Cowpea viruses: Effect of single and mixed infections on symptomatology and virus concentration

Here we investigated the nature and functional consequences of mutations in the HIV-1tat gene within an epidemiologically-linked AIDS transmission cohort consisting of a non-progressing donor (A) and two normal progressing recipients (B and C). Multiple nonsynonymous mutations in thetat first exon were observed across time in all individuals. Some mutations demonstrated striking host specificity despite the cohort being infected with a common virus. Phylogenetic segregation of thetat clones at the time of progression to AIDS was also observed especially in recipient C. Tat clones supporting high levels of transactivation were present at all time points in all individuals, although a number of clones defective for transactivation were observed for recipient C in later time points. Here we show that thetat quasispecies in a linked transmission cohort diversify and evolve independently between hosts following transmission. It supports the belief that quasispecies variation in HIV-1 is a mechanism for selection towards defining a fitter gene variant that is capable of resisting the human immune system.     

Perturbations in nucleosome structure from heavy metal association

Heavy metals have the potential to engage in strong bonding interactions and can thus function in essential as well as toxic or therapeutic capacities. We conducted crystallographic analyses of heavy cation binding to the nucleosome core particle and found that Co²⁺ and Ni²⁺ preferentially associate with the DNA major groove, in a sequence- and conformation-dependent manner. Conversely, Rb⁺ and Cs⁺ are found to bind only opportunistically to minor groove elements of the DNA, in particular at narrow AT dinucleotide sites. Furthermore, relative to Mn²⁺ the aggressive coordination of Co²⁺ and Ni²⁺ to guanine bases is observed to induce a shift in histone–DNA register around the nucleosome center by stabilizing DNA stretching over one region accompanied by expulsion of two bases at an opposing location. These ‘softer’ transition metals also associate with multiple histone protein sites, including inter-nucleosomal cross-linking, and display a proclivity for coordination to histidine. Sustained binding and the ability to induce structural perturbations at specific locations in the nucleosome may contribute to genetic and epigenetic mechanisms of carcinogenesis mediated by Co²⁺ and Ni²⁺.     

Plant indicators of alluvial soils of Central Iraq

Summary The alluvial soils of Central Iraq are occupied by 4 main vegetation types. The soils under the riverian vegetation are characterised by medium salinity and high proportions of bivalent cations. The soils occupied by arid scrub vegetation have comparatively higher contents of clay and small amounts of soluble salts. The soils of the halophytic vegetation are highly saline and main component of this is sodium chloride. The soils under the aquatic vegetation are highest in organic matter and low in salinity.     

Molecular aspects in elevation of sunflower tolerance to drought by boron and calcium foliar sprays

Sunflower (Helianthus annuus L.) hybrid Hysun 333 (black seeded) was cultivated in a greenhouse and subjected during flowering stage to drought with or without the application of boron (B) and calcium (Ca) foliar sprays alone or in combination. The results revealed that drought induced a sharp decrease in seed fresh weight, seed protein and lipid contents. Application of B and Ca combined sprays overcame the drought effects on seed weight and seed lipid contents. Catalase expression was detected as a single band for all treatments where peroxidase isozymes were increased to seven, six of them were expressed when B sprays were applied with drought indicating that B has a major role in peroxidase up-regulation under drought conditions. SDS-PAGE analysis showed differential changes in protein profile with an appearance and/or disappearance of polypeptide protein bands, some of which were concluded to be drought-related proteins. The combined sprays of B and Ca seemed to overcome the effects of drought through minimizing band alterations (disappearance and/or appearance). The DD-RT PCR showed a variation in gene expression between the control and the other treatments. Sprays of B and Ca in combination seemed to be the most effective in band up-regulation and/or down-regulation that might play a possible role in improving tolerance of sunflower to overcome the drought deleterious effects.