Perspectives of bacterial ACC deaminase in phytoremediation

Phytoremediation of contaminated soil and water environments is regulated and coordinated by the plant root system, yet root growth is often inhibited by pollutant-induced stress. Prolific root growth could maximize rates of hyperaccumulation of inorganic contaminants or rhizodegradation of organic pollutants, and thus accelerate phytoremediation. Accelerated ethylene production in response to stress induced by contaminants is known to inhibit root growth and is considered as a major limitation in improving phytoremediation efficiency. Recent work shows that bacterial 1-aminocyclopropane-1-carboxylate (ACC) deaminase regulates ethylene levels in plants by metabolizing its precursor ACC into alpha-ketobutyric acid and ammonia. Plants inoculated with ACC deaminase bacteria or transgenic plants that express bacterial ACC deaminase genes can regulate their ethylene levels and consequently contribute to a more extensive root system. Such proliferation of roots in contaminated soil can lead to enhanced uptake of heavy metals or rhizodegradation of xenobiotics.     

Molecular analysis of V617F mutation in Janus kinase 2 gene of breast cancer patients

BackgroundBreast cancer is a multifactorial disease with the highest frequency in females. Genetic and environmental factors can cause mutation in several genes like tyrosine kinase, JAK2 gene which may initiate cancer. Molecular analysis of mutations in the JAK2 gene along with determination of environmental, clinical and haematological risk factors associated with breast cancer patients is need of hour to improve patient's healthcare. Somatic JAK2 valine-to-phenylalanine (617 codon) mutation is one of the widely prevalent mutations.MethodsBlood was collected from seventy breast cancer patients after their consent. The questionnaire included risk factors, age group, locality, number of children, tumor type, family history, time of initial diagnosis, no of cycles/month, water conditions and exposure to radiations. Molecular analysis were carried out from genomic DNA using Sanger sequencing and allele-specific PCR to check the V617F point mutation.ResultsThe breast cancer risk factors includes unfiltered water (68.57%), urban (58.57%), menopause (55.71%), family history of cancer (18.57%), tumor grades (II, 37.14% and III, 35.71%), consanguineous marriages (44.28%) and having more than 3–4 children (45.71%). Prevalence of breast cancer was higher after the age of 35 and maximum at 35–50. In allele-specific PCR of 70 patients, 25 patients were wild type (229 bp), 25 patients were with partially deleted gene (200 bp), and 20 patient had shown no or less than 40 bp size fragments. In Sanger's sequencing of 70 BC cases, 18% were found to be positive for V617F point mutation, including 6 homozygous (T/T) and 7 heterozygous (G/T) mutations at nucleotide position 1849 in exon 14 of the JAK2 gene.ConclusionsEnvironmental and clinical risk factors were associated with breast cancer which can be overcome by improving awareness of associated risks, health facilities and reducing stress.     

Analysis of kinetochore assembly and function in Caenorhabditis elegans embryos and human cells

All eukaryotes rely on multi-protein assemblies, called kinetochores, to direct the segregation of their chromosomes in mitosis. The list of known kinetochore components has been growing rapidly in the post-genomic era: in animal cells, there are presently more than 80 proteins that show either exclusive or partial localization at kinetochores during mitosis. The future challenge is to elucidate how these proteins contribute to kinetochore structure, spindle microtubule attachment, regulation of microtubule dynamics, and the detection, signaling, and correction of microtubule attachment errors. Cultured human tumor cells, especially HeLa cells, are widely used for the study of kinetochores. Recently, the experimental advantages offered by the nematode Caenorhabditis elegans have been exploited for functional analysis of kinetochore components in the first embryonic division. Here, we discuss basic methods, largely based on fluorescence imaging, to study kinetochore structure and function in these two metazoan model systems.     

Screening of soil fungi for in vitro degradation of endosulfan

Intensive use of endosulfan has resulted in contamination of soil and water environments at various sites in Pakistan. This study was conducted to isolate efficient endosulfan-degrading fungal strains from contaminated soils. Sixteen fungal strains were isolated from fifteen specific sites by employing enrichment techniques while using endosulfan as a sole sulfur source, and tested for their potential to degrade endosulfan. Among these fungal strains, Chaetosartorya stromatoides, Aspergillus terricola, and Aspergillus terreus degraded both α- and β-endosulfan upto 75% in addition to ∼20% abiotic degradation of the spiked amount (100 mg l⁻¹) in the broth within 12 days of incubation. Biodegradation of endosulfan by soil fungi was accompanied by a substantial decrease in pH of the broth from 7.0 to 3.2. The major metabolic product was endosulfan diol along with very low concentrations of endosulfan ether. Maximum biodegradation of endosulfan by these selected fungal strains was found at an initial broth pH of 6, incubation temperature of 30°C and under agitation conditions. This study indicates that the isolated strains carried efficient enzyme systems required for bioremediation of endosulfan-contaminated soil and water environments.     

Centromere identity maintained by nucleosomes assembled with histone H3 containing the CENP-A targeting domain

Active centromeres are marked by nucleosomes assembled with CENP-A, a centromere-specific histone H3 variant. The CENP-A centromere targeting domain (CATD), comprised of loop 1 and the alpha2 helix within the histone fold, is sufficient to target histone H3 to centromeres and to generate the same conformational rigidity to the initial subnucleosomal heterotetramer with histone H4 as does CENP-A. We now show in human cells and in yeast that depletion of CENP-A is lethal, but recruitment of normal levels of kinetochore proteins, centromere-generated mitotic checkpoint signaling, chromosome segregation, and viability can be rescued by histone H3 carrying the CATD. These data offer direct support for centromere identity maintained by a unique nucleosome that serves to distinguish the centromere from the rest of the chromosome.     

Perspective of plant growth promoting rhizobacteria (PGPR) containing ACC deaminase in stress agriculture

Ethylene is a gaseous plant growth hormone produced endogenously by almost all plants. It is also produced in soil through a variety of biotic and abiotic mechanisms, and plays a key role in inducing multifarious physiological changes in plants at molecular level. Apart from being a plant growth regulator, ethylene has also been established as a stress hormone. Under stress conditions like those generated by salinity, drought, waterlogging, heavy metals and pathogenicity, the endogenous production of ethylene is accelerated substantially which adversely affects the root growth and consequently the growth of the plant as a whole. Certain plant growth promoting rhizobacteria (PGPR) contain a vital enzyme, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which regulates ethylene production by metabolizing ACC (an immediate precursor of ethylene biosynthesis in higher plants) into α-ketobutyrate and ammonia. Inoculation with PGPR containing ACC deaminase activity could be helpful in sustaining plant growth and development under stress conditions by reducing stress-induced ethylene production. Lately, efforts have been made to introduce ACC deaminase genes into plants to regulate ethylene level in the plants for optimum growth, particularly under stressed conditions. In this review, the primary focus is on giving account of all aspects of PGPR containing ACC deaminase regarding alleviation of impact of both biotic and abiotic stresses onto plants and of recent trends in terms of introduction of ACC deaminase genes into plant and microbial species.     

Cell biology: Paper alert

A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in cell biology.     

Synergistic effects of drought and ascorbic acid on growth,mineral nutrients and oxidative defense system in canola (Brassica napus L.) plants

A study was conducted to find out the role of ascorbic acid (AsA) in modulating growth and different physio-biochemical attributes of canola plants under well-watered as well as water-deficit conditions. Drought stress imposed on 60 % field capacity significantly decreased the shoot and root fresh and dry weights, leaf chlorophyll contents, shoot and root P, root K⁺, and activity of CAT enzyme, while increased chlorophyll a/b contents, MDA, NPQ, leaf total phenolics, free proline and GB contents in both canola cultivars. Foliar-applied varying levels (50, 100 and 150 mg L^?1) of AsA enhanced shoot and root fresh and root dry weights, qN, NPQ, shoot and root P, AsA as well as the activity of POD enzyme particularly under drought stress conditions. Of both canola cultivars, cv. Dunkeld was higher in shoot fresh weights, ETR and F _v /F _m, MDA, proline and GB contents, and POD activity, however, cv. Cyclone in total phenolics and qN under well-watered and water-deficit conditions. Overall, the foliar-applied AsA had a positive effect, though not marked, on salt sensitive cv. Cyclone in terms of improved growth and other attributes, whereas exogenously applied AsA had a non-significant effect on relatively salt tolerant cv. Dunkeld.