Phytoplankton assemblages and steady state in deep and shallow eutrophic lakes – an approach to differentiate the habitat properties of Oscillatoriales

Ecological conditions and phytoplankton succession in two shallow hypertrophic lakes (Langer See and Melangsee) and a dimictic, eutrophic lake (Scharmützelsee) in a lake chain in Eastern Germany were analyzed from 1999 to 2001 in order to find situations of phytoplankton steady state assemblages and variables controlling the phytoplankton composition according to Reynolds et al. (2002). Long term background data from 1993 to 2001 suggest steady state conditions in shallow lakes, whereas the deep lake exhibited irregular fluctuations between various phytoplankton stages. Since the phytoplankton composition in the shallow lakes was similar in all the 3 years, it was highly predictable. Steady state conditions dominated by different species of Oscillatoriales were detected during the summer period 1999 and 2000 in Langer See and in Melangsee (see Mischke & Nixdorf, this volume). This dominant assemblage found in both lakes (group S ₁ acc. to Reynolds et al., 2002): Planktothrix agardhii (Gom.) Anagn. et Kom., Limnothrix redekei (Van Goor) Meffert, Pseudanabaena (Lauterb.) is typical in turbid mixed layers with highly light deficient conditions, but it is also regularly dominant in the dimictic lake Scharmützelsee as observed in 1999 and 2001 (Pseudanabaena limnetica (Lemm.) Kom. The Nostocales Cylindrospermopsis raciborskii (Wolz.) Seenayya et Subba Raju and Aphanizomenon gracile (Lemmerm.) Lemmerm. were important in the shallow lakes as well as in lake Scharmützelsee. Nevertheless, the occurrence of filamentous cyanobacteria in the dimictic lake was not regular and an unpredictable change in phytoplankton development was observed in 2000. It is discussed, whether this phenomenon of regular succession in shallow hypertrophic lakes is caused by adaptation to a resilient and an extreme environment or by the pool of species that can live or survive in that environment. This was checked through comparison of the depth of the mixed layer, the mean daily irradiance within this layer and the nutrient resources. Although the nutrient resources in both types of lake are near threshold levels, indicating growth inhibition by dissolved nutrients (DIP, DIN, TIC, DSi), the under water light supply seems to be the key factor favoring the dominance of filamentous cyanobacteria belonging to the functional group S ₁.     

Equilibrium phase conditions in shallow German lakes: How Cyanoprokaryota species establish a steady state phase in late summer

In 2000, a field study in two shallow, polytrophic lakes (Langer See and Melangsee) in eastern Germany revealed an equilibrium state assemblage of Cyanoprokaryota in late summer. During 4 successive weeks in Langer See Planktothrix agardhii (Gom.) Anagn. et Kom., Aphanizomenon gracile (Lemmerm.) Lemmerm. and Pseudanabaena limnetica Lemmerm. were more than 80% of the standing biomass of phytoplankton, and their cumulative biovolume was around 33 mm³ l^?1 ((±3.2 SD). In Melangsee, the very small Limnothrix species L. amphigranulata (Van Goor) Meffert was the most common species, accompanied by Pseudanabaena limnetica and Planktothrix agardhii. For 3 weeks, their cumulative biovolume was about 23 mm³ l^?1 ((±3.4 SD), which represented 75 – 82% of total biovolume. The dominant species all belong to the functional group S1 defined by Reynolds (1997), except for A. gracile, which we suggest to be included in group S _N. In both lakes mean light intensities ranged between 2.2 and 8.3 E m^?2 d^?1. Overall species spectra were very similar in both lakes, but dominance by Limnothrix and by Planktothrix in the respective lakes is observed repeatedly. The success of these species is discussed in the context of the habitat properties in August/September. Summer mixing events represented no disturbances in the sense of Connell (1978), since they do not interrupt the species dominance. More frequent mixing events and higher concentrations of dissolved nitrogen occurred in Langer See than in the more shallow, but wind protected Melangsee. In Langer See light deficient conditions were intensified by an increasing biomass of P. agardhii, and this species probably benefited from nutrient input by more frequent resuspension. The light deficiency also affected the diversity, expressed as Shannon–Wiener Index (H), which was reduced more in lake Langer See (H = 0.51) than in Melangsee (0.74) during steady state periods. Recognizing the important effects of mixing, we suggest an additional variable to describe habitat properties: the number of full mixing days as a proportion of total days of observation should help to discriminate between shallow habitats with intermittent mixing events, and those with more regularly mixing in summer period.     

Characterization and analysis of posttranslational modifications of the human large cytoplasmic ribosomal subunit proteins by mass spectrometry and Edman sequencing

The 60S ribosomal proteins were isolated from ribosomes of human placenta and separated by reversed phase HPLC. The fractions obtained were subjected to trypsin and Glu-C digestion and analyzed by mass fingerprinting (MALDI-TOF), MS/MS (ESI), and Edman sequencing. Forty-six large subunit proteins were found, 22 of which showed masses in accordance with the SwissProt database (June 2002) masses (proteins L6, L7, L9, L13, L15, L17, L18, L21, L22, L24, L26, L27, L30, L32, L34, L35, L36, L37, L37A, L38, L39, L41). Eleven (proteins L7, L10A, L11, L12, L13A, L23, L23A, L27A, L28, L29, and P0) resulted in mass changes that are consistent with N-terminal loss of methionine, acetylation, internal methylation, or hydroxylation. A loss of methionine without acetylation was found for protein L8 and L17. For nine proteins (L3, L4, L5, L7A, L10, L14, L19, L31, and L40), the molecular masses could not be determined. Proteins P1 and protein L3-like were not identified by the methods applied.     

Injection by various routes of melanoma antigen-associated macrophages: biodistribution and clinical effects

Patients' autologous macrophages (AM) were used as antigen-presenting cells (APC) in a vaccination protocol against malignant melanoma. AM were administered by various routes, including intralymphatic, since these cells did not express CCR7, a molecule required for APC migration to lymph nodes. Seven HLA-A2 patients with metastatic melanoma-two classified as M1 and five as M3-were included in the study. AM were produced from leukapheresis-separated mononuclear cells by 7-day culture with granulocyte-macrophage colony-stimulating factor. After separation by elutriation, AM were frozen in aliquots and subsequently thawed at monthly intervals, exposed to MAGE-3(271-279) peptide and injected subcutaneously into lymph nodes or into one peripheral lymph vessel. Intradermal tests were performed before and after treatment to determine peptide reactivity. No acute toxicity was observed following injection. One M1 patient had a 7-mm induration intradermal reaction response and was stabilized for 64 weeks. The M3 patients did not show any immunological or clinical response. In 11 patients, the biodistribution of 111In-labeled AM was investigated. There was no clear evidence that AM injected intradermally or subcutaneously left the site of injection. After injection into a lymph vessel of the foot region, scintigraphs showed five to ten popliteal and inguinocrural lymph nodes. This appeared to be the most efficient way to administer rapidly and safely large amounts of peptide-loaded APC into lymph nodes.     

Pancreatic vasopressin V1b receptors: characterization in In-R1-G9 cells and localization in human pancreas

Vasopressin (AVP) receptors present in In-R1-G9 cells, a hamster glucagon-secreting alpha-pancreatic cell line, were characterized using SSR-149415, a selective nonpeptide V1b receptor antagonist, and reference AVP compounds. Binding experiments, using [3H]AVP as a ligand, identified a single population of high-affinity binding sites. SSR-149415 competitively inhibited this binding and exhibited nanomolar and stereospecific affinity for these sites. The affinity of various AVP/oxytocin ligands confirmed a V1b binding profile. In functional studies, AVP was a potent stimulant in inducing intracellular Ca2+ increase, glucagon secretion, and cell proliferation. These effects were fully antagonized by SSR-149415 with a nanomolar potency, whereas its diasteroisomer as well as two selective V1a and V2 receptor antagonists were much less potent. Additionally, the order of potency of AVP agonists and antagonists was in agreement with V1b-mediated effects. By RT-PCR, we confirmed the presence of V1b receptor mRNA in both In-R1-G9 cells and in human pancreas. The distribution pattern of V1b receptors investigated in human pancreas by immunohistochemistry showed strong labeling in islets of Langerhans, and colocalization studies indicated that this receptor was expressed in alpha-glucagon, beta-insulin, and somatostatin pancreatic cells. Thus, in In-R1-G9 cells, AVP mediates intracellular Ca2+ increase, glucagon secretion, and cell proliferation by activating V1b receptors, and these effects are potently antagonized by SSR-149415. Moreover, the presence of V1b receptors also found in human Langerhans islets could suggest hormonal control of AVP in human pancreas.     

A new Arabidopsis thaliana mutant deficient in the expression of O-methyltransferase impacts lignins and sinapoyl esters

A promoter-trap screen allowed us to identify an Arabidopsis line expressing GUS in the root vascular tissues. T-DNA border sequencing showed that the line was mutated in the caffeic acid O-methyltransferase 1 gene (AtOMT1) and therefore deficient in OMT1 activity. Atomt1 is a knockout mutant and the expression profile of the AtOMT1 gene has been determined as well as the consequences of the mutation on lignins, on soluble phenolics, on cell wall digestibility, and on the expression of the genes involved in monolignol biosynthesis. In this mutant and relative to the wild type, lignins lack syringyl (S) units and contain more 5-hydroxyguaiacyl units (5-OH-G), the precursors of S-units. The sinapoyl ester pool is modified with a two-fold reduction of sinapoyl-malate in the leaves and stems of mature plants as well as in seedlings. In addition, LC-MS analysis of the soluble phenolics extracted from the seedlings reveals the occurrence of unusual derivatives assigned to 5-OH-feruloyl malate and to 5-OH-feruloyl glucose. Therefore, AtOMT1 enzymatic activity appears to be involved not only in lignin formation but also in the biosynthesis of sinapate esters. In addition, a deregulation of other monolignol biosynthetic gene expression can be observed in the Atomt1 mutant. A poplar cDNA encoding a caffeic acid OMT (PtOMT1) was successfully used to complement the Atomt1 mutant and restored both the level of S units and of sinapate esters to the control level. However, the over-expression of PtOMT1 in wild-type Arabidopsis did not increase the S-lignin content, suggesting that OMT is not a limiting enzyme for S-unit biosynthesis.these authors contributed equally to this workthese authors contributed equally to this work     

Identification and characterization of the last two unknown genes,dapC and dapF,in the succinylase branch of the L-lysine biosynthesis of Corynebacterium glutamicum

The inspection of the complete genome sequence of Corynebacterium glutamicum ATCC 13032 led to the identification of dapC and dapF, the last two unknown genes of the succinylase branch of the L-lysine biosynthesis. The deduced DapF protein of C. glutamicum is characterized by a two-domain structure and a conserved diaminopimelate (DAP) epimerase signature. Overexpression of dapF resulted in an 8-fold increase of the specific epimerase activity. A defined deletion in the dapF gene led to a reduced growth of C. glutamicum in a medium with excess carbon but limited ammonium availability. The predicted DapC protein of C. glutamicum shared 29% identical amino acids with DapC from Bordetella pertussis, the only enzymatically characterized N-succinyl-aminoketopimelate aminotransferase. Overexpression of the dapC gene in C. glutamicum resulted in a 9-fold increase of the specific aminotransferase activity. A C. glutamicum mutant with deleted dapC showed normal growth characteristics with excess carbon and limited ammonium. Even a mutation of the two genes dapC and ddh, interrupting both branches of the split pathway, could be established in C. glutamicum. Overexpression of the dapF or the dapC gene in an industrial C. glutamicum strain resulted in an increased L-lysine production, indicating that both genes might be relevant targets for the development of improved production strains.     

Insecticidal pyrido[1,2-a]azepine alkaloids and related derivatives from Stemona species

Eight new alkaloids, the pyrido[1,2-a]azepines stemokerrin, methoxystemokerrin-N-oxide, oxystemokerrin, oxystemokerrin-N-oxide, and pyridostemin, along with the pyrrolo[1,2-a]azepines dehydroprotostemonine, oxyprotostemonine, and stemocochinin were isolated from four Stemona species together with the known compounds protostemonine, stemofoline, 2'-hydroxystemofoline, and parvistemonine. Their structures were elucidated by 1H and 13C NMR including 2D methods and two key compounds additionally by X-ray diffraction. Besides the formation of a six membered piperidine ring, additional oxygen bridges and N-oxides contributed to structural diversity. The co-occurrence of pyrrolo- and pyridoazepines suggested biosynthetic connections starting from more widespread protostemonine type precursors. Bioassays with lipophilic crude extracts against Spodoptera littoralis displayed very strong insecticidal activity for the roots of S. curtisii and S. cochinchinensis, moderate activity for S. kerrii, but only weak effects for the unidentified species HG 915. The insect toxicity was mainly caused by the accumulation of stemofoline, oxystemokerrin, and dehydroprotostemonine displaying two different modes of action. Based on the various insecticidal activities of 13 derivatives structure-activity relationships became apparent.     

Down-regulation of the<Emphasis Type="Italic"> AtCCR1</Emphasis> gene in<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis>: effects on phenotype,lignins and cell wall degradability

Cinnamoyl CoA reductase (CCR; EC 1.2.1.44) is the first enzyme specific to the biosynthetic pathway leading to monolignols. Arabidopsis thaliana (L.) Heynh. plants transformed with a vector containing a full-length AtCCR1 cDNA in an antisense orientation were obtained and characterized. The most severely down-regulated homozygous plants showed drastic alterations to their phenotypical features. These plants had a 50% decrease in lignin content accompanied by changes in lignin composition and structure, with incorporation of ferulic acid into the cell wall. Microscopic analyses coupled with immunolabelling revealed a decrease in lignin deposition in normally lignified tissues and a dramatic loosening of the secondary cell wall of interfascicular fibers and vessels. Evaluation of in vitro digestibility demonstrated an increase in the enzymatic degradability of these transgenic lines. In addition, culture conditions were shown to play a substantial role in lignin level and structure in the wild type and in the effects of AtCCR1 repression efficiency.     

Mapping osmotic adjustment in an advanced back-cross inbred population of rice

Osmotic adjustment is one of several characters putatively associated with drought tolerance in rice. Indica cultivars are known to have a greater capacity for osmotic adjustment than japonica cultivars. We developed an advanced back-cross population using an indica donor, IR62266-42-6-2, to introgress osmotic adjustment into an elite japonica cultivar, IR60080-46A. One hundred and fifty BC₃F₃ families were genotyped using microsatellites and RFLP markers, and a few candidate genes. We evaluated osmotic adjustment in these lines under greenhouse conditions using the re-hydration technique. Using the composite interval mapping technique, we detected 14 QTLs located on chromosomes 1, 2, 3, 4, 5, 7, 8 and 10 that together explained 58% of the phenotypic variability. Most, but not all, of the alleles with positive effects came from the donor parent. On chromosome 8, two QTLs were associated in repulsion. The QTL locations were in good agreement with previous studies on this trait on rice and in other cereals. Some BC₃F₃ lines carried the favorable alleles at the two markers flanking up to four QTLs. Intercrossing these lines followed by marker-aided selection in their progenies will be necessary to recover lines with levels of osmotic adjustment equal to the donor parent. The advanced back-cross strategy appeared to be an appropriate method to accelerate the process of introgressing interesting traits into elite material.Communicated by Q. Zhang