological characterization. Using this combined approach, a new genus and species (Reptodigitus chapmanii gen. et sp. nov.) isolated from the St. Johns River (Jacksonville, Florida, USA) within the Nostocales is herein described. Phylogenetic analyses place this taxon within the Hapalosiphonaceae, sister to the clade containing Fischerella, Hapalosiphon, and Westiellopsis. The 16S-23S ITS secondary folding structure analysis also supports the erection of this new genus.     

Resistance to Bremia lactucae in natural populations of Lactuca saligna from some Middle Eastern countries and France

The results of the first detailed screening of a resistance to Bremia lactucae in naturally growing populations of Lactuca saligna are presented here. In total, 146 accessions from 25 populations of L. saligna originating in Israel (N = 136), France (N = 8), Jordan (N = 1) and Turkey (N = 1) were tested at seedling stage for their resistance to 10 highly virulent isolates (races) of B. lactucae from Lactuca sativa (DEG2, Bl:5, Bl:15, Bl:16, Bl:17, Bl:18, Bl:21, Bl:22, Bl:24 and Bl:25). Our study strongly supports the suggestion that L. saligna is indeed generally highly resistant to B. lactucae. However, our results provide evidence that at least at a seedling stage L. saligna may not be a non‐host plant for B. lactucae, as was hypothesised for approximately the last 30 years. Some accessions expressed a differential (i.e. race‐specific) response, which accords with other recently published data for this Lactuca species. Furthermore, some geographical differences in race‐specific resistance were observed, too. Tests performed at an adult‐plant stage, however, did not prove race‐specificity of the respective accessions. To summarise, what is behind the race‐specific character of the responses observed at a seedling stage is still uncertain, as is its comparability with the race‐specific resistance of some other Lactuca species such as L. sativa or L. serriola. The presence of plant stage‐dependent resistance, governed by a combined effect of different quantitative trait loci in young and adult plants of L. saligna, is discussed.     

Involvement of Y-family DNA polymerases in mutagenesis caused by oxidized nucleotides in Escherichia coli

Escherichia coli DNA polymerase IV incorporated 2-hydroxy-dATP opposite template guanine or thymine and 8-hydroxy-dGTP exclusively opposite adenine in vitro. Mutator phenotypes in sod/fur strains were substantially diminished by deletion of dinB and/or umuDC. DNA polymerases IV and V may be involved in mutagenesis caused by incorporation of the oxidized deoxynucleoside triphosphates.     

Why are there more arboreal ant species in primary than in secondary tropical forests?

1.?Species diversity of arboreal arthropods tends to increase during rainforest succession so that primary forest communities comprise more species than those from secondary vegetation, but it is not well understood why. Primary forests differ from secondary forests in a wide array of factors whose relative impacts on arthropod diversity have not yet been quantified. 2.?We assessed the effects of succession-related determinants on a keystone ecological group, arboreal ants, by conducting a complete census of 1332 ant nests from all trees with diameter at breast height?≥?5?cm occurring within two (unreplicated) 0·32-ha plots, one in primary and one in secondary lowland forest in New Guinea. Specifically, we used a novel rarefaction-based approach to match number, size distribution and taxonomic structure of trees in primary forest communities to those in secondary forest and compared the resulting numbers of ant species. 3.?In total, we recorded 80 nesting ant species from 389 trees in primary forest but only 42 species from 295 trees in secondary forest. The two habitats did not differ in the mean number of ant species per tree or in the relationship between ant diversity and tree size. However, the between-tree similarity of ant communities was higher in secondary forest than in primary forest, as was the between-tree nest site similarity, suggesting that secondary trees were more uniform in providing nesting microhabitats. 4.?Using our rarefaction method, the difference in ant species richness between two forest types was partitioned according to the effects of higher tree density (22·6%), larger tree size (15·5%) and higher taxonomic diversity of trees (14·3%) in primary than in secondary forest. The remaining difference (47·6%) was because of higher beta diversity of ant communities between primary forest trees. In contrast, difference in nest density was explained solely by difference in tree density. 5.?Our study shows that reduction in plant taxonomic diversity in secondary forests is not the main driver of the reduction in canopy ant species richness. We suggest that the majority of arboreal species losses in secondary tropical forests are attributable to simpler vegetation structure, combined with lower turnover of nesting microhabitats between trees.     

Growth form evolution and hybridization in Senecio (Asteraceae) from the high equatorial Andes

Changes in growth forms frequently accompany plant adaptive radiations, including páramo–a high‐elevation treeless habitat type of the northern Andes. We tested whether diverse group of Senecio inhabiting montane forests and páramo represented such growth form changes. We also investigated the role of Andean geography and environment in structuring genetic variation of this group. We sampled 108 populations and 28 species of Senecio (focusing on species from former genera Lasiocephalus and Culcitium) and analyzed their genetic relationships and patterns of intraspecific variation using DNA fingerprinting (AFLPs) and nuclear DNA sequences (ITS). We partitioned genetic variation into environmental and geographical components. ITS‐based phylogeny supported monophyly of a Lasiocephalus‐Culcitium clade. A grade of herbaceous alpine Senecio species subtended the Lasiocephalus‐Culcitium clade suggesting a change from the herbaceous to the woody growth form. Both ITS sequences and the AFLPs separated a group composed of the majority of páramo subshrubs from other group(s) comprising both forest and páramo species of various growth forms. These morphologically variable group(s) further split into clades encompassing both the páramo subshrubs and forest lianas, indicating independent switches among the growth forms and habitats. The finest AFLP genetic structure corresponded to morphologically delimited species except in two independent cases in which patterns of genetic variation instead reflected geography. Several morphologically variable species were genetically admixed, which suggests possible hybrid origins. Latitude and longitude accounted for 5%–8% of genetic variation in each of three AFLP groups, while the proportion of variation attributed to environment varied between 8% and 31% among them. A change from the herbaceous to the woody growth form is suggested for species of high‐elevation Andean Senecio. Independent switches between habitats and growth forms likely occurred within the group. Hybridization likely played an important role in species diversification.     

Egg morphology fails to identify nests parasitized by conspecifics in common pochard: a test based on protein fingerprinting and including female relatedness

Conspecific brood parasites lay eggs in nests of other females of the same species. A variety of methods have been developed and used to detect conspecific brood parasitism (CBP). Traditional methods may be inaccurate in detecting CBP and in revealing its true frequency. On the other hand more accurate molecular methods are expensive and time consuming. Eadie developed a method for revealing CBP based on differences in egg morphology. That method is based on Euclidean distances calculated for pairs of eggs within a clutch using standardized egg measurements (length, width and weight). We tested the applicability of this method in the common pochard Aythya ferina using nests that were identified as parasitized (39 nests) or non‐parasitized (16 nests) based on protein fingerprinting of eggs. We also analyzed whether we can distinguish between parasitic and host eggs in the nest. We found that variation in MED can be explained by parasitism but there was a huge overlap in MED between parasitized and non‐parasitized nests. MED also increased with clutch size. Using discriminant function analysis (DFA) we found that only 76.4% of nests were correctly assigned as parasitized or non‐parasitized and only 68.3% of eggs as parasitic or host eggs. Moreover we found that MED in parasitized nests increased with relatedness of the females that laid eggs in the nest. This finding was supported by positive correlation between MED and estimated relatedness in female–female pairs. Although variation in egg morphology is associated with CBP, it does not provide a reliable clue for distinguishing parasitized nests from non‐parasitized nests in common pochard.     

Molecular characterization of the Thermomonospora curvata aglA gene encoding a thermotolerant alpha-1,4-glucosidase

The cloning, sequencing and structural characterization of a gene encoding a thermostable alpha-1,4-glucosidase from Thermomonospora curvata is described. DNA sequence analysis revealed four open reading frames designated aglA, aglR, aglE and aglF. The aglA gene encodes a thermostable alpha-1,4-glucosidase from T. curvata and is situated between two genes, aglR and aglE. Genes aglA, aglE and aglF are transcribed in the same direction, while aglR is transcribed in the opposite direction. By comparing the amino acid sequence of the alpha-1,4-glucosidase from T. curvata with other alpha-glucanases, it appears that the enzyme is a member of the alpha-amylase family. The proteins of this family have an (alpha/beta)8 barrel super secondary structure. The topology of the alpha-1,4-glucosidase was predicted by computer-assisted analysis. The topology of the secondary structures of the alpha-1,4-glucosidase resembles the structure of barley alpha-amylase, but the primary structure resembles most closely the oligo-1,6-glucosidase from Bacillus cereus. Putative catalytic residues (D221, E281 and D343) and calcium binding residues (N116, E179, D191, H224 or G225) are proposed.