Identification and characterization of the vegetally localized Hermes mRNA

One way developing embryos regulate the expression of their genes is by localizing mRNAs to specific subcellular regions. In the oocyte of the frog, Xenopus laevis, many RNAs are localized specifically to the animal or the vegetal halves of the oocyte. The localization of these RNAs contributes to the primary polarity of the oocyte, the asymmetry that is the basis for patterning and lineage specification in the embryo. I have screened a cDNA library for clones containing the Xlsirt repeat, an element known to target RNAs to the vegetal cortex of the oocyte. I have identified seventeen cDNA clones that contain this element. One of these cDNAs encodes the RNA binding protein Hermes. The Hermes mRNA is localized to the vegetal cortex of the oocyte. Additionally, Hermes protein is also vegetally localized in the oocyte and is found in subcellular structures known to contain localized mRNAs. This suggests that Hermes might interact with localized RNAs. While Hermes protein is present in oocytes, it disappears at germinal vesicle breakdown during maturation. We therefore believe that the time period during which Hermes functions is during oogenesis or maturation prior to the time of Hermes degradation. To determine Hermes function, an antisense depletion strategy was used that involved injecting morpholino oligos (HE-MO) into oocytes. Injection of these morpholinos causes the level of Hennes protein to drop prematurely during maturation. Embryos produced from these oocytes exhibit cleavage defects that are most prevalent in the vegetal blastomeres. The phenotype can be partially rescued by injection of a heterologous Hermes mRNA and is therefore specific to Hermes. The Hermes expression and depletion results are consistent with a model in which Hermes interacts with one or more vegetally localized mRNAs in the oocyte and during the early stages of maturation. The interaction is required for cleavage of the vegetal blastomeres. Therefore, it is likely that at least one mRNA that interacts with Hermes is a cell cycle regulator. ^

Genetic analysis of Pitx2 in left -right asymmetry and cardiovascular development

Pitx2, a paired-related homeobox gene that is mutated in human Rieger Syndrome, plays a key role in transferring the early asymmetric signals to individual organs. Pitx2 encodes three isoforms, Pitx2a, Pitx2b and Pitx2c. I found that Pitx2c was the Pitx2 isoform for regulating left-right asymmetry in heart, lung and the predominant isoform in guts. Previous studies suggested that the generation of left-right asymmetry within individual organs is an all or none, random event. Phenotypic analysis of various Pitx2 allelic combinations, that encode graded levels of Pitx2c, reveals an organ-intrinsic mechanism for regulating left-right asymmetric morphogenesis based on differential response to Pitx2c levels. The heart needs low Pitx2c levels, while the lungs and duodenum require higher doses of Pitx2c. In addition, the duodenal rotation is under strict control of Pitx2c activity. Left-right asymmetry development for aortic arch arteries involves complex vascular remodeling. Left-sided expression of Pitx2c in these developing vessels implied its potential function in this process. In order to determine if Pitx2c also can regulate the left-right asymmetry of the aortic arch arteries, a Pitx2c-specific loss of function mutation is generated. Although in wild type mice, the direction of the aortic arch is always oriented toward the left side, the directions of the aortic arches in the mutants were randomized, showing that Pitx2c also determined the left-right asymmetry of these vessels. I have further showed that the cardiac neural crest wasn't involved in this vascular remodeling process. In addition, all mutant embryos had Double Outlet Right Ventricle (DORV), a common congenital heart disease. This study provided insight into the mechanism of Pitx2c-mediated late stages of left-right asymmetry development and identified the roles of Pitx2c in regulation of aortic arch remodeling and heart development. ^

Effects of Seed Treatments and a Soil-applied Nematicide on Corn Yields and Nematode Population Densities

Plant-parasitic nematodes are microscopic worms that feed on plants. Almost every nematode that feeds on corn is capable of feeding on many other plants. These nematode parasites are thought to be native to most Iowa soils and to have fed upon native plants before corn was grown as a cultivated crop. Population densities (numbers) of most species of plant-parasitic nematodes that feed on corn have to increase to damaging levels (called damage thresholds) before yield loss occurs.

National Elm Trial

Although many Dutch elm disease-resistant elm cultivars are available in the nursery trade, much of the public is hesitant to purchase and plant any elm tree. In order to promote interest in planting these trees, scientific data on growth, form, and pest resistance for existing Dutch elm disease resistant elm cultivars are essential.

Evaluation of Soybean Varieties Resistant to Soybean Cyst Nematode

Use of resistant soybean varieties is a very effective strategy for managing soybean cyst nematode (SCN), and numerous SCN-resistant soybean varieties are available for Iowa soybean growers. Each year, public and private SCN-resistant soybean varieties are evaluated in SCN-infested fields in Iowa by Iowa State University personnel. The research described in this report was performed to assess the agronomic performance of SCNresistant soybean varieties and to determine the effects of the varieties on SCN numbers or population densities.

Effectiveness of Foliar Fungicides by Timing on Hybrid Corn

Fungicides were rarely used on hybrid corn prior to 2007, however, in the past few years, some farmers have included fungicides in their common crop production, particularly as the value of grain has increased. Fungicides are recommended for foliar disease management to protect yield potential. There also have been reports of increased yields in the absence of disease. A number of fungicides are registered for use on corn. The objectives of this project were to evaluate the yield response of hybrid corn to foliar fungicide application at various timings.

On-farm Cooperator Trials 2011: Effect of Extended-duration Row Covers on Muskmelon and Winter Squash on Bacterial Wilt and Yield

Susceptible cucurbit crops are difficult to grow in Iowa because of bacterial wilt, caused by Erwinia tracheiphila. Striped and spotted cucumber beetles transmit bacterial wilt. Other insect pests such as squash vine borer and squash bugs may also have an economic impact on yield, particularly in squash.

Effects of Seed Treatments and a Soil-applied Nematicide on Corn Yields and Nematode Population Densities

Plant-parasitic nematodes are microscopic worms that feed on plants. Almost every nematode that feeds on corn is capable of feeding on many other plants. These nematode parasites are thought to be native to most Iowa soils and to have fed upon native plants before corn was grown as a cultivated crop. Population densities (numbers) of most species of plant-parasitic nematodes that feed on corn have to increase to damaging levels (called damage thresholds) before yield loss occurs.

Evaluation of Fungicides and Herbicides for Management of White Mold of Soybean

Several new fungicide products are either available or will be available for management of white mold of soybean. This study was conducted at the Muscatine Island Research and Demonstration Farm, and one farmer’s field in northeast Iowa.

Squash Bug, Squash Vine Borer, and Striped Cucumber Beetle on Butternut Squash and Muskmelon

Alternative agricultural schemes are gaining attention as the demand for organic and sustainable products continues to grow. Pest insects pose a sizeable challenge to agricultural production because their activities reduce crop fitness and productivity. Effective management of pest-insects is, therefore, crucial for successful management, and increasingly entails a multi-dimensional approach.

Soybean Planting Dates in Northeast Iowa

Soybean planting date studies of various types have been conducted at this site since 1976. Earlier tests included later planting dates (May through mid-June), differing variety maturities, and comparisons with starter fertilizer and Ridomil fungicide soil treatments. Research reports on these studies can be found in previous annual progress reports with the last summary in the 2001 and 2009 reports.

Weather Inputs to a Warning System for Sooty Blotch and Flyspeck of Apple

Sooty blotch and flyspeck (SBFS) is a mid- to late-season disease of apple. SBFS fungi show up as dark smudges and clusters of black dots on the fruit surface. Since blemished fruit are downgraded, crop losses can exceed 90 percent of the fresh market value.

Effectiveness of Foliar Fungicides by Timing on Hybrid Corn

Fungicide use on hybrid corn has increased considerably in the past four growing seasons primarily due to reports of increased yields, even in the absence of disease and higher corn prices. A number of fungicides are registered for use on corn. The objectives of this project were to 1) assess the effect of timing of application of fungicides on standability, 2) evaluate the yield response of hybrid corn to foliar fungicide application, and 3) to discern differences, if any, between fungicide products.

Testing a Warning System for Anthracnose Fruit Rot on Day-neutral Strawberry

Anthracnose fruit rot (AFR) of strawberry is caused by three Colletotrichum spp. In the Midwest, however, only Colletotrichum acutatum is found. This fungus can attach itself to apparently healthy plants and spread throughout without causing symptoms on the foliage. When fruit begin to ripen and weather conditions are rainy and warm, AFR can suddenly cause great damage to the fruit. To protect against AFR where it has appeared in the past, growers need to spray every 7 to 10 days beginning at the start of bloom until harvest.

Effect of Date of Planting on Soybean Sudden Death Syndrome

The objectives of this project was to study the effect of planting date on the onset of soybean sudden death syndrome (SDS). It is believed, that avoiding planting soybeans into wet cold soil may delay or lower the severity of SDS. Planting date for soybeans is important and can have a large effect on yield potential.