Structural studies of p53 inactivation by DNA-contact mutations and its rescue by suppressor mutations via alternative protein–DNA interactions

A p53 hot-spot mutation found frequently in human cancer is the replacement of R273 by histidine or cysteine residues resulting in p53 loss of function as a tumor suppressor. These mutants can be reactivated by the incorporation of second-site suppressor mutations. Here, we present high-resolution crystal structures of the p53 core domains of the cancer-related proteins, the rescued proteins and their complexes with DNA. The structures show that inactivation of p53 results from the incapacity of the mutated residues to form stabilizing interactions with the DNA backbone, and that reactivation is achieved through alternative interactions formed by the suppressor mutations. Detailed structural and computational analysis demonstrates that the rescued p53 complexes are not fully restored in terms of DNA structure and its interface with p53. Contrary to our previously studied wild-type (wt) p53-DNA complexes showing non-canonical Hoogsteen A/T base pairs of the DNA helix that lead to local minor-groove narrowing and enhanced electrostatic interactions with p53, the current structures display Watson–Crick base pairs associated with direct or water-mediated hydrogen bonds with p53 at the minor groove. These findings highlight the pivotal role played by R273 residues in supporting the unique geometry of the DNA target and its sequence-specific complex with p53.     

Realized heritability of resistance to dicrotophos in greenhouse whitefly

Realized heritability (h ²) of resistance to dicrotophos in greenhouse whitefly,Trialeurodes vaporariorum Westwood, was estimated from a laboratory selection experiment. Five generations of selection increased the LC₅₀ approximately 13-fold. Estimatedh ² of resistance to dicrotophos was 0.40 when calculated with the method of Tabashnik (1992) and 0.35 with the method of Tanaka & Noppun (1989). These results suggest that 35 to 40% of the total phenotypic variation in resistance was caused by additive genetic variation. For thirteen previously reported estimates ofh ² of insecticide resistance in other insect pests, the mean was 0.29. The relatively highh ² of dicrotophos resistance forT. vaporariorum is consistent with rapid resistance development in field populations.     

Modulation of adenylate cyclase activity by sulfated glycosaminoglycans II. Effects of mucopolysaccharides and dextran sulfate on the activity of adenylate cyclase derived from various tissues

Heparin was found to be the most potent inhibitor of rat ovarian luteinizing hormone-sensitive adenylate cyclase (I₅₀ = 2 μg/ml) when compared to other naturally occurring glycosaminoglycans. This inhinibition was also appparent when this enzyme was stimulated by follicle-stimulating hormone or prostaglandin E ₂. Heparin was also found to inhibit glucagon-sensitive rat hepatice adenylate cyclase, and the prostaglandin E₁-sensitive enzyme from rat ileum and human platelets. In contrast, heparin stimulated the dopamine sensitive adenylate cyclase from rat caudate nucleus. The sulfade polysugar dextran sulfate exerts similar effects on adenylate cyclase activity of the rat ovary was shown to inhibit hormone binding to rat ovarian plasma membrane in a manner similar to that exerted by heparin. In contrast to heparin, dextran sulfate inhibited dopamine-sensitive adenylate cyclase from rat caudate nucleus.     

Biochemical,physiological and molecular characteristics of chickpea rhizobacteria from Kurdistan province,Iran

Kurdistan province of Iran is one of the main places for producing chickpea, and there is no published research on root-nodulating bacteria of this crop. Plant samples were collected and a total of 73 Rhizobium strains were isolated from root nodules. Nodulation test was done on chickpea plants. Phenotypic characteristics of the 16 representative strains were determined based on the standard bacteriological methods. Total soluble cell protein patterns by electrophoresis approach (SDS-PAGE) showed heterogeneity among the tested rhizobia strains. Based on the phenotypic features, Rhizobium strains of three groups belong to different species of the genus Mesorhizobioum including M. ciceri and M. mediterraneum and Mesorhizobium sp. The PCR technique was employed for amplification of 16S rDNA and atpD genes. For further characterisation, amplified fragment of 16S rDNA gene from a representative strain (AK21) using primers 41F and 1488R was subjected to sequencing. Sequences were aligned by BLAST software at NCBI GenBank and results showed 99% similarity with M. mediterraneum strain BKBCF3q.     

Searching behaviour of an omnivorous predator for novel and native host plants of its herbivores: a study on arthropod colonization of eucalyptus in Brazil

Adaptation to novel host plants is a much‐studied process in arthropod herbivores, but not in their predators. This is surprising, considering the attention that has been given to the role of predators in host range expansion in herbivores; the enemy‐free space hypothesis suggests that plants may be included in the host range of herbivores because of lower predation and parasitism rates on the novel host plants. This effect can only be important if natural enemies do not follow their prey to the novel host plant, at least not immediately, thus allowing the herbivores to adapt to the novel host plant. Hence, depending on the speed with which natural enemies follow their prey to a new host plant, enemy‐free space on novel host plants may only exist for a limited period. This situation may presently be occurring in a system consisting of the herbivorous moth Thyrinteina arnobia Stoll (Lepidoptera: Geometridae) that attacks various species of Myrtaceae, such as guava (Psidium guajava L.) and jaboticaba (Myrciaria spp.), in Brazil. Since the introduction of eucalyptus (Myrtaceae) species into this country some 100 years ago, the moth has included this plant species in its host range and frequently causes outbreaks, a phenomenon that does not occur on the native host plant species. This suggests that the natural enemies that attack the herbivore on native species are not very effective on the novel host. We tested this hypothesis by studying the searching behaviour of one of the natural enemies, the omnivorous predatory bug Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae). When offered a choice between plants of the two species, the predators (originally collected in eucalyptus plantations) preferred guava to eucalyptus when both plant species were clean, infested with herbivores, or damaged by herbivores but with herbivores removed prior to the experiments. The bugs preferred herbivore‐damaged to clean guava, and showed a slight preference for damaged to clean eucalyptus. These results may explain the lack of impact of predatory arthropods on herbivore populations on eucalyptus and suggests that eucalyptus may offer an enemy‐free space for herbivores.     

Allofeeding in Arabian Babblers (Turdoides squamiceps)

Allofeeding is a common social display among adult Arabian babblers (Turdoides squamiceps). The sociology and rates of allofeeding were studied with a tame population of babblers at the Shezaf Nature Reserve in the Rift Valley, Israel. Allofeeding rate varies with the season and food availability. Experimental supplementation to the whole group or to certain individuals greatly increased the rate of allofeeding, but it did not change the social order of the interactions. The interactions were almost always unidirectional: the donor allofed an individual lower in rank. Most of the few exceptions were reciprocal allofeeding among pairs of low-ranking individuals, correlated with a change in dominance between a young male and a young female. Higher-ranking individuals sometimes interfered with allofeedings by lower-ranking ones, and receivers frequently refused to accept the food offered. Allofeeding may therefore be considered as a display of dominance. However, as dominance rank rarely changes, except in very young birds, we suggest that allofeeding interactions display the prestige of the donors, that is, the degree of dominance of one individual over the other.Electronic Supplementary Material Supplementary material is available for this article at .     

Bionomics of Phlebotomus papatasi (Diptera: Psychodidae) in an endemic focus of zoonotic cutaneous leishmaniasis in central Iran.

Following an epidemiological survey of zoonotic cutaneous leishmaniasis (ZCL) in several villages of Badrood, a rural district north of the city of Natanz, central Iran, Phlebotomus (Phlebotomus) papatasi Scopoli were found to be naturally infected with Leishmania (Leishmania) major zymodeme MON-26. Sand flies were collected and dissected biweekly from rodent burrows from May to October 2001. Leptomonad infection rates varied between 6.7% and 22.0%, being greatest in September, coinciding with peak activity of P. papatasi, two-three months before the highest incidence of ZCL human cases in November-December. The leptomonad infection rate was 1.1% of the 94 P. papatasi captured indoors. In ELISA testing of 520 P. papatasi blood meals during Sept. 2001 and Aug. 2002, the proportion giving positive reactions for human, sheep, cow, goat, rodent, and bird were 31.2%, 69.6%, 63%, 38.8%, 24.7%, and 21.8%, respectively. This report thus incriminates P. papatasi as the vector of zoonotic cutaneous leishmaniasis in this part of Iran.     

Parameters Effects Evaluation of Microbial Strengthening of Sandy Soils in Mixing Experiments Using Taguchi Methodology

The effects of experimental parameters including soil type, curing duration, inoculum size, and biomass and nutrients concentration on soil strengthening due to calcite precipitation by Sporosarcina pasteurii PTCC 1645 were investigated. The laboratory-scale mixing experiments on remolded samples were designed by the Taguchi method. Soil type proved to be the most incorporating factor, followed by curing time and nutrient concentration. The main effect and the interactions of the parameters were presented and the optimal conditions were obtained. This suggests the importance of local conditions including soil type on any future large-scale, in situ application.     

Co-limitation of potato growth by Potato Cyst Nematode (Globodera rostochiensis) and Rhizoctonia solani

Globodera rostochiensis and Rhizoctonia solani are the most important growth limiting factors influencing potato production in Iran. The effects of inoculation with Potato Cyst Nematodes (PCN) (0, 50, 75 and 100 cysts/3.5?kg soil) and R. solani (with or without inoculation) on potato growth and development were investigated in cultivars Santé and Marfona. Inoculation with R. solani induced severe damage, especially when inoculation was accompanied with high density of PCN. The damage caused by R. solani tended to increase with an increase in PCN density, especially in Marfona. In Santé, number of stems or branches per plant significantly increased by inoculation with R. solani, while in Marfona it was significantly affected either by R. solani inoculation or PCN density. In Santé, number of stolons per plant was significantly increased by PCN, but not by R. solani. In Marfona, however, the number of stolons per plant was significantly affected either by R. solani inoculation or by presence of PCN, but not affected by PCN density. The general effect of R. solani or PCN inoculation treatments on shoot, below-ground and total dry weight of potato was significant, but strongly affected by cultivar. In general, our study supports the synergistic interaction between R. solani and PCN and its moderation by the use of a resistant cultivar such as Santé.