Relationship of Heliothis zea predators, parasitoids and entomopathogens to canopy development in soybean as affected by Heterodera glycines and weeds

The influence of canopy development in soybean on the survival of corn earworm, Heliothis zea (Boddie) (Lepidoptera: Noctuidae), egg and larval stages and population dynamics of arthropod fauna were evaluated in field trials during 1986–88 in eastern North Carolina. Soybean canopy size decreased as soybean cyst nematode, Heterodera glycines Ichinohe (Nematoda: Heteroderidae), initial population densities increased. Plant species composition of the soybean canopy was affected by weed population densities. Mortality of H. zea larvae due to parasitism and infection with entomopathogens was greater in closed canopy and (or) weedy soybeans than in very open and (or) weed free soybeans. Predation and parasitism of corn earworm eggs were similar across nematode and weed density treatments. Natural enemy populations increased to highest levels during July in closed canopy and (or) weedy soybeans, coinciding with availability of largest prey population reservoirs. A delay in colonization of very open and (or) weed free soybeans by beneficial arthropods until mid to late August allowed greater H. zea larval survival than in closed canopy and (or) weedy soybeans. Arthropod species richness was generally greatest in closed canopy and (or) weedy soybeans during mid to late July, with differences becoming nonsignificant in August and early September. Mean and maximum ambient temperatures were higher and relative humidities lower in open canopy than in closed canopy plots. These conditions were less favorable for development of pathogens and natural enemies.     

Myeloperoxidase reduces the opsonizing activity of immunoglobulin G and complement component C3b

The effect of myeloperoxidase, hydrogen peroxide (H2O2) and a halide (Cl) on the opsonizing molecules in immunoglobulin G (IgG) and complement factor C3b was assayed. At concentrations of the enzyme (1 microgram/ml) that can be found in the extracellular fluid during inflammation, the myeloperoxidase-H2O2-Cl system inhibited the opsonizing effect of IgG and C3b measured as phagocytic uptake and superoxide generation. The effect was related to the enzymatic peroxidative activity of the protein. The presence of albumin (10 mg/ml) reduced the effect of myeloperoxidase with 10-20%. Taurine, which in the presence of myeloperoxidase-H2O2-Cl forms hydrophilic chloramines, and D-penicillamine, which scavenges HOCl, neutralize the inhibitory effect of myeloperoxidase. This suggests that either hypochlorous acid or lipophilic chloramines may exert its effect by oxidizing free sulphydryl groups exposed on the opsonizing ligands. Since the myeloperoxidase-H2O2-halide system also affects chemotactic factors, leukotrienes, proteinases and membrane receptors, the system may in several ways affect the development of the inflammatory response.     

Effect of Cyclanilide on Auxin Activity

Cyclanilide is a plant growth regulator that is registered for use in cotton at different stages of growth, to either suppress vegetative growth (in combination with mepiquat chloride) or accelerate senescence (enhance defoliation and boll opening, used in combination with ethephon). This research was conducted to study the mechanism of action of cyclanilide: its potential interaction with auxin (IAA) transport and signaling in plants. The activity of cyclanilide was compared with the activity of the auxin transport inhibitors NPA and TIBA. Movement of [³H]IAA was inhibited in etiolated corn coleoptiles by 10 μM cyclanilide, NPA, and TIBA, which demonstrated that cyclanilide affected polar auxin transport. Although NPA inhibited [³H]IAA efflux from cells in etiolated zucchini hypocotyls, cyclanilide had no effect. NPA did not inhibit the influx of IAA into cells in etiolated zucchini hypocotyls, whereas cyclanilide inhibited uptake 25 and 31% at 10 and 100 μM, respectively. Also, NPA inhibited the gravitropic response in tomato roots (85% at 1 μM) more than cyclanilide (30% at 1 μM). Although NPA inhibited tomato root growth (30% at 1 μM), cyclanilide stimulated root growth (165% of control at 5 μM). To further characterize cyclanilide action, plasma membrane fractions from etiolated zucchini hypocotyls were obtained and the binding of NPA, IAA, and cyclanilide studied. Cyclanilide inhibited the binding of [³H]NPA and [³H]IAA with an IC₅₀ of 50 μM for both. NPA did not affect the binding of IAA, nor did IAA affect the binding of NPA. Kinetic analysis indicated that cyclanilide is a noncompetitive inhibitor of both NPA and IAA binding, with inhibition constants (K _i) of 40 and 2.3 μM, respectively. These data demonstrated that cyclanilide interacts with auxin-regulated processes via a mechanism that is distinct from other auxin transport inhibitors. This research identifies a possible mechanism of action for cyclanilide when used as a plant growth regulator.     

Watershed ‘chemical cocktails’: forming novel elemental combinations in Anthropocene fresh waters

In the Anthropocene, watershed chemical transport is increasingly dominated by novel combinations of elements, which are hydrologically linked together as ‘chemical cocktails.’ Chemical cocktails are novel because human activities greatly enhance elemental concentrations and their probability for biogeochemical interactions and shared transport along hydrologic flowpaths. A new chemical cocktail approach advances our ability to: trace contaminant mixtures in watersheds, develop chemical proxies with high-resolution sensor data, and manage multiple water quality problems. We explore the following questions: (1) Can we classify elemental transport in watersheds as chemical cocktails using a new approach? (2) What is the role of climate and land use in enhancing the formation and transport of chemical cocktails in watersheds? To address these questions, we first analyze trends in concentrations of carbon, nutrients, metals, and salts in fresh waters over 100 years. Next, we explore how climate and land use enhance the probability of formation of chemical cocktails of carbon, nutrients, metals, and salts. Ultimately, we classify transport of chemical cocktails based on solubility, mobility, reactivity, and dominant phases: (1) sieved chemical cocktails (e.g., particulate forms of nutrients, metals and organic matter); (2) filtered chemical cocktails (e.g., dissolved organic matter and associated metal complexes); (3) chromatographic chemical cocktails (e.g., ions eluted from soil exchange sites); and (4) reactive chemical cocktails (e.g., limiting nutrients and redox sensitive elements). Typically, contaminants are regulated and managed one element at a time, even though combinations of elements interact to influence many water quality problems such as toxicity to life, eutrophication, infrastructure corrosion, and water treatment. A chemical cocktail approach significantly expands evaluations of water quality signatures and impacts beyond single elements to mixtures. High-frequency sensor data (pH, specific conductance, turbidity, etc.) can serve as proxies for chemical cocktails and improve real-time analyses of water quality violations, identify regulatory needs, and track water quality recovery following storms and extreme climate events. Ultimately, a watershed chemical cocktail approach is necessary for effectively co-managing groups of contaminants and provides a more holistic approach for studying, monitoring, and managing water quality in the Anthropocene.     

IDENTIFICATION AND DNA SEQUENCE OF A NEW H+-ATPase IN THE UNICELLULAR GREEN ALGA CHLAMYDOMONAS REINHARDTII (CHLOROPHYCEAE)

Insertional mutagenesis was used to identify genes involved in mating and/or zygote formation in the unicellular green alga Chlamydomonas reinhardtii Dangeard. Approximately 800 insertionally mutagenized transformants were examined, and a single nonagglutinating mutant was identified. Plasmid rescue was used to clone a genomic fragment containing transforming DNA. This fragment was then used to identify the wild-type copy of the gene disrupted during mutagenesis. The wild-type gene is transcribed during all stages of the life cycle and, based on sequence similarity, encodes a P2-type proton transporting ATPase. The gene is referred to as Pmh1 for plasma membrane H ⁺ -ATPase. PMH1 displays the greatest sequence similarity to ATPases from two parasitic flagellates and a raphidophytic alga but not to the ATPase from a closely related green alga. We propose that PMH1 represents a distinct H ⁺ -ATPase isoform expressed in flagellates.     

Genetic basis of resistance to Cry1Ac and Cry2Aa in Heliothis virescens (Lepidoptera: Noctuidae)

The development of pest resistance to transgenic crop plants producing insecticidal toxins from Bacillus thuringiensis Berliner (Bt) poses a major threat to their sustainable use in agriculture. "Pyramiding" two toxins with different modes of actions in the same plant is now being used to delay the evolution of resistance in the insects, but this strategy could fail if a single gene in a pest confers resistance to both toxins. The CP73 strain of the cotton pest Heliothis virescens (F.) is resistant to both Cry1Ac and Cry2Aa toxins from Bt. We explored the genetic basis of resistance in this strain with a backcross, split-family design. The gene with the largest effect on Cry1Ac resistance in CP73 (BtR-5) maps to linkage group 10 of H. virescens and thus differs from the previously described linkage group 9 BtR-4 resistance found in the YHD2 strain, involving mutation of the gene encoding a 12-domain cadherin-like binding target of the Cry1A toxins. Neither BtR-4 nor BtR-5 seems to confer significant resistance to Cry2Aa. A majority of the linkage groups studied in one backcross family made a small positive contribution to resistance for both toxins. Thus, the Cry2Aa resistance in CP73 is not caused by either of the two major Cry1Ac resistance-conferring genes but instead probably has a quantitative genetic basis.     

Demographic History of Indigenous Populations in Mesoamerica Based on mtDNA Sequence Data

The genetic characterization of Native American groups provides insights into their history and demographic events. We sequenced the mitochondrial D-loop region (control region) of 520 samples from eight Mexican indigenous groups. In addition to an analysis of the genetic diversity, structure and genetic relationship between 28 Native American populations, we applied Bayesian skyline methodology for a deeper insight into the history of Mesoamerica. AMOVA tests applying cultural, linguistic and geographic criteria were performed. MDS plots showed a central cluster of Oaxaca and Maya populations, whereas those from the North and West were located on the periphery. Demographic reconstruction indicates higher values of the effective number of breeding females (Nef) in Central Mesoamerica during the Preclassic period, whereas this pattern moves toward the Classic period for groups in the North and West. Conversely, Nef minimum values are distributed either in the Lithic period (i.e. founder effects) or in recent periods (i.e. population declines). The Mesomerican regions showed differences in population fluctuation as indicated by the maximum Inter-Generational Rate (IGRmax): i) Center-South from the lithic period until the Preclassic; ii) West from the beginning of the Preclassic period until early Classic; iii) North characterized by a wide range of temporal variation from the Lithic to the Preclassic. Our findings are consistent with the genetic variations observed between central, South and Southeast Mesoamerica and the North-West region that are related to differences in genetic drift, structure, and temporal survival strategies (agriculture versus hunter-gathering, respectively). Interestingly, although the European contact had a major negative demographic impact, we detect a previous decline in Mesoamerica that had begun a few hundred years before.     

Uptake of ammonium and soluble reactive phosphorus in forested streams: influence of dissolved organic matter composition

Many microbes responsible for inorganic nutrient uptake and transformation utilize dissolved organic matter (DOM) as a nutrient or energy source, but little is known about whether DOM composition is an important driver of nutrient uptake in streams. Our goal was to determine whether incorporating DOM composition metrics with other more commonly considered biological, physical, and chemical variables improved our ability to explain patterns of ammonium (\({\text{NH}}_{4}^{ + }\)–N) and soluble reactive phosphorus (SRP) uptake across 11 Lake Superior tributaries. Nutrient uptake velocities (V_f) ranged from undetectable to 14.6 mm min^?1 for \({\text{NH}}_{4}^{ + }\)–N and undetectable to 7.2 mm min^?1 for SRP. Logistic regressions suggested that DOM composition was a useful predictor of where SRP uptake occurred (4/11 sites) and \({\text{NH}}_{4}^{ + }\)–N concentration was a useful predictor of where \({\text{NH}}_{4}^{ + }\)–N uptake occurred (9/11 sites). Multiple regression analysis revealed that the best models included temperature, specific discharge, and canopy cover, and DOM composition as significant predictors of \({\text{NH}}_{4}^{ + }\)–N V_f. Partial least squares revealed fluorescence index (describing the source of aquatic fulvic acids), specific ultraviolet absorbance at 254 nm (an indicator of DOM aromaticity), temperature, and conductivity were highly influential predictors of \({\text{NH}}_{4}^{ + }\)–N V_f. Therefore, streams with higher temperatures, lower solute concentrations, more terrestrial DOM signal and greater aromaticity had greater \({\text{NH}}_{4}^{ + }\)–N V_f. Our results suggest that DOM composition may be an important, yet often overlooked, predictor of \({\text{NH}}_{4}^{ + }\)–N and SRP uptake in deciduous forest streams that should be considered along with commonly measured predictors.