Recombinant near-isogenic lines: a resource for the mendelization of heterotic QTL in maize

Although heterosis is widely exploited in agriculture, a clear understanding of its genetic bases is still elusive. This work describes the development of maize recombinant near-isogenic lines (NILs) for the mendelization of six heterotic QTL previously identified based on a maize (Zea mays L.) RIL population. The efficient and inexpensive strategy adopted to generate sets of NILs starting from QTL-specific residual heterozygous lines (RHLs) is described and validated. In particular, we produced nine pairs of recombinant NILs for all six QTL starting from RHLs F_4:5 originally obtained during the production of the RIL population mentioned above. Whenever possible, two different NIL pairs were generated for each QTL. The efficiency of this procedure was tested by analyzing two segregating populations for two of the selected heterotic QTL for plant height, yield per plant and ears per plant. Both additive and dominant effects were observed, consistently with the presence of the QTL within the introgressed regions. Refinement of QTL detection was consistent with previous observations in terms of effects and position of the considered QTL. The genetic material developed in this work represents the starting point for QTL fine mapping aimed at understanding the genetic bases of hybrid vigor in maize. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Upper petal lip colour polymorphism in <Emphasis Type="Italic">Collinsia heterophylla</Emphasis> (Plantaginaceae): genetic basis within a population and its use as a genetic marker

Understanding the genetics of a polymorphic trait is important to predict its likely evolution. In Collinsia heterophylla, the upper petal lip colour can be either be white or white with a purple band, while the lower petal lip colour is invariably purple. Because the corolla is only partly polymorphic, the polymorphism can not have evolved due to a mutation where a pigment was lost in the entire plant, which is common in other polymorphic species. In a previous study, high frequency of the purple band was found in populations with darker flowers, indicating possible selection for this trait. In this study, I determined inheritance of the colour polymorphism using two populations (one with only white morph and other with both morphs). I conducted experimental crosses within and between floral morphs to determine whether patterns of segregation in offspring conform to single-gene predictions. Data from F₁, F₂, F₃ and backcross progeny are consistent with a genetic model of one major locus with presence of the band being completely dominant, as indicated in earlier studies using distantly related populations. A novel finding in this study was that the two morphs did not show a difference in seed germination frequency or seedling survival. This trait can thus be valuable as a genetic marker. Even though more thorough ecological data are needed to understand the potential selection pressures on upper petal lip colour in C. heterophylla, its simple inheritance may indicate the possibility of fast evolutionary response to selective forces acting on this trait.     

Dietary supplementation with <Emphasis Type="Italic">Astragalus</Emphasis> polysaccharide enhances ileal digestibilities and serum concentrations of amino acids in early weaned piglets

Two experiments were conducted to evaluate the effects of dietary supplementation with Astragalus polysaccharide (APS) on growth performance, apparent ileal digestibilities (AID) of amino acids (AA), and their serum concentrations in early weaned piglets. In Exp. 1, 60 pigs were weaned at 21 days of age (BW 7.35 ± 0.23 kg) and allocated to three treatments (20 pigs/treatment), representing supplementing 0.0% (control), 0.02% colistin (antibiotic), or 0.1% APS to a corn- and soybean meal-based diet. Average daily gain (ADG), average daily feed intake (ADFI), and feed/gain ratio (F/G) were measured weekly. Blood samples were obtained from five pigs selected randomly from each treatment for the measurement of serum free AA concentrations on days 7, 14, and 28. In Exp. 2, 12 pigs were weaned at 21 day of age (BW 7.64 ± 0.71 kg), assigned to three treatment groups as in Exp. 1, and surgically fitted with a simple T-cannula at the terminal ileum. Ileal digesta samples were obtained for the measurement of AID of AA on days 7, 14 and 28. Dietary APS did not affect ADFI, but enhanced (P < 0.05) ADG by 11 and 4.4%, and improved F/G by 5.6 and 8.4%, respectively, compared with the control and antibiotic groups. Addition of APS to the diet increased AID and serum concentrations of most nutritionally essential and non-essential AA (including arginine, proline, glutamate, lysine, methionine, tryptophan, and threonine) on days 14 and 28. Circulating levels of total AA were affected by the age of pigs and treatment × time interaction. Collectively, these findings indicate that APS may ameliorate the digestive and absorptive function and regulate AA metabolism to beneficially increase the entry of dietary AA into the systemic circulation, which provide a mechanism to explain the growth-promoting effect of APS in early weaned piglets.     

Allelic discrimination of the <Emphasis Type="Italic">Restorer-of-fertility</Emphasis> gene and its inheritance in peppers (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.)

Cytoplasmic male sterility (CMS), one of the most important traits in crop breeding, is used for commercial F₁-hybrid seed production in peppers (Capsicum annuum L.). A nuclear gene, Restorer-of-fertility (Rf), can induce normal pollen production in CMS plants resulting in fertility. Since the first report of fertility restoration in peppers, various inheritance modes have been suggested, including the presence of a third haplotype of the locus. The pepper Rf gene has not been cloned, and calculated genetic distances of linked markers have varied between research groups. A more precise allelic test and additional genetic mapping are needed to accurately select recombinants for use in marker-assisted backcrossing (MAB). Therefore, the reliability and application of these markers for allelic selection of the Rf gene was tested. Two different F₂ populations, Buja and Tamna, were used for the construction of a linkage map. From these linkage groups, a new closely linked flanking marker of the Rf gene were identified. Previous allelic testing revealed the existence of a third haplotype, Rfls ⁷⁷⁰¹ , which can function as dominant (Rf) or recessive (rf). In a previous report, Rfls ⁷⁷⁰¹ was considered to be linked to unstable male sterility (MS). However, our results suggest that unstable MS was induced by a gene residing at another locus rather than by Rfls ⁷⁷⁰¹ haplotype-linked allele.     

Propofol Reduces Inflammatory Reaction and Ischemic Brain Damage in Cerebral Ischemia in Rats

Our previous studies demonstrated that inflammatory reaction and neuronal apoptosis are the most important pathological mechanisms in ischemia-induced brain damage. Propofol has been shown to attenuate ischemic brain damage via inhibiting neuronal apoptosis. The present study was performed to evaluate the effect of propofol on brain damage and inflammatory reaction in rats of focal cerebral ischemia. Sprague–Dawley rats underwent permanent middle cerebral artery occlusion, then received treatment with propofol (10 or 50 mg/kg) or vehicle after 2 h of ischemia. Neurological deficit scores, cerebral infarct size and morphological characteristic were measured 24 h after cerebral ischemia. The enzymatic activity of myeloperoxidase (MPO) was assessed 24 h after cerebral ischemia. Nuclear factor-kappa B (NF-κB) p65 expression in ischemic rat brain was detected by western blot. Cyclooxygenase-2 (COX-2) expression in ischemic rat brain was determined by immunohistochemistry. ELISA was performed to detect the serum concentration of tumor necrosis factor-α (TNF-α). Neurological deficit scores, cerebral infarct size and MPO activity were significantly reduced by propofol administration. Furthermore, expression of NF-κB, COX-2 and TNF-α were attenuated by propofol administration. Our results demonstrated that propofol (10 and 50 mg/kg) reduces inflammatory reaction and brain damage in focal cerebral ischemia in rats. Propofol exerts neuroprotection against ischemic brain damage, which might be associated with the attenuation of inflammatory reaction and the inhibition of inflammatory genes.     

Large impact of the apoplast on somatic embryogenesis in <Emphasis Type="Italic">Cyclamen persicum</Emphasis> offers possibilities for improved developmental control <Emphasis Type="Italic">in vitro</Emphasis>

Background  

Clonal propagation is highly desired especially for valuable horticultural crops. The method with the potentially highest multiplication rate is regeneration via somatic embryogenesis. However, this mode of propagation is often hampered by the occurrence of developmental aberrations and non-embryogenic callus. Therefore, the developmental process of somatic embryogenesis was analysed in the ornamental crop Cyclamen persicum by expression profiling, comparing different developmental stages of embryogenic cell cultures, zygotic vs. somatic embryos and embryogenic vs. non-embryogenic cell cultures.     

Inhibition of <Emphasis Type="Italic">Candida</Emphasis> <Emphasis Type="Italic">albicans</Emphasis> Biofilm Formation by Antimycotics Released from Modified Polydimethyl Siloxane

Unlike various disinfectants, antifungals have not been commonly incorporated so far in medical devices, such as catheters or prostheses, to prevent biofilm formation by Candida spp. In the present study, five antimycotics were added to polydimethyl siloxane (PDMS) disks via admixture (nystatin) or impregnation (trimethylsilyl-nystatin (TMS-nystatin), miconazole, tea tree oil (TTO), zinc pyrithione). Nystatin-medicated PDMS disks exhibited a concentration-dependent inhibitory effect on biofilm formation in a microtiter plate (MTP) but not in a Modified Robbins Device (MRD). This observation, together with HPLC data and agar diffusion tests, indicates that a small fraction of free nystatin is released, which kills Candida albicans cells in the limited volume of a MTP well. In contrast, biofilm inhibition amounted to more than one log unit in the MRD on disks impregnated with miconazole, TTO, and zinc pyrithione. It is hypothesized that the reduction in biofilm formation by these compounds in a flow system occurs through a contact-dependent effect.     

Polyspecific associations of <Emphasis Type="Italic">Cercopithecus campbelli</Emphasis> and <Emphasis Type="Italic">C. petaurista</Emphasis> with <Emphasis Type="Italic">C. diana</Emphasis>: what are the costs and benefits?

Polyspecific associations (PSA) are common in many African primate communities, including the diurnal primates at Taï Forest, Côte d’Ivoire. In this paper I use data on the PSA of two forest guenons, Campbell’s (Cercopithecus campbelli) and lesser spot-nosed monkeys (C. petaurista), with Diana monkeys (C. diana) and other primates to clarify interspecific relationships during 17 months including a 3-month low-fruit period. I analyzed association in relation to fruit availability and measured forest strata use for C. campbelli and C. petaurista when alone and in associations with and without C. diana. I also measured predator risk and reactions to potential predators. C. campbelli and C. petaurista had high association rates with C. diana monkeys, and fruit availability did not influence association rates. C. campbelli and C. petaurista used higher strata when in association with C. diana than when alone, but they used even higher strata when associated with other primates without C. diana. This suggested that C. diana competitively exclude C. campbelli and C. petaurista from higher strata. There were relatively large numbers of potential predators, and C. diana were usually the first callers to threatening stimuli, suggesting that antipredator benefits of association with C. diana outweighed the competitive costs. C. campbelli spent more time in association with C. diana than C. petaurista did and appeared to be more reliant on C. diana for antipredator benefits. C. petaurista were less reliant on C. diana because of a cryptic strategy and may have associated less in some months because of high chimpanzee (Pan troglodytes) presence.     

Factors affecting immobilization of heavy metals by purple nonsulfur bacteria isolated from contaminated shrimp ponds

In order to remove heavy metals (HMs) from contaminated shrimp pond at the highest concentrations found of; 0.75 mg/l Cd²⁺, 62.63 mg/l Pb²⁺, 34.60 mg/l Cu²⁺ and 58.50 mg/l Zn²⁺, two strains of purple nonsulfur bacteria isolated from shrimp ponds (NW16 and KMS24) were investigated for their ability to immobilize HMs in 3% NaCl in both microaerobic-light and aerobic-dark conditions. Based on metabolic inhibition and metabolic-dependent studies, it was concluded that both strains removed HMs using biosorption and also bioaccumulation. The efficiency of removal by both strains with both incubating conditions tested was in the order of lead (Pb) > copper (Cu) > zinc (Zn) > cadmium (Cd). Optimal conditions for removal of HMs by strain NW16 were; cells in the log phase at 4.5 mg DCW/ml, pH 6.0, and 30°C for 30 min. With microaerobic-light conditions, the relative percent removal of HMs was: Pb, 83; Cu, 59; Zn, 39; Cd, 23 and slightly more with the aerobic-dark conditions (Pb, 90; Cu, 69; Zn, 46; Cd, 28). Cells in the log phase at 5.0 mg DCW/ml, pH 5.5, and 35°C for 45 min were optimal conditions for strain KMS24 and there were no significant differences for the removal percentages of HMs with either incubating conditions (averages: Pb, 96; Cu, 75; Zn, 46; Cd, 30). The presence of Ca²⁺ and Mg²⁺ significantly decreased the removal capacity of HMs for both strains.