Possible evidence for novel metabolism of nitrogen gas by a green alga

We report the isolation of a cukaryotic green alga ( Chlorella , strain WPI-2) which accumulates large stores of nitrogen (N) during growth in N-free medium and seems to incorporate¹⁴N₂, yet does not reduce acetylene to ethylene. Total N accumulation during growth on N-free medium and in gases free of combined N was measured by three methods: Kjeldahl, oxidative pyrolysis via chemiluminescence (Antek N analyzer), and Dumas (Coleman N analyzer). Increases in N ranging from 22–64%± 1% were observed. Isotope dilution studies using cells labelled with ¹⁵NO ₃- and then shifted to ¹⁴N₂ in N-free medium showed dilution of the ¹⁵N isotope by ¹⁴N from 5.67 to 5.32%± 0.05%. Using a variety of conditions, we were unable to demonstrate the reduction of acctylene to ethylene by WPI-2, although diazotrophic cyanobacteria gave positive results. Although the data on WPI-2 are not conclusive in establishing this alga as a diazotroph, the data do suggest that within the Chlorophyceae there may exist a novel form of nitrogen gas metabolism.     

Expression of a Pseudomonas aeruginosa citrate synthase gene in tobacco is not associated with either enhanced citrate accumulation or efflux

Aluminum (Al) toxicity and poor phosphorus (P) availability are factors that limit plant growth on many agricultural soils. Previous work reported that expression of a Pseudomonas aeruginosa citrate synthase gene in tobacco (Nicotiana tabacum; CSb lines) resulted in improved Al tolerance (J.M. de la Fuente, V. Ramírez-Rodríguez, J.L. Cabrera-Ponce, L. Herrera-Estrella [1997] Science 276: 1566-1568) and an enhanced ability to acquire P from alkaline soils (J. López-Bucio, O. Martínez de la Vega, A. Guevara-García, L. Herrera-Estrella [2000] Nat Biotechnol 18: 450-453). These effects were attributed to the P. aeruginosa citrate synthase increasing the biosynthesis and efflux of citrate from roots. To verify these findings we: (a) characterized citrate efflux from roots of wild-type tobacco; (b) generated tobacco lines expressing the citrate synthase gene from P. aeruginosa; and (c) analyzed selected CSb lines described above. Al stimulated citrate efflux from intact roots of wild-type tobacco and root apices were found to be responsible for most of the efflux. Despite generating transgenic tobacco lines that expressed the citrate synthase protein at up to a 100-fold greater level than the previously described CSb lines, these lines did not show increased accumulation of citrate in roots or increased Al-activated efflux of citrate from roots. Selected CSb lines, similarly, failed to show differences compared with controls in either citrate accumulation or efflux. We conclude that expression of the P. aeruginosa citrate synthase gene in plants is unlikely to be a robust and easily reproducible strategy for enhancing the Al tolerance and P-nutrition of crop and pasture species.     

Analysis of TaALMT1 traces the transmission of aluminum resistance in cultivated common wheat (Triticum aestivum L.)

Allele diversities of four markers specific to intron three, exon four and promoter regions of the aluminum (Al) resistance gene of wheat (Triticum aestivum L.) TaALMT1 were compared in 179 common wheat cultivars used in international wheat breeding programs. In wheat cultivars released during the last 93 years, six different promoter types were identified on the basis of allele size. A previous study showed that Al resistance was not associated with a particular coding allele for TaALMT1 but was correlated with blocks of repeated sequence upstream of the coding sequence. We verified the linkage between these promoter alleles and Al resistance in three doubled haploid and one intercross populations segregating for Al resistance. Molecular and pedigree analysis suggest that Al resistance in modern wheat germplasm is derived from several independent sources. Analysis of a population of 278 landraces and subspecies of wheat showed that most of the promoter alleles associated with Al resistance pre-existed in Europe, the Middle East and Asia prior to dispersal of cultivated germplasm around the world. Furthermore, several new promoter alleles were identified among the landraces surveyed. The TaALMT1 promoter alleles found within the spelt wheats were consistent with the hypothesis that these spelts arose on several independent occasions from hybridisations between non-free-threshing tetraploid wheats and Al-resistant hexaploid bread wheats. The strong correlation between Al resistance and Al-stimulated malate efflux from the root apices of 49 diverse wheat genotypes examined was consistent with the previous finding that Al resistance in wheat is conditioned primarily by malate efflux. These results demonstrate that the markers based on intron, exon and promoter regions of TaALMT1 can trace the inheritance of the Al resistance locus within wheat pedigrees and track Al resistance in breeding programmes. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Molecular characterization and mapping of ALMT1, the aluminium-tolerance gene of bread wheat (Triticum aestivum L.).

The major aluminum (Al) tolerance gene in wheat ALMT1 confers. An Al-activated efflux of malate from root apices. We determined the genomic structure of the ALMT1 gene and found it consists of 6 exons interrupted by 5 introns. Sequencing a range of wheat genotypes identified 3 alleles for ALMT1, 1 of which was identical to the ALMT1 gene from an Aegilops tauschii accession. The ALMT1 gene was mapped to chromosome 4DL using 'Chinese Spring' deletion lines, and loss of ALMT1 coincided with the loss of both Al tolerance and Al-activated malate efflux. Aluminium tolerance in each of 5 different doubled-haploid populations was found to be conditioned by a single major gene. When ALMT1 was polymorphic between the parental lines, QTL and linkage analyses indicated that ALMT1 mapped to chromosome 4DL and cosegregated with Al tolerance. In 2 populations examined, Al tolerance also segregated with a greater capacity for Al-activated malate efflux. Aluminium tolerance was not associated with a particular coding allele for ALMT1, but was significantly correlated with the relative level of ALMT1 expression. These findings suggest that the Al tolerance in a diverse range of wheat genotypes is primarily conditioned by ALMT1.     

The nuclear factor-kappaB and p53 pathways function independently in primary cells and transformed fibroblasts responding to genotoxic damage

With nuclear factor-kappaB (NF-kappaB) and p53 functions generally having disparate outcomes for cell survival and cell division, understanding how these pathways are coordinated following a common activation signal such as DNA damage has important implications for cancer therapy. Conflicting reports concerning NF-kappaB and p53 interplay in different cell line models prompted a reexamination of this issue using mouse primary thymocytes and embryonic fibroblasts, plus fibroblasts transformed by E1A12S. Here, we report that following the treatment of these cells with a range of stress stimuli, p53 and NF-kappaB were found to regulate cell cycling and survival independently.     

The ophthalmic anomalies in children with Down syndrome in Split-Dalmatian County

Our aim was to present the ophthalmic anomalies in patients with Down syndrome in Split-Dalmatia County born from 1992 until 2009 year. It was a cross-sectional study. 153 children with Down syndrome aged 0-18 years from the Split-Dalmatia County were examined. One hundred twelve participants were borne in Split, 13 in Vrgorac,16 in Makarska, 12 in Sinj. All enrolled children underwent a complete ophthalmological examination (anterior segment, ocular motility, refractive status, fundus, measuring intraocular pressure (IOP). Of 89.5% percent of responders with refractive errors, 48.1% had myopia, 35.0% had hypermetropia, astygamtism in 16.7%, 28.7% strabismus, nystagmus (8.4%), cataracts (1.3%), glaucoma (1.9%), supernumerary optic disc vessels (24.1%) and keratoconus (1.3%). Conclusion: In patients with Down syndrome the prevalence of refractive errors (myopia prevalence), as well as other ophthalmological diseases was determined.     

The role of oxidative stress after retinal laser photocoagulation in nonproliferative diabetic retinopathy

Diabetic retinopathy (DR) represents the most common chronic complication of diabetes, and it is the leading cause of new cases of blindness in patients between 20-74 years old in developed countries. Laser photocoagulation (LF) represents an efficacious approach to the treatment of DR. Oxidative factors, such as free radicals (FR), are continuously generated in aerobic organisms as a result of different metabolic processes. It is well known that oxidative stress plays a role in the development of DR. The aim of this study was to evaluate the thermal effects of the scatter retinal laser photocoagulation technique on the production of FR. A total of 90 patients were enrolled in this study. They were divided in 3 groups: 30 diabetic patients with DR, 30 diabetic patients without DR, and 30 control individuals without diabetes mellitus (DM). Full scatter retinal LF was performed in all patients with DR. We measured the concentrations of superoxide dismutase (SOD), glutathione peroxidase (GPOD), catalase, and total antioxidative status (TAS). Of the 30 DR patients, 13 showed the appearance or worsening of macular edema after LEF, whereas the other 17 patients showed no change. Thirty days after LF, improvement in visual acuity was observed, but this change was not statistically significant. The mean plasma or erythrocyte lysate concentrations of various antioxidants were significantly lower in the diabetic patients without DR compared to the individuals without DM and in the diabetic patients with DR compared to the individuals without DM; the diabetic patients with DR did not show lower concentrations of the antioxidants compared to the diabetic patients without DR. The concentrations of SOD, GPOD, catalase, and TAS were significantly lower in the diabetic patients with DR after retinal scatter LF, which could be the consequence of retinal oxidative stress caused by the LF thermal effect.