Molecular evolution of pteridophytes and their relationship to seed plants: Evidence from complete 18S rRNA gene sequences

Complete 18S ribosomal RNA sequence data from representatives of all extant pteridophyte lineages together with RNA sequences from different seed plants were used to infer a molecular phylogeny of vascular plants that included all major land plant lineages. The molecular data indicate that lycopsids are monophyletic and are the earliest diverging group within the vascular land plants, whereasPsilotum nudum is more closely related to the seed plants than to other pteridophyte lineages. The phylogenetic trees based on maximum likelihood, parsimony and distance analyses show substantial agreement with the evolutionary relationships of land plants as interpreted from the fossil record.     

Localization of α1-adrenoceptors in rat and human hearts by immunocytochemistry

The localization of the ai adrenoceptors (₁-AR) in the heart tissues from rat and human and in the cultured heart cells from neonatal rats was studied by indirect immunofluorescence and postembedding electronmicroscopical immuno-gold technique. With antipeptide antibodies directed against the second extracellular loop of the human ₁-AR (AS sequence 192–218), this receptor was found to be localized along the sarcolemma in both human and rat hearts. Similar localization sites were detected in cultivated rat neonatal cardiomyocytes. Beside the localization in cardiomyocytes, ₁-AR were identified in endothelial cells of capillaries and smooth muscle cells of coronary vessels, in neuronal endings, in mast cells of cultivated heart cells but not, or in less amount in fibroblasts. Interestingly, in the right atrium of rat heart the localization of ₁-AR was found to be near or on atrial natriuretic factor (ANF) granules, providing the basis for the -adrenergic influence on ANF release. The immunocytochemical studies further confirm and complete the findings known by using autoradiographic binding studies with specific ligands.     

Reduction of cardiac hypertrophy in TGR(mREN2)27 by angiotensin II receptor blockade

TGR(mREN2)27 is a transgenic rat harboring the murine Ren-2 gene and exhibit fulminant hypertension and marked heart hypertrophy. In order to study the role of angiotensin II in the increase of cardiac mass, these animals were treated with anti-hypertensive and non-antihypertensive doses of the angiotensin II receptor AT₁ antagonist Telmisartan for 9 weeks. All doses led to significant reductions of heart hypertrophy detected by the evaluation of the diameter of cardiac muscle bundles. We conclude from this study that cardiac hypertrophy in TGR(mREN2)27 is characterized by an increased volume of cardiomyocytes and an unchanged amount of fibrous tissue and that angiotensin II plays an important role in the mechanisms leading to this phenotype.     

Agglutinierte Foraminiferen aus Graptolithen-Schwarzschiefern des Llanvirnium (Ordovizium) von Plettenberg im Sauerland (Nordrhein-Westfalen,NW-Deutschland)

The Plettenberger Bänderschiefer (Ordovician, Lower Llanvirnian, Zone ofDidymograptus bifidus (Hcall) from the type locality at Plettenberg (Sauerland, NW-Germany) yielded a foraminiferal fauna consisting of primitive agglutinated species (Amphitremoida, Bathysiphon,?Raibosammina, ?Thekammina, Thurammina). Forming one of the stratigraphically oldest European foraminiferal assemblages, these taxa were washed out of an unconsolidated graptolite siltstone and represent a pelagic, oxygen-depleted environment.     

Rapid reactions of spruce cells to elicitors released from the ectomycorrhizal fungus Hebeloma crustuliniforme, and inactivation of these elicitors by extracellular spruce cell enzymes

Elicitors released from hyphae or cell walls of the ectomycorrhizal fungus Hebeloma crustuliniforme (Bull. ex Fries.) Quél. induced in suspension-cultured cells of Picea abies (L.) Karst. a set of fast reactions: (i) an immediate efflux of Cl^– into the medium, followed by a K⁺ efflux; (ii) an influx of Ca²⁺ (measured as accumulation of ⁴⁵Ca²⁺ in the cells); (iii) a phosphorylation of a 63-kDa protein and dephosphorylation of a 65-kDa protein (detectable by 4 min after elicitor application); (iv) an alkalinization of the medium, and (v) a transient synthesis of H₂O₂. The removal of extracellular Ca²⁺ by EGTA delayed the elicitor-induced alkalinization. A further reduction of this response could be achieved by TMB-8 an inhibitor of Ca²⁺ release from intracellular stores. Moreover, the inhibition of protein kinase activity by staurosporine prevented the extracellular alkalinization completely. However, the effectiveness of the elicitors in inducing the extracellular alkalinization was strongly impaired by constitutively secreted enzymes of spruce cells which cleaved the elicitors to inactive fragments. It is suggested that in ectomycorrhizae the efficacy of elicitors released from fungal cell walls is controlled by apoplastic enzymes of the host; the plant itself is able to reduce the activity of fungal elicitors on their way through the plant cell wall. But those elicitors which finally reach the plasma membrane of host cells induce reactions that are similar to the early defense reactions in plant-pathogen interactions.Abbreviations DW dry weight - FW fresh weight - TMB-8 3,4,5 trimethoxybenzoic acid 8-(diethylamino)-octyl ester We thank Prof. M. Zenk (Universität München, Germany) for providing spruce cell cultures, and Dr. I. Kottke (Universität Tübingen, Germany) for isolates of Hebeloma crustuliniforme Tü 704. We are also thankful to Dr. W. Mayer (Universität Tübingen) for valuble discussions. This work was supported by Deutsche Forschungsgemeinschaft. B. Zitterell-Haid was financed by Graduiertenkolleg Interaktion in Waldökosystemen (supported by Deutsche Forschungsgemeinschaft) and G. Hebe by a scholarship of the Landesgraduiertenförderungsgesetz.     

Behavioral strategies of aphid hyperparasitoids to escape aggression by honeydew-collecting ants

We analyzed the behavioral interactions between two species of honeydew-collecting ants (Lasius niger, Myrmica laevinodis) and foraging females of four species of aphid hyperparasitoids (Aphidencyrtus aphidivorus, Dendrocerus carpenteri, Pachyneuron aphidis, Asaphes vulgaris) usingAphis fabae ssp.cirsiiacanthoidis andLysiphlebus cardui on thistles as aphid and primary parasitoid, respectively. The observed interaction patterns and foraging parameters varied within hyperparasitoid species and revealed different strategies based upon behavioral and morphological constraints.D. carpenteri generally tried to avoid ant encounters. This avoidance strategy was successful in interactions withM. laevinodis but failed when encountering the more aggressiveL. niger, which caused about 26% adult mortality. In contrast,A. aphidivorus, P. aphidis, andA. vulgaris possess jumping ability and were hardly exposed to mortality risks. The escape reaction jump off was used as soon as ants made physical contact with foraging females. While the flight strategy ofP. aphidis is connected with cryptic movement patterns without avoidance behavior,A. aphidivorus first avoided ants and jumped off only as a last resort. Similar patterns, but less expressive, are displayed byA. vulgaris. We suggest that these different strategies are responsible for different foraging success in ant-attended resources in field.     

Development of insect resistance in tomato plants expressing the δ-endotoxin gene ofBacillus thuringiensis subsp.tenebrionis

A crystal -endotoxin gene ofBacillus thuringiensis subsp.tenebrionis (B.t.t.) encoding a coleopteran insect-specific toxin was used to construct a chimeric gene which expressed the toxin in plant cells. Via anAgrobacterium tumefaciens binary vector system, the toxin gene was transferred into tomato cells. From leaf disks recombinant plants were regenerated. Hybridization experiments demonstrated that these plants synthesized toxin-specific mRNA of the expected size. Transgenic tomato plants with the chimericB.t.t. toxin gene contained a 74 kDa protein which cross-reacted with toxin antibodies. The expression caused a significant insecticidal activity of the transgenic tomato plants against Colorado potato beetle larvae.