An Artificial Neural Network Model to Predict the Phenology of Early-Maturing Soybean Varieties from Climatic Factors

Biophysics - Abstract—Soybean phenology is strongly influenced by temperature and day length, and phenological records clearly reflect the changes in climatic conditions. A model including...     

Hypermutable Non-Synonymous Sites Are under Stronger Negative Selection

Mutation rate varies greatly between nucleotide sites of the human genome and depends both on the global genomic location and the local sequence context of a site. In particular, CpG context elevates the mutation rate by an order of magnitude. Mutations also vary widely in their effect on the molecular function, phenotype, and fitness. Independence of the probability of occurrence of a new mutation''s effect has been a fundamental premise in genetics. However, highly mutable contexts may be preserved by negative selection at important sites but destroyed by mutation at sites under no selection. Thus, there may be a positive correlation between the rate of mutations at a nucleotide site and the magnitude of their effect on fitness. We studied the impact of CpG context on the rate of human–chimpanzee divergence and on intrahuman nucleotide diversity at non-synonymous coding sites. We compared nucleotides that occupy identical positions within codons of identical amino acids and only differ by being within versus outside CpG context. Nucleotides within CpG context are under a stronger negative selection, as revealed by their lower, proportionally to the mutation rate, rate of evolution and nucleotide diversity. In particular, the probability of fixation of a non-synonymous transition at a CpG site is two times lower than at a CpG site. Thus, sites with different mutation rates are not necessarily selectively equivalent. This suggests that the mutation rate may complement sequence conservation as a characteristic predictive of functional importance of nucleotide sites.     

Role of proteinase inhibitors in potato protection

Mechanical damage or infection of potatoes with Phytophthora infestans caused an accumulation of only serine protease inhibitors in exudates of potato tubers. Among them, proteins prevailed that are structurally similar to those present in healthy tubers: a 22-kDa trypsin inhibitor, a 21-kDa serine protease inhibitor consisting of two polypeptide chains, and a 8-kDa potato chymotrypsin I inhibitor produced de novo. The accumulated proteins inhibited the growth of hyphae and germination of zoospores of P. infestans. Treatment with elicitors, jasmonic and arachidonic acids, intensified the accumulation of these inhibitors in tubers in response to the wound stress, whereas salicylic acid blocked this process. These results suggest that the lipoxygenase metabolism plays a substantial role in signal transduction of the protective system of resting potato tubers.     

Superunstable alleles at the cut locus in Drosophila melanogaster

Summary This is a detailed study of the reversions of the ct ^MR2 allele putatively carrying á mobile element (MR-transposon) in the cut locus. Stable, unstable and superunstable revertants have been identified. Besides, a series of multiple unstable visible and lethal ct mutations derived from the ct ^MR2 allele have been obtained. They are shown to include supermutable alleles. The results suggest that the MR-transposon is connected with at least three functions: excision; change of orientation; and change of position within the cut locus, these functions being disturbed in different ways in different unstable ct ⁺ and ct alleles. In some cases the mutant transitions are somehow strongly stimulated leading to superinstability, reaching the rate of 0.5.     

Experimental comparison of competition and facilitation in alpine communities varying in productivity

Question. Competitive and facilitative interactions among plant species in different abiotic environments potentially link productivity, vegetation structure, species composition and functional diversity. We investigated these interactions among four alpine communities along an environmental productivity gradient in a generally harsh climate. We hypothesised that the importance of competition would be higher in more productive sites. Location. Mt. M. Khatipara (43°27′N, 41°41′E, altitude 2750 m), NW Caucasus, Russia. Communities ranged from low‐productivity alpine lichen heath (ALH) and snowbed communities (SBC), to intermediate productivity Festuca grassland (FVG), and high‐productivity Geranium‐Hedysarum meadow (GHM). Methods. We quantified the relative influence of competition and facilitation on community structure by expressing biomass of target species within each natural community proportionally to biomass of the species in a “null community” with experimental release from interspecific competition by removing all other species (for 6 years). An overall index of change in community composition due to interspecific interactions was calculated as the sum of absolute or proportional differences of the component species. Results. Species responses to neighbour removal ranged from positive to neutral. There was no evidence of facilitation among the selected dominant species. As expected, competition was generally most important in the most productive alpine community (GHM). The intermediate position for low‐productivity communities of stressful environments (ALH, SBC) and the last position of intermediately productive FVG were unexpected. Conclusions. Our results appear to support the Fretwell‐Oksanen hypothesis in that competition in communities of intermediate productivity was less intense than in low‐ or high‐productive communities. However, the zero net effect of competition and facilitation in FVG might be the result of abiotic stress due to strong sun exposure and high soil temperatures after neighbour removal. Thus, non‐linear relationships between soil fertility, productivity and different abiotic stresses may also determine the balance between competition and facilitation.     

Synthesis, antiproliferative activity and genotoxicity of novel anthracene-containing aminophosphonates and a new anthracene-derived Schiff base

A new Schiff base, 9-anthrylidene-furfurylamine and three novel anthracene-containing α-aminophosphonates, [N-methyl(dimethoxyphosphonyl)-1-(9-anthryl)]-p-toluidine, [N-methyl(diethoxyphosphonyl)-1-(9-anthryl)]-p-toluidine and [N-methyl(diethoxyphosphonyl)-1-(9-anthryl)]furfurylamine were synthesized. The compounds have been characterized by elemental analysis, TLC, IR, NMR and fluorescent spectra. The aminophosphonates and their synthetic precursors were tested for in vitro antitumor activity on a panel of seven human epithelial cancer cell lines. Safety testing was performed both in vitro (3T3 NRU test) and in vivo on ICR mice for genotoxicity and antiproliferative activity. 9-Anthrylidene-furfurylamine and [N-methyl(diethoxyphosphonyl)-1-(9-anthryl)]furfurylamine were most potent cytotoxic agents towards colon carcinoma cell line HT-29. The latter compound exhibited also antiproliferative activity to HBL-100, MDA-MB-231 and 647-V cells. The aminophosphonate [N-methyl(dimethoxyphosphonyl)-1-(9-anthryl)]-p-toluidine and its synthetic precursor 9-anthrylidene-p-toluidine were found to be cytotoxic to HBL-100 and HT-29 tumor cell lines, respectively. Moderate genotoxic and antiproliferative activity in vivo and low toxicity to Balb/c 3T3 (clone 31) mouse embryo cells were observed for all tested compounds. The subcellular distribution of two tested compounds in a tumor cell culture system was also studied.     

Two-component covalent inhibitor

Inhibitors that covalently damage proteins or nucleic acids offer great potency, but are difficult to rationally design and suffer from poor specificity. Here we outline a general concept for constructing covalent inhibitors, called the two-component covalent inhibitor (TCCI). The approach takes advantage of two ligand analogs equipped with pre-reactive groups. Binding of the analogs to the adjacent sites of a target biopolymer brings the pre-reactive groups in close proximity and causes their interaction followed by covalent damage of the target. In the present study we used light-activated pre-reactive groups to inactivate a DNA polymerase. It was found that the efficiency of a traditional single-component inhibitor was greatly reduced in the presence of a non-target protein, while the TCCI was not significantly affected. Our findings suggest that TCCI approach has advantages in inactivation of biopolymers in complex multi-component systems.