Response of cytokinin pool and cytokinin oxidase/dehydrogenase activity to abscisic acid exhibits organ specificity in peas

Changes in cytokinin pool and cytokinin oxidase/dehydrogenase activity (CKX EC: 1.5.99.12) in response to increasing abscisic acid (ABA) concentrations (0.5–10 μM) were assessed in the last fully expanded leaves and secondary roots of two pea (Pisum sativum) varieties with different vegetation periods. Certain organ diversity in CKX response to exogenous ABA was observed. Treatment provoked altered cytokinin pool in the aboveground parts of both studied cultivars. Specific CKX activity was influenced significantly basically in roots of the treated plants. Results suggest that ABA-mediated cytokinin pool changes are leaf-specific and involve certain root signals in which CKX activity presents an important link. This enzymatic activity most probably regulates vascular transport of active cytokinins from roots to shoots.     

Pathogenicity of six isolates of Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina, Hyphomycetes) to Perillus bioculatus (F) (Hem., Pentatomidae)

Abstract:  The two-spotted stink bug, Perillus bioculatus (F) (Hem., Pentatomidae) is considered an important predator of Colorado potato beetle egg masses and small larvae. The susceptibility of P. bioculatus second instar nymphs to six isolates of Beauveria bassiana (Balsamo) Vuillemin, which are highly pathogenic to Colorado potato beetle, was tested in the laboratory. Five isolates were highly pathogenic and caused more than 77% mortality after 8 days at a concentration of 10⁶ conidia/ml. However, isolate IPP46 showed low pathogenicity and caused only 11% mortality of nymphs. The pathogenicity of isolates was independent of their host, source or country of origin. Isolate IPP46 was tested at six different concentrations. A linear relationship between the concentration of B. bassiana and the mortality of nymphs was observed. The 50% lethal concentration (LC₅₀) value was 3.4 × 10⁷ conidia/ml. The LT₅₀ decreased with increase of conidia concentration used. The present results suggest that isolate IPP46 has good potential as a biological control agent within an integrated pest management programme.     

The tRNA A76 Hydroxyl Groups Control Partitioning of the tRNA-dependent Pre- and Post-transfer Editing Pathways in Class I tRNA Synthetase

Aminoacyl-tRNA synthetases catalyze ATP-dependent covalent coupling of cognate amino acids and tRNAs for ribosomal protein synthesis. Escherichia coli isoleucyl-tRNA synthetase (IleRS) exploits both the tRNA-dependent pre- and post-transfer editing pathways to minimize errors in translation. However, the molecular mechanisms by which tRNA^Ile organizes the synthetic site to enhance pre-transfer editing, an idiosyncratic feature of IleRS, remains elusive. Here we show that tRNA^Ile affects both the synthetic and editing reactions localized within the IleRS synthetic site. In a complex with cognate tRNA, IleRS exhibits a 10-fold faster aminoacyl-AMP hydrolysis and a 10-fold drop in amino acid affinity relative to the free enzyme. Remarkably, the specificity against non-cognate valine was not improved by the presence of tRNA in either of these processes. Instead, amino acid specificity is determined by the protein component per se, whereas the tRNA promotes catalytic performance of the synthetic site, bringing about less error-prone and kinetically optimized isoleucyl-tRNA^Ile synthesis under cellular conditions. Finally, the extent to which tRNA^Ile modulates activation and pre-transfer editing is independent of the intactness of its 3′-end. This finding decouples aminoacylation and pre-transfer editing within the IleRS synthetic site and further demonstrates that the A76 hydroxyl groups participate in post-transfer editing only. The data are consistent with a model whereby the 3′-end of the tRNA remains free to sample different positions within the IleRS·tRNA complex, whereas the fine-tuning of the synthetic site is attained via conformational rearrangement of the enzyme through the interactions with the remaining parts of the tRNA body.     

Effect of anticoagulants in vitro on the viability of lymphocytes and content of free fatty acids in plasma

Summary These authors attempted to test the effect of anticoagulants on lymphocytes viability by reproducing the procedure used for lymphocyte isolation for various immunologic tests in which blood specimens are allowed to stay at room temperature for 2 h before lymphocytes are isolated. Blood was obtained with three different anticoagulants i.e. heparin, citrate, and CPDA (citrate, phosphate, dextrose, and adenine). Plasma was lyophilized and extracted with ethanol. Dried ethanol extracts were suspended in medium (RPMI 1640+10% fetal bovine serum) and incubated with a lymphocyte cell line (MOLT-4). After 24 h of incubation the viability of cells was examined. The following death rates of the cells were observed: heparin −63±4.6% (mean±SEM), citrate −27±6.7%, and CPDA 6.2±0.6% (P<0.0005). A significant correlation was found between these results and changes in the concentrations of free fatty acids in the extracts. These results emphasize the importance of choosing the right anticoagulant when the viability of lymphocytes is obligatory.     

Effects of low temperature,genotype and culture media on in vitro androgenic answer of pepper (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.)

Anther culture is one of the most important and useful tool to create pure lines for plant breeding programs rapidly. Some pepper genotypes are recalcitrant and embryogenic frequency in anther culture is still low or reaction is not observed at all. Temperature stress (low or high) can facilitate switching the microspore to sporophyte developmental pathway. In this study, some differences were found in embryogenic reaction among the pepper genotypes and culture media variants, depending on duration of cold treatment of flower buds. Experimental results indicated that embryogenic efficiency decreased under low-temperature stress. Nevertheless, positive effect of cold pretreatment on direct embryo induction was obtained in four genotypes—cultivar Hebar, hybrid 50/01 and lines 668/02 and 1312/02. Increasing of embryogenic reaction after cold pretreatment was observed in media variants C (24 h) and MS-3 + (24 and 48 h), while on medium variant C-0 direct embryo formation was registered only after 48 h cold pretreatment. These results show that the donor genotypes have specific requirements for type and duration of temperature pretreatment and also culture media for induction of androgenesis with higher frequency.     

Losartan Improved Antioxidant Defense,Renal Function and Structure of Postischemic Hypertensive Kidney

Ischemic acute renal failure (ARF) is a highly complex disorder involving renal vasoconstriction, filtration failure, tubular obstruction, tubular backleak and generation of reactive oxygen species. Due to this complexity, the aim of our study was to explore effects of Angiotensin II type 1 receptor (AT1R) blockade on kidney structure and function, as well as oxidative stress in spontaneously hypertensive rats (SHR) after renal ischemia reperfusion injury. Experiments were performed on anaesthetized adult male SHR in the model of ARF with 40 minutes clamping the left renal artery. The right kidney was removed and 40 minutes renal ischemia was performed. Experimental groups received AT1R antagonist (Losartan) or vehicle (saline) in the femoral vein 5 minutes before, during and 175 minutes after the period of ischemia. Biochemical parameters were measured and kidney specimens were collected 24h after reperfusion. ARF significantly decreased creatinine and urea clearance, increased LDL and lipid peroxidation in plasma. Treatment with losartan induced a significant increase of creatinine and urea clearance, as well as HDL. Lipid peroxidation in plasma was decreased and catalase enzyme activity in erythrocytes was increased after losartan treatment. Losartan reduced cortico-medullary necrosis and tubular dilatation in the kidney. High expression of pro-apoptotic Bax protein in the injured kidney was downregulated after losartan treatment. Our results reveal that angiotensin II (via AT1R) mediates the most postischemic injuries in hypertensive kidney through oxidative stress enhancement. Therefore, blockade of AT1R may have beneficial effects in hypertensive patients who have developed ARF.     

Three Novel <Emphasis Type="Italic">NF1</Emphasis> Gene Mutations in a Cohort of Bulgarian Neurofibromatoses Patients

Neurofibromatosis (NF) is a clinically heterogeneous autosomal dominant disorder. Three distinct forms have been identified: neurofibromatosis type 1 (NF1), type 2 (NF2) and schwannomatosis. In the present study, we report clinical and genetic findings in the NF1 and NF2 genes in a cohort of 27 Bulgarian patients, with 18 cases (67%) genetically verified. Both NF1 and NF2 genes were screened by Sanger sequencing on DNA samples. The Sanger negative samples were screened by Multiplex Ligation-dependent Probe Amplification (MLPA) for deletions and duplications. The results from genetic testing revealed three novel mutations and fifteen previously reported ones (13 in the NF1 gene and 2 in the NF2 gene). The novel variants in the NF1 gene are a splice site mutation c.4725-1G>A, a small deletion of five bases c.823delATCTT, p.Leu275ValfsTer14, and a single base duplication c.6547dupC, p.Arg2183ProfsTer11. The novel splice site mutation is manifested by multiple “café au lait” macules and neurofibromas. Both novel out of frame mutations were found in patients with multiple “café au lait” spots and focal epilepsy. A segmental neurofibromatosis (SNF1) is restricted to one or more body segments. Here we present a case with SNF1 caused by a somatic deletion of exons 1 to 12 of the NF1 gene which is manifested by multiple neurofibromas in the right hand. Two nonsense mutations are found in the NF2 gene. Our study adds three novel mutations to the NF1 mutation spectra and contributes to the clinical-genetic NF1-characterization. Here we report strikingly different phenotypic spectra caused by the same mutation in a single family. Our findings contribute to the genotype- phenotype correlations which are difficult to establish, due to the extremely complex NF phenotype being a combination of clinical features.     

Influence of cytokinins and novel cytokinin antagonists on the senescence of detached leaves of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Cytokinins N⁶-benzyladenine (BA) and 1-(2-chloropyridin-4-yl)-3-phenylurea (4PU-30) delayed the senescence of detached leaves (3^rd to 7^th leaf node) of wild and ethylene insensitive eti5 mutant of Arabidopsis thaliana. The novel anticytokinins, structural analogues of purine and phenylurea cytokinins also affected the senescence of detached rosette leaves of A. thaliana. They diminished to a significant extent the cytokinin-induced delay of chlorophyll destruction, but without a considerable difference in their action against both types of cytokinins. These results correlated with changes observed in ribonuclease (RNase) activity.