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.     

Elevated CO2 and nitrate levels increase wheat root-associated bacterial abundance and impact rhizosphere microbial community composition and function

Elevated CO₂ stimulates plant growth and affects quantity and composition of root exudates, followed by response of its microbiome. Three scenarios representing nitrate fertilization regimes: limited (30 ppm), moderate (70 ppm) and excess nitrate (100 ppm) were compared under ambient and elevated CO₂ (eCO₂, 850 ppm) to elucidate their combined effects on root-surface-associated bacterial community abundance, structure and function. Wheat root-surface-associated microbiome structure and function, as well as soil and plant properties, were highly influenced by interactions between CO₂ and nitrate levels. Relative abundance of total bacteria per plant increased at eCO₂ under excess nitrate. Elevated CO₂ significantly influenced the abundance of genes encoding enzymes, transporters and secretion systems. Proteobacteria, the largest taxonomic group in wheat roots (~ 75%), is the most influenced group by eCO₂ under all nitrate levels. Rhizobiales, Burkholderiales and Pseudomonadales are responsible for most of these functional changes. A correlation was observed among the five gene-groups whose abundance was significantly changed (secretion systems, particularly type VI secretion system, biofilm formation, pyruvate, fructose and mannose metabolism). These changes in bacterial abundance and gene functions may be the result of alteration in root exudation at eCO₂, leading to changes in bacteria colonization patterns and influencing their fitness and proliferation.Subject terms: Microbiome, Microbial ecology, Metagenomics, Microbial ecology     

Multilocus dynamics under haploid selection

 A general haploid selection model with arbitrary number of multiallelic loci and arbitrary linkage distribution is considered. The population is supposed to be panmictic. A dynamically equivalent diploid selection model is introduced. There is a position effect in this model if the original haploid selection is not multiplicative. If haploid selection is additive then the fundamental theorem is established even with an estimate for the change in the mean fitness. On this basis exponential convergence to an equilibrium is proved. As rule, the limit states are single-gamete ones. If, moreover, linkage is tight, then the single-gamete state with maximal fitness attracts the population for almost all initial states. Received 27 November 1995; received in revised form 17 January 1996     

Analysis of formin functions during cytokinesis using specific inhibitor SMIFH2

The phragmoplast separates daughter cells during cytokinesis by constructing the cell plate, which depends on interaction between cytoskeleton and membrane compartments. Proteins responsible for these interactions remain unknown, but formins can link cytoskeleton with membranes and several members of formin protein family localize to the cell plate. Progress in functional characterization of formins in cytokinesis is hindered by functional redundancies within the large formin gene family. We addressed this limitation by employing Small Molecular Inhibitor of Formin Homology 2 (SMIFH2), a small-molecule inhibitor of formins. Treatment of tobacco (Nicotiana tabacum) tissue culture cells with SMIFH2 perturbed localization of actin at the cell plate; slowed down both microtubule polymerization and phragmoplast expansion; diminished association of dynamin-related proteins with the cell plate independently of actin and microtubules; and caused cell plate swelling. Another impact of SMIFH2 was shortening of the END BINDING1b (EB1b) and EB1c comets on the growing microtubule plus ends in N. tabacum tissue culture cells and Arabidopsis thaliana cotyledon epidermis cells. The shape of the EB1 comets in the SMIFH2-treated cells resembled that of the knockdown mutant of plant Xenopus Microtubule-Associated protein of 215 kDa (XMAP215) homolog MICROTUBULE ORGANIZATION 1/GEMINI 1 (MOR1/GEM1). This outcome suggests that formins promote elongation of tubulin flares on the growing plus ends. Formins AtFH1 (A. thaliana Formin Homology 1) and AtFH8 can also interact with EB1. Besides cytokinesis, formins function in the mitotic spindle assembly and metaphase to anaphase transition. Our data suggest that during cytokinesis formins function in: (1) promoting microtubule polymerization; (2) nucleating F-actin at the cell plate; (3) retaining dynamin-related proteins at the cell plate; and (4) remodeling of the cell plate membrane.

Formins regulate phragmoplast expansion, microtubule turnover rate, actin nucleation, and cell plate membrane remodeling during cytokinesis.     

Cyclical environmental changes as a factor maintaining genetic polymorphism. 1. Two-locus haploid selection

To classify different types of cyclic selection, a measure of fitness disequilibrium was used, and a class of systems were considered where this measure has the same sign in all states (sign-concordant environments). The necessary conditions for existence of a fixed point (considering any moment within the period as a referring one) are obtained for sign-concordant systems. However, analytical study of such systems, in the case of selection for equal additive genes, and numerical testing of more general situations, allowed us to conclude that no polymorphism is possible. In the alternative class of sign-concordant systems, polymorphism is possible. However, we found that global stability is an exception rather than a rule for sign-nonconcordant systems. Massive numerical simulations of selection in a four-state environment were made for cycle lengths in the range 8–28 and with evenly distributed selection coefficients. The proportion of polymorphic regimes ranged up to about 1.5%, and was dependent on the recombination rate between the loci. It should be stressed, that polymorphism maintenance in the haploid systems, when it is possible, can not be considered as an effect derived from constant selection, or be a result of any hidden form of heterozygous advantage. In other words, polymorphism stability is causally connected with environmental fluctuations. Equally important is that this effect of fluctuations is only possible because of recombination: in single locus systems haploid cyclical selection is unable to produce protected polymorphism.     

Effects of pH and deuterium oxide on the heat-inactivation temperature of chloroplasts

The inactivation temperature for Hill activity and for the long-lived delayed fluorescence of isolated Pisum sativum L. chloroplasts was found to depend on pH, the maximal value being in the pH region 5–7. Salts increase the inactivation temperature by 4–7°C. Effects of D₂O and some other substances that modify the thermostability of chloroplasts are dependent on pH. It is concluded that thermal denaturation of proteins is the most probable mechanism for heat inactivation of chloroplasts.Abbreviations Hepes 4-(2-hydroxymethyl)-1-piperazineethane sulfonic acid - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol     

Composition and characteristics ofCandida albicans cells differing in resistance to polyene antibiotics

Development of resistance to polyene antibiotics in a highly resistantCandida albicans strain was shown to be accompanied by the complete loss of the ability to synthesize ergosterol and the substitution of other sterol components as well as by higher amounts of free fatty acids. No significant differences in lipid and protein composition have been noted between slightly resistant cultures ofC. albicans and initially susceptible ones. Sterols of resistant cultures (added in the solution and incorporated in the composition of native membranes and liposomes) have the same affinity for polyene antibiotics as do sterols of a sensitive strain. It was found that the resistance of the slightly resistantC. albicans strain did not depend on the cell wall. The ability of some detergents to reduce resistance to polyene antibiotics was shown.     

Cariniferosides A–F and other steroidal biglycosides from the starfish Asteropsis carinifera

Six new steroidal biglycosides, cariniferosides A–F (1–6), were isolated along with six previously known glycosides, 7–12, from the alcoholic extract of the starfish Asteropsis carinifera. The structures of 1–6 were determined by extensive NMR and ESIMS techniques. The isolated compounds did not show any apparent cytotoxicity in cancer cell lines HCT-116, RPMI-7951, and T-47D, but sulfated compounds 6, 11, and 12 demonstrated a significant inhibition of RPMI-7951 and T-47D cell colony formation in a soft agar clonogenic assay.