Do rice hybrids have heterosis for insect resistance? A study with Nilaparvata lugens (Hemiptera: Delphacidae) and Marasmia patnalis (Lepidoptera: Pyralidae)

Antibiosis-based resistance to two insect pests of rice, Nilaparvata lugens (St?l) (Hemiptera: Delphacidae) and Marasmia patnalis Bradley (Lepidoptera: Pyralidae), was compared in 11 F1 hybrids and their parental lines. Our objective was to determine whether hybrids show heterosis (hybrid vigor) for insect resistance or susceptibility. Heterosis is defined as the amount by which a hybrid exceeds its midparent value or its better parent. Overall, we did not find evidence of heterosis or heterobeltiosis (a type of heterosis in which a hybrid exceeds its better parent) for antibiosis-based resistance or susceptibility to either of the insects. One hybrid, IR64616H, seemed more resistant to M. patnalis than its better parent but none of the other hybrids showed heterobeltiosis for resistance or susceptibility to either insect. Three hybrids had resistance to N. lugens that exceeded their midparent value, possibly due to dominant resistance in one of the parents. The increased frequency and severity of insect outbreaks on hybrid rice that have been reported in China may be attributable to factors other than diminished antibiosis in hybrids, such as greater attractiveness of hybrids to migrating or dispersing insects or differences in agronomic practices applied to hybrids and inbred rice cultivars.     

Effects of GNA transgenic sugarcane on life history parameters of Parallorhogas pyralophagus (Marsh) (Hymenoptera: Braconidae), a parasitoid of Mexican rice borer

Parallorhogas pyralophagus (Marsh) is the principal parasitoid of the Mexican rice borer [Eoreuma loftini (Dyar)], the primary pest of sugarcane in south Texas. Insect resistant transgenic sugarcane producing Galanthus nivalis agglutinin (GNA) was developed to improve control of E. loftini. The present laboratory study addressed whether over two consecutive generations transgenic sugarcane delivered via artificial diet has adverse host-mediated effects on P. pyralophagus life history parameters. The results of this study showed that a number of life history parameters were affected by transgenic sugarcane, whereas others were not affected, and that effects varied between generations. In the first generation, adult longevity was increased by approximately 2 d, and cocoon to adult and egg to adult developmental times were prolonged by approximately 1 d in parasitoids exposed to transgenic sugarcane, whereas effects were not evident on adult size; egg load; egg to cocoon developmental time; rates of gain of longevity and egg load with adult size; and egg, larval, and pupal mortality. However, in the second generation, adult longevity was reduced by approximately 3 d, adult size by approximately 5%, egg load by approximately 24%, and rate of gain of longevity with adult size by approximately 21%, whereas effects were not evident on the rate of gain of egg load with adult size. It was concluded that although GNA transgenic sugarcane, ingested via E. loftini tissues, was not acutely toxic to P. pyralophagus, the sublethal effects on life history parameters measured in this study must be considered in a broader context to determine their possible ecological significance.     

Combining electron microscopic with x-ray crystallographic structures

Analgorithm has been developed for placing three-dimensional atomic structures into appropriately scaled cryoelectron microscopy maps. The first stage in this process is to conduct a three-dimensional angular search in which the center of gravity of an X-ray crystallographically determined structure is placed on a selected position in the cryoelectron microscopy map. The quality of the fit is measured by the sum of the density at each atomic position. The second stage is to refine the three angles and three translational parameters for the best (usually 25 to 100) fits. Useful criteria for this refinement include the sum of densities at atomic sites, the lack of atoms in negative or low density, the absence of atomic clashes between symmetry-related positions of the atomic structure, and the distances between identifiable features in the map and their positions on the fitted atomic structure. These refinements generally lead to a convergence of the originally chosen, top scoring fits to just a few (about 3 to 8) acceptable possibilities. Usually, the best remaining fit is clearly superior to any of the others.     

Tolerance and bioaccumulation of copper in Phragmites australis and Zea mays

The effects of copper on the growth, tolerance indices, mineral composition (N, P, K, Fe, Zn and Mn) and metal uptake of reed (Phragmites australis [Cav. Trin. ex Steudel]) and maize (Zea mays L.) were investigated in hydroponic experiments at copper concentrations ranging from 0.5 to 157 M Cu. A reduction in root length was shown to be a good indicator of copper toxicity, concentrations of 15.7 and 78.7 M Cu inhibiting root growth in maize and reed, respectively. The reed was significantly more tolerant of copper than maize and at 7.85 M Cu (external concentration), reed can be described as a Cu tolerant plant, and maize as a Cu non-tolerant species. As a result of Cu toxicity, the concentrations of macronutrients N, P and K decreased in both shoot and root of maize, while the concentrations were hardly affected in reed tissues. Fe concentration increased in shoots and roots of maize and in roots of reed with increasing Cu treatments, leading to highly significant (p<0.01) linear relationships between tissue Fe and Cu concentrations. The bioconcentration factor (BCF) of Cu was higher in roots than in shoots of both plant species, ranging from 612 to 1592 in reed for the Cu treatments tested. In the roots of maize, BCF of Cu increased from 349 to 1931 when increasing Cu in nutrient solution from 7.85 M to 78.5 M. Therefore, reed could be useful in wastewater treatments for the removal of Cu. However, the use of reed in phytoextraction of Cu from contaminated soils is limited by the low accumulation rate in shoots and although reed can be more efficient than maize for Cu phytoextraction, harvesting the full biomass, including roots, may be required.     

Oral hydratation with a low osmolality solution in dehydrated children with diarrheic diseases: controlled clinical trial

A clinical trial was conducted to compare the efficacy of a low-osmolarity solution (245 mOsm/L), and a standard oral rehydration solution (ORS) recommended by WHO for children dehydrated by diarrhea. Group 1 (69 children) received WHO/ORS (311 mOsml/L) and group 2 (71 children) received a low-osmolarity solution (245 mOsm/L). Rehydration was successful in 88.4% in group 1 and 92.9% in group 2 (p = 0.35). Rehydration was completed in 5.2 h (SD +/- 1.8) in group 1 and 5.5 (SD +/- 1.7) in group 2 (p = 0.31). Stool output was 6.3 g/kg/h (SD +/- 5.0) in group 1 and 5.6 g/kg/h (SD +/- 5.1) in group 2 (p = 0.94). Sodium at rehydration-completion was 139.3 mEq/L (SD +/- 7.1) in group 1 and 136.7 mEq/L (SD +/- 4.3) in group 2 (p = 0.014). Group 1 was under observation for 21 hours (SD +/- 5.7) and group 2, for 22 hours (SD +/- 5.6). Stool output in group 1 was 5.2 g/kg/h (SD 4.1) and 4.2 gr./kg/h (SD +/- 4.1) in group 2 (p = 0.16). In group 1, 23.1% required intravenous solutions and 9.8% in group 2 (p = 0.03). In treating dehydrated children, the low-osmolarity solution diminished the need for intravenous solutions, corrected most plasmatic sodium disorders, and produced no-risk of developing hyponatremia.     

avrPto enhances growth and necrosis caused by Pseudomonas syringae pv.tomato in tomato lines lacking either Pto or Prf

AvrPto was introduced into three tomato genotypes with two biotic agents to study its role in compatible interactions. avrPto enhanced the capacity of the Pseudomonas syringae pv. tomato strain T1 to induce necrotic symptoms on tomato plants that lacked either Pto or Prf genes. The enhanced necrosis correlated with a small increase in bacterial growth. In planta expression of avrPto in isolation did not elicit necrosis in the absence of a functional Prf gene.     

Fetal surfactant as a source of arachidonate in human amniotic fluid

The factors responsible for the onset of labor in women are not well understood but it is clear that parturition is associated with increased production of prostanoids and release of arachidonic acid by intrauterine tissues. Pulmonary surfactant is secreted from the fetal lung into the amniotic fluid where its concentration increases toward term. In this paper we have shown that the ability of fetal surfactant to stimulate prostaglandin production by amnion cells is greatly enhanced by pre-incubating surfactant with amniotic fluid. This is due to the release of fatty acids, including arachidonate, from the lipids of fetal surfactant by the sequential action of phospholipase C and diglyceride lipase. Thus, in addition to providing the amnion with a source of arachidonate derived from the intracellular transfer of arachidonate from surfactant phosphatidylcholine to phosphatidylethanolamine and phosphatidylinositol in amnion cells, fetal surfactant also contributes to the pool of free arachidonate in amniotic fluid.     

The Pleckstrin Homology and Phosphotyrosine Binding Domains of Insulin Receptor Substrate 1 Mediate Inhibition of Apoptosis by Insulin

Insulin and insulin-like growth factor 1 (IGF-1) evoke diverse biological effects through receptor-mediated tyrosine phosphorylation of insulin receptor substrate (IRS) proteins. We investigated the elements of IRS-1 signaling that inhibit apoptosis of interleukin 3 (IL-3)-deprived 32D myeloid progenitor cells. 32D cells have few insulin receptors and no IRS proteins; therefore, insulin failed to inhibit apoptosis during IL-3 withdrawal. Insulin stimulated mitogen-activated protein kinase in 32D cells expressing insulin receptors (32D^IR) but failed to activate the phosphatidylinositol 3 (PI 3)-kinase cascade or to inhibit apoptosis. By contrast, insulin stimulated the PI 3-kinase cascade, inhibited apoptosis, and promoted replication of 32D^IR cells expressing IRS-1. As expected, insulin did not stimulate PI 3-kinase in 32D^IR cells, which expressed a truncated IRS-1 protein lacking the tail of tyrosine phosphorylation sites. However, this truncated IRS-1 protein, which retained the NH₂-terminal pleckstrin homology (PH) and phosphotyrosine binding (PTB) domains, mediated phosphorylation of PKB/akt, inhibition of apoptosis, and replication of 32D^IR cells during insulin stimulation. These results suggest that a phosphotyrosine-independent mechanism mediated by the PH and PTB domains promoted antiapoptotic and growth actions of insulin. Although PI 3-kinase was not activated, its phospholipid products were required, since LY294002 inhibited these responses. Without IRS-1, a chimeric insulin receptor containing a tail of tyrosine phosphorylation sites derived from IRS-1 activated the PI 3-kinase cascade but failed to inhibit apoptosis. Thus, phosphotyrosine-independent IRS-1-linked pathways may be critical for survival and growth of IL-3-deprived 32D cells during insulin stimulation.