Multiphasic accumulation of nutrients by plants

Seedlings of rice (Oryza sativa), soybean (Glycine max) and sour orange (Citrus aurantium) were grown for 20 to 125 days under controlled conditions in nutrient solutions wiht up to 16 different concentrations of NH⁴₊, H₂PO₄^-, K⁺, Ca²⁺, Mg²⁺ or Zn²⁺. Nutrient concentrations differed by up to 4 orders of magnitude (H₂PO₄^- and Zn²⁺) and were kept constant or within certain limits by changing solutions daily. Dry weights and concentrations of N, P, K, Ca, Mg or Zn were determined for roots and tops (or roots, stems and leaves). The relationship between tissue concentration of an element and external concentration of the corresponding nutient ion was invariably multiphasic, with phases separated by sharp breaks or jumps. The kinetics of accumulation were similar to those of short-term uptake of the same ions. Reanalysis of previously published data (including data for Mn²⁺) for other plants yielded, similarly, bi- or multiphasic isotherms for accumulation. Accumulation patterns and growth were in several instances correlated, with separate phases coinciding with regions of poverty adjustment, luxury consumption and toxicity. Implications of multiphasic kinetics of long-term nutrient accumulation for membrane properties, fluxes and regulation include: (i) Membranes and uptake mechanisms must remain relatively constant throughout the life of the plant with respect to affinities for ions and concentrations at which transitions occur. (ii) Rate-limitation occurs at the plasmalemma of the root cortical cells. (iii) Uptake is at all times under multiphasic control by the external solution.     

Genes mapping to boron tolerance QTL in barley identified by suppression subtractive hybridization

Boron tolerance is a quantitative trait controlled by multiple genes. Suppression subtractive hybridization was carried out on root cDNA from bulked boron tolerant and intolerant doubled haploid barley lines grown under moderate boron stress to identify genes associated with boron tolerance. One hundred and eleven clones representing known proteins were found to be up‐regulated in the tolerant bulk upon boron stress. Nine clones were genetically mapped to previously reported boron tolerance QTL. These include a clone identical to the boron transporter gene Bot1 and a clone coding for a bromo‐adjacent homology domain‐containing protein, mapping to the 6H boron tolerance locus and co‐segregating with reduced boron intake in a Clipper × Sahara‐3771 mapping population. A third clone mapping to the 2H QTL region encoding an S‐adenosylmethionine decarboxylase precursor was found to provide tolerance to high boron by heterologous expression. Yeast cells expressing Sahara SAMDC were able to grow on 15 mm boron solid media and maintained cellular boron concentrations at 13% lower than control cells expressing empty vector. The data suggest that an antioxidative response mechanism involving polyamines and the ascorbate–glutathione pathway in Sahara barley may provide an advantage in tolerating high soil concentrations of boron.     

Patterns of morphological evolution in the mandible of the house mouse Mus musculus (Rodentia: Muridae)

The worldwide distributed house mouse, Mus musculus, is subdivided into at least three lineages, Mus musculus musculus, Mus musculus domesticus, and Mus musculus castaneus. The subspecies occur parapatrically in a region considered to be the cradle of the species in Southern Asia (‘central region’), as well as in the rest of the world (‘peripheral region’). The morphological evolution of this species in a phylogeographical context is studied using a landmark‐based approach on mandible morphology of different populations of the three lineages. The morphological variation increases from central to peripheral regions at the population and subspecific levels, confirming a centrifugal sub‐speciation within this species. Furthermore, the outgroup comparison with sister species suggests that M. musculus musculus and populations of all subspecies inhabiting the Iranian plateau have retained a more ancestral mandible morphology, suggesting that this region may represent one of the relevant places of the origin of the species. Mus musculus castaneus, both from central and peripheral regions, is morphologically the most variable and divergent subspecies. Finally, the results obtained in the present study suggest that the independent evolution to commensalism in the three lineages is not accompanied by a convergence detectable on jaw morphology. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 635–647.     

Naturally occurring Trichogramma species in olive farms in Egypt

A survey of two-year studies (2001-2003) was carried out in two olive groves sited at two representative olive growing areas, namely Paradise Park (arid area) and Burg E1-Arab farm (semi-arid area) to monitor the frequency of endemic Trichogramma species on olive moth (Prays oleae) and jasmine moth (Palpita unionalis). The suspended host bait traps were found to be a more practical and effective tool for collecting Trichogramma wasps than the attached ones. Four naturally occurring Trichogramma species were collected for the first time in Egypt from the olive groves, where releases have never been conducted. T.bourarachae was collected exclusively from Burg El-Arab farm. It seems that this wasp species adapts well to the semi-arid area. Three species, namely T. cordubensis, T. nr.pretiosum and T. cacociae were isolated from Paradise Park farm. All of these wasps were also bred from naturally parasitized host eggs during favorable and even at unfavorable temperature conditions of June-August. However, these endemic species did not occur naturally in sufficient numbers to keep the pest populations from reaching damaging levels.The excessive usage of insecticides and the oophagous predators (e.g., ants and lacewing larvae) are some factors that affect the performance of Trichogramma wasps in olive farms.The presence of warm weather wasp strains suggests the existence of well-adapted wasp species or swains which may be appropriate candidates for the control of target pests in olive groves. Additional study is required to determine the best “habitat-specific” species/strains of Trichogramma for augmentative release of naturally occurring wasps and to incorporate them into integrated pest management programs. Efforts should be made to conserve these endemic species from oophagous predators, hot weather and insecticides.The olive and jasmine moth-larvae and pupae found under tree canopies were bred and emerged parasitoids were listed.     

New chromosome counts in the genus Cousinia and the related genus Schmalhausenia (Asteraceae, Cardueae)

Twenty chromosome counts are reported in the genus Cousinia and the monotypic genus Schmalhausenia , which are part of the Arctium group, from Armenia, Iran, Kazakhstan and Uzbekistan. Twelve are new and eight provide confirmation of scarce or disputable previous data. The correlation between karyological data, pollen type and molecular phylogeny is very close, and on this basis two main groups can be defined. One is the arctioid group, which comprises the genera Arctium and Schmalhausenia , and a small part of the genus Cousinia , with x  = 18. The other is the genus Cousinia s.s. , with a dysploid series ranging from x  = 13–11. Some considerations on the chromosomal evolution in the group are made.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Socety , 2003, 143 , 411–418.     

Dosage differential effects of permethrin impregnated into bednets on pyrethroid resistant and susceptible genotypes of the mosquito Anopheles stephensi

Abstract Effects of bednets impregnated with permethrin 200 mg and 500mg/m² on pyrethroid resistant and susceptible strains of Anopheles stephensi and their F hybrid progeny were studied, using free-flying female mosquitoes of these three genotypes, in a room with a human subject under a polyester net, having one of his arms in contact with the treated netting. Unexpectedly an apparently higher feeding rate, but lower knockdown and mortality rates, of mosquitoes were obtained for each of the three genotypes with the higher concentration of 500mg/m² compared with the lower dose of 200mg/m². At the lower dose there was 100% mortality 24 h after exposure of all three genotypes, suggesting that there would not be selection for resistance at this dose. However, at the higher dose there was significantly higher mortality of the susceptible strain than of the F hybrids, suggesting incomplete recessiveness of this resistance and that there would therefore be effective selection for resistance by this dose.
When female mosquitoes were confined in bioassay cones on treated netting, the resistant strain of An.stephensi showed significantly less irritability (scored as the time until first flight take-off) in response to each dose, as compared with the susceptible strain and F, hybrids. The higher dose provoked more irritation of each genotype; this could explain the greater knockdown and mortality rates of mosquitoes exposed to the lower dose which was less irritating and hence more effectively insecticidal. Thus a dose of 200mg/m² is preferable to 500mg/m² for malaria vector control.     

Coupling and oviposition behaviour in two macrodiplacinid libellulids–Aethriamantha rezia (Kirby) and Urothemis assignata Selys (Libellulidae: Odonata)

Coupling and oviposition behaviour were studied in two macrodiplacinid libellulids– Aethriamantha rezia (Kirby) and Urothemis assignata Selys in die Ibadan area of Nigeria. Sperm translocation occurs in both libellulids after the male has secured the female. Pre-mating tandem flight occurs prior to mating. Mating is long in A. rezia (384–716 s, mean 480) and shorter in U. assignata (69–122 s, mean 94). After mating, both libellulids rest in tandem, the duration being longer in A. rezia (25–82 s, mean 42) than in U. assignata (0–24 s, mean 11). This is followed by tandem exploration in A. rezia and later by oviposition, the male guarding the female. In U. assignata , tandem exploration is absent, but oviposition is usually in tandem. The duration of oviposition is similar in both libellulids–6 7–148 s, mean 95, in A. rezia and 63–183 m, mean 133, in U. assignata. Aethriamantha rezia oviposits mainly on Pistia stratiotes while plants utilized by U. assignata are more variable, although P. stratiotes is also preferred. The number of eggs laid per oviposition is high, averaging 435 in A. rezia and 398 in U. assignata. High population of males at water prolongs mating and oviposition in the two species. The ecological habitats of both overlap.     

A microRNA signature associated with chondrogenic lineage commitment

Generating appropriate cartilage for clinical applications to heal skeletal tissue loss is a major health concern. In this regard, cell-based approaches offer a potential therapeutic strategy for cartilage repair, although little is known about the precise mechanism of chondrogenesis. Unrestricted somatic stem cell (USSC) is considered as a suitable candidate because of its potential for differentiating into multiple cell types. Recent studies show that microRNAs (miRNAs) are involved in several biological processes including development and differentiation. To identify the chondro-specific miRNA signature, miRNA patterns of USSCs and differentiated chondrocytes were investigated using microarrays and validation by qPCR. Prior to these analyses, chondrogenic commitment of differentiated USSCs was verified by immunocytochemistry, specific staining and evaluation of some main chondrogenic marker genes. Various in silico explorations (for both putative targets and signalling pathways) and empirical analyses (miRNA transfections followed by qPCR of some chondrogenic indicators) were carried out to support our results. Transient modulation of multiple chondro-miRs (such as mir-630, mir-624 and mir-376) with chondrocyte targets (such as TGFbR, MAP3K, collagens, SMADs and cadherins) as mediators of chondrogenic signalling pathways including cell-cell interactions, TGF-beta, and MAPK signalling suggests a mechanism for genetic induction of chondrogenic differentiation. In conclusion, this research reveals more details about the allocation of USSCs into the chondrocytes through identification of miRNA signature which modulates targets and pathways required for chondrogenic lineage and could provide guidelines for future clinical treatments and anti-miRNA therapies.