Structure and putative function of NFX1-like proteins in plants.

The human NFX1 transcription factor constitutes a group of NFX1-type zinc finger proteins. It forms a central Cys-rich region with several NFX1-type zinc finger domains that have been shown to mediate DNA binding. Proteins with NFX1-type zinc fingers are found in protists, fungi, animals and plants, and may be ubiquitous in eukaryotes. This review discusses the structure and putative roles of NFX1-like proteins, with a focus on human NFX1 and Arabidopsis NFXL1 proteins. By means of manual sequence analysis and application of hidden Markov models, we demonstrate that NFX1-like proteins form a specific RING finger motif with a C(4)HC(3) Zn ligand signature and additional distinct features, suggesting that these proteins function as E3 ubiquitin ligases. Phylogenetic analysis revealed different clades of NFX1-like proteins. The plant proteins group into two distinct clades. The genomes of plants such as rice, Arabidopsis, poplar and grapevine encode one member of each clade, suggesting that the presence of two NFX1-like factors is sufficient in flowering plants. The Arabidopsis proteins presumably fine-tune opposed biotic and abiotic stress response pathways.

Molecular analysis of brassinosteroid action.

Brassinosteroids (BRs) are steroidal plant hormones with important regulatory roles in various physiological processes, including growth, xylem differentiation, disease resistance, and stress tolerance. Several components of the BR signal transduction pathway have been identified. The extracellular domains of receptor kinases such as BRI1 perceive BRs and transduce the signal via intracellular kinase domains. Within the cell further kinases and phosphatases determine the phosphorylation status of transcription factors such as BES1 and BZR1. These factors mediate major BR effects. Studies of BR-regulated genes shed light on the molecular mode of BR action. Genes encoding cell-wall-modifying enzymes, enzymes of the BR biosynthetic pathway, transcription factors, and proteins involved in primary and secondary metabolism are subject to BR-regulation. Gene expression data also point at interactions with other phytohormones and a role of BR in stress responses. This article gives a survey of the BR-signaling pathway. Two BR-responsive genes, OPR3 and EXO, are described in detail.

Brassinosteroid-promoted growth.

Brassinosteroids (BRs) are highly potent growth-promoting sterol derivatives. BR-deficient or BR-insensitive mutants display dwarfism. Whole plants and excised tissues have been used to analyse the mechanisms involved in BR-promoted growth. BR stimulates cell elongation and cell division, and BR has specific effects on differentiation. Underlying physiological pathways include modification of cell wall properties, effects on carbohydrate assimilation and allocation, and control of aquaporin activities. BR apparently coordinates and integrates diverse processes required for growth, partly via interactions with other phytohormones setting the frame for BR responses. Ultimately, BR-promoted growth is mediated through genomic pathways. Positive regulators of the BR response (such as BZR1 and BES1) and putative downstream components (such as EXO) are involved in the regulation of BR-responsive genes and growth promotion. BR-responsive genes have been identified in several plant species. However, causal links between physiological effects and changes of transcript patterns, for the most part, are still unresolved. This review focuses on physiology and molecular mechanisms underlying BR-promoted growth in the different plant organs. Interactions with other phytohormones are discussed.

Establishment of a high-efficiency SNP-based framework marker set for Arabidopsis.

The major goal of this project was the establishment of a tool for rapid mapping of new mutations and genotyping in Arabidopsis consisting of at least 100 evenly spaced framework markers. We assembled a single nucleotide polymorphism (SNP)-based marker set consisting of 112 polymorphic sites with average spacing of 1.15 Mbp derived from an SNP database that we recently developed. This information was used to set up efficient SNP detection reactions based on multiplexed primer extension assays. The 112 Columbia (Col-0)/C24 framework markers were used to assemble 18 multiplexed SNaPshot assays with which up to eight separate loci can be genotyped in a single-tube/single-capillary format. In addition, for 110 framework markers matrix-assisted laser desorption/ionization time of flight (MALDI-ToF) assays have been established for high throughput analyses. We demonstrated the usefulness and the robustness of both procedures of this tool by genotyping 48 BC3F1 individuals created between the accessions Col-0 and C24. Subsets of 10-62 of the established markers discriminate between various combinations of the accessions Col-0, C24, Landsberg erecta (Ler), Cape Verdi Islands (Cvi) and Niederzenz (Nd). Using a subset of 17 evenly distributed and established SNP markers that are also polymorphic between Ler and Col-0, we were able to rapidly map a mutant gene (tbr1) to an interval of 2.3 Mbp in an Ler (tbr1) x Col-0 cross.

[Incidence and clinical characteristics of renal insufficiency in diabetic patients]. / Inzidenz und klinische Charakteristika von Niereninsuffizienz bei Diabetikern.

BACKGROUND: In all Western countries there is a dramatic increase of diabetic patients who need renal replacement therapy. Very different figures for incidence and prevalence have been reported. There is a strong suspicion that the epidemiological dimension of the problem has been underestimated in many of the statistics. METHODS: In a retrospective analysis we assessed all patients admitted to the Department Internal Medicine Heidelberg from January 1(st) 1998 - December 31(st), 2000 for renal replacement therapy, i. e. hemodialysis or CAPD, because of acute or chronic renal failure. We counted the number of known diabetic patients (i) with signs of classical diabetic nephropathy (enlarged kidneys, proteinuria > 1g/24h +/- retinopathy), (ii) with atypical renal changes (contracted kidneys, proteinuria < 1 g/24 h) and (iii) diabetic patients with (coincident) primary chronic renal disease as well as (iv) the proportion of patients in whom the diagnosis of diabetes had been unknown when uremia had supervened. RESULTS: Dialysis treatment was started in 568 patients for acute (ARF; n = 341) or chronic (CRF; n = 227) renal failure. 95/341 (28 %) patients with ARF had diabetes. ARF occured in no less than 12/95 (13 %) of the diabetic patients after cardiological intervention. Diabetes was present in 111/227 patients with CRF (7 type 1, 104 type 2); in 12/111 patients the diagnosis of diabetes was established only after admission. Only 67/111 of the diabetic patients (60 %) had classical signs of diabetic nephropathy, in 14/111 (13 %) patients the classical signs of diabetic nephropathy were absent and in 30/111 (27 %) non-diabetic primary chronic renal disease was present. CONCLUSION: The study illustrates the importance of diabetes for the epidemiology of renal failure. A sizeable proportion of patients with acute renal failure have diabetes, typically patients with pre-existing nephropathy in whom this complication supervenes during diagnosis and treatment of late diabetic complications. In diabetic patients with chronic renal failure the presentation is frequently atypical and non-diabetic primary renal disease is present more frequently than expected by chance. In a sizeable proportion of patients diabetes had not been diagnosed by the time chronic renal failure occurred.

Brassinosteroid signaling in plants.

In animals and humans, steroid hormones (SHs) regulate gene transcription via the binding of nuclear receptors. In addition, rapid nongenomic effects of steroids occur and appear to be mediated by plasma-membrane receptors. Plants also use steroids as signaling molecules. These brassinosteroids (BRs) show structural similarity to the SHs of vertebrates and insects. Plant mutants defective in brassinosteroid biosynthesis or perception exhibit dwarfism and reduced fertility, and reveal the need for BRs during growth and development. BR signaling in Arabidopsis thaliana and rice (Oryza sativa) - dicotyledonous and monocotyledonous models, respectively - is mediated by the receptor kinases BRI1 and OsBRI1. The extracellular domain of BRI1 perceives BRs and the signal is mediated via an intracellular kinase domain that autophosphorylates Ser and Thr residues and apparently has the potential to phosphorylate other substrates. BRI1 transduces steroid signals across the plasma membrane and mediates genomic effects.

The Arabidopsis PHD-finger protein SHL is required for proper development and fertility.

The SHL gene from Arabidopsis thaliana encodes a small nuclear protein that contains a BAH domain and a PHD finger. Both domains are found in numerous (putative) transcriptional regulators and chromatin-remodeling factors. Different sets of transgenic lines were established to analyze the physiological relevance of SHL. SHL expression driven by the CaMV 35S promoter results in reduced growth, early flowering, early senescence, and impaired flower and seed formation. Antisense inhibition of SHL expression gives rise to dwarfism and delayed development. In-frame N-terminal fusion of the SHL protein to beta-glucuronidase (GUS) directs GUS to the nucleus of stably transformed Arabidopsis plants. Thus, SHL encodes a novel putative regulator of gene expression, which directly or indirectly influences a broad range of developmental processes.

Experimental heart failure in rats: effects on cardiovascular circadian rhythms and on myocardial beta-adrenergic signaling.

OBJECTIVES: Patients with chronic heart failure frequently show blunted circadian blood pressure profiles. The mechanisms involved in the loss of physiological day-night variation are still unclear, but a continuously active sympathetic nervous system could play a role. The present study evaluated long-term consequences of rat heart failure on cardiovascular circadian patterns in vivo, and on density and function of cardiac beta-adrenoceptor subtypes in vitro, as a marker of cardiac adrenergic drive. METHODS: Heart failure in rats was induced by coronary artery ligation leading to infarct sizes of >30% of left ventricular circumference. Blood pressure and heart rate were monitored for 10 weeks after infarction using radiotelemetry. Density and function of cardiac beta(1) and beta(2)-adrenoceptors were measured by radioligand binding and adenylyl cyclase stimulation. RESULTS: During the activity period at night blood pressure and heart rate were lower in rats with heart failure than in sham controls, leading to reduced night-day variation in the heart failure group. Depression of circadian rhythmicity in blood pressure was found over the whole study period, while that in heart rate occurred with a lag-time of several weeks. In failing left ventricles beta-adrenoceptors showed reduced high affinity agonist binding, a shift in the beta(1):beta(2) ratio towards the beta(2)-subtype, and decreased beta(1)-adrenergic stimulation of adenylyl cyclase. In right ventricles no differences were found between failing and control rats. The blunted nocturnal increase in blood pressure and heart rate as well as beta(1)-adrenergic desensitization were correlated with the severity of left ventricular dysfunction. CONCLUSIONS: Heart failure in rats leads to disturbed circadian patterns in blood pressure and heart rate, and to desensitization of cardiac beta(1)-adrenoceptors, indicating chronic sympathetic overactivity.

12-Oxophytodienoate reductase 3 (OPR3) is the isoenzyme involved in jasmonate biosynthesis.

In addition to OPR1 and OPR2, two isoenzymes of 12-oxophytodienoate reductase, a third isoform (OPR3) has recently been identified in Arabidopsis thaliana (L.) Heynh. The expression of the OPR3 gene is induced not only by a variety of stimuli, such as touch, wind, wounding, UV-light and application of detergent, but also by brassinosteroids. The three enzymes were expressed in a functional form in Escherichia coli, and OPR2 was additionally expressed in insect cell cultures and overexpressed in A. thaliana. Substrate conversion was analyzed using a stereospecific assay. The results show that OPR3 effectively converts the natural (9S,13S)-12-oxophytodienoic acid [Km = 35 microM, Vmax 53.7 nkat (mg protein)-1] to the corresponding 3-2(2'(Z)-pentenyl) cyclopentane-1-octanoic acid (OPC-8:0) stereoisomer while OPR1 and OPR2 convert (9S,13S)-12-oxophytodienoic acid with greatly reduced efficiency compared to OPR3. Thus, OPR3 is the isoenzyme relevant for jasmonate biosynthesis.