Molecular biology of male gametogenesis

Pollen development has been studied at a molecular level in several systems that are amenable to genetic or transgenic analysis. We have characterized several tomato genes that are expressed late in pollen development. Our goals in this research were 1) to determine the cis- and tran-acting factors that mediate pollen expression, and 2) to determine the functions of the proteins encoded by these genes. We currently favor the hypothesis that pollen-specific gene expression is mediated in a combinatorial manner. Antisense experiments have indicated an important role for the LAT52 protein during pollen hydration.     

A selective, sensitive, and rapid in-field assay for soil catechin, an allelochemical of Centaurea maculosa

Centaurea maculosa is a plant species native to Eurasia and invasive in many regions of North America that secretes a phytotoxin from its roots, (+/−)-catechin, which is thought to serve an allelopathic role by reducing fitness of neighboring species. However, catechin is a relatively unstable compound, is often found at relatively low concentrations, interacts with soil cations to form insoluble complexes and/or degradation products, and exhibits extremely variable accumulation patterns in the soil. These factors, coupled with a lack of knowledge of the regulation of catechin production by C. maculosa, confound our understanding of the importance of catechin as an allelochemical. The time and cost of current sampling procedures effectively limit the observations made on catechin accumulation patterns, without which it is extremely difficult to conclusively attribute allelopathic significance to this compound. Thus, a highly sensitive, fast, inexpensive and reliable method for soil catechin analysis is needed. We report a novel method that utilizes the colorimetric reagent dimethylaminocinnamaldehyde (DMACA) in an acidic ethanol solution for detection of soil catechin. This method is selective and extremely sensitive and can be used in the field for qualitative, but not quantitative, analysis. This assay will allow for a greater understanding of the role of catechin as an allelochemical.     

Classification of Peruvian highland maize races using plant traits

The maize of Latin America, with its enormous diversity, has played an important role in the development of modern maize cultivars of the American continent. Peruvian highland maize shows a high degree of variation stemming from its history of cultivation by Andean farmers. Multivariate statistical methods for classifying accessions have become powerful tools for classifying genetic resources conservation and the formation of core subsets. This study has two objectives: (1) to use a numerical classification strategy for classifying eight Peruvian highland races of maize based on six vegetative traits evaluated in two years and (2) to compare this classification with the existing racial classification. The numerical classification maintained the main structure of the eight races, but reclassified parts of the races into new groups (Gi). The new groups are more separated and well defined with a decreasing accession within group × environment interaction. Most of the accessions from G1 are from Cusco Gigante, all of the accessions from G3 (except one) are from Confite Morocho, and all of the accessions from G7 are from Chullpi. Group G2 has four accessions from Huayleño and four accessions from Paro, whereas G4 has four accessions from Huayleño and five accessions from San Geronimo. Group G5 has accessions from four races, and G6 and G8 formed small groups with two and one accession each, respectively. These groups can be used for forming core subsets for the purpose of germplasm enhancement and assembling gene pools for further breeding.     

Soil erosion modelling of burned and mulched soils following a Mediterranean forest wildfire

Soil erosion modelling applied to burned forests in different global regions can be unreliable because of a lack of verification data. Here, we evaluated the following three erosion models: (1) Water Erosion Prediction Project (WEPP), (2) Morgan-Morgan-Finney (MMF) and (3) Universal Soil Loss Equation-Modified (USLE-M). Using field plots that were either untreated or mulched with straw, this study involved observations of soil loss at the event scale at a burned pine forest in Central Eastern Spain. The erosion predictions of the three models were analysed for goodness-of-fit. Optimization of the MMF model with a new procedure to estimate the C-factor resulted in a satisfactory erosion prediction capacity in burned plots with or without the mulching treatment. The WEPP model underestimated erosion in the unburned areas and largely overestimated the soil loss in burned areas. The accuracy of soil loss estimation by the USLE-M model was also poor. Calibration of the curve numbers and C-factors did not improve the USLE-M model estimation. Therefore, we conclude that an optimized MMF model was the most accurate way to estimate soil loss and recommend this approach for in Mediterranean burned forests with or without postfire mulching. This study gives land managers insight about the choice of the most suitable model for erosion predictions in burned forests.     

Antioxidant capacity and phenolic content of grapes, sun-dried raisins, and golden raisins and their effect on ex vivo serum antioxidant capacity

Grapes and raisins provide phenolic antioxidants, which contribute to their potential health benefits. The objectives of this study were to compare the antioxidant capacity and phenolic content of green Thompson seedless grapes (the most common variety of grapes consumed in the United States), sun-dried raisins, and golden raisins (both produced from Thompson seedless grapes) and to observe the effects of their consumption over 4 weeks in 15 healthy human males with a cross-over design. The oxygen radical absorbance capacity (ORAC) (positive statistical significance for grapes after 2 weeks and golden raisins after 3 weeks), serum oxidation (positive statistical significance for golden raisin lag time after 4 weeks), total phenolics (no significant effects), and C-reactive protein (no significant effects) were monitored. Immediately postconsumption, there were some significant nonpositive changes. It is hypothesized that these negative results may be explained by postprandial oxidation, a known effect after carbohydrate consumption. Golden raisins had the highest antioxidant capacity and phenolic content. The consumption of a serving of grapes or raisins each day, in addition to a typical diet, may not be sufficient to overcome postprandial oxidation when consumed with other high carbohydrate foods but may have beneficial antioxidant effects over time.     

Primary and secondary metabolite composition of kernels from three cultivars of Portuguese chestnut (Castanea sativa Mill.) at different stages of industrial transformation

Chestnut (Castanea sativa) is an important basic food in rural diets and a major starch crop used in a similar way to potatoes. Chestnuts are a fundamental economic resource in the "chestnut regions" not only for the fruit but also for the chestnut wood. Chestnuts have become increasingly important with respect to human health, for example, as an alternative gluten-free flour source. Chestnuts are also a rich source of other beneficial compounds, but there have been few studies on the composition during processing. In this study, we analyzed the chemical composition of three Portuguese cultivars at different stages of industrial processing. The chestnut cultivars were Longal, Judia, and Martaínha. All three cultivars had high moisture contents but were low in ash, crude fat, and crude protein contents, with high starch and low fiber contents. The free amino acid contents, including various essential amino acids, varied depending on the cultivar. All three cultivars also had a significant content of polyphenolics with gallic acid; ellagic acid was predominant among hydrolyzable and condensed tannins. Many of these compounds are known to exert significant positive effects on human health. The one-way analysis of variance for fresh chestnut shows significant differences among the three cultivars for most of the studied parameters. The same statistical analysis applied to each one of the two cultivars (Judia and Longal) sampled for the four processing steps analyzed indicates a significant effect of this factor in practically all of the constituents. On the other hand, the two-way analysis of variance shows that, besides the residual, the processing step and the interaction cultivar x processing step were the factors that more contributed for the total variation observed in the constituents analyzed, while the contribution of cultivar was much less significant.     

Modeling the Interfacial Interactions between CrtS and CrtR from Xanthophyllomyces dendrorhous , a P450 System Involved in Astaxanthin Production

Xanthophyllomyces dendrorhous is a natural source of astaxanthin, a carotenoid widely used in the food industry. In this yeast, astaxanthin is synthesized from β-carotene by a cytochrome P450, CrtS, which depends on CrtR, the four-domain cytochrome P450 reductase (CPR). Although Saccharomyces cerevisiae has an endogenous CPR (ScCPR), expression of CrtS does not result in astaxanthin production unless it is coexpressed with CrtR. Assuming that CrtS could interact with the FMN-binding domain of either CrtR or ScCPR (XdFMNbd and ScFMNbd, respectively), the aim of this work was to identify possible interaction differences between these alternative complexes by protein modeling and short molecular dynamics simulations. Considering the recently proposed membrane orientation of a mammalian P450, our CrtS-CrtR model predicts that both N-terminal ends stand adjacent to the membrane plane, allowing their anchoring. Compared with the possible interface between CrtS and both FMNbd, the Xanthophyllomyces system appears to be stabilized by more saline bridges.     

Assessment of Boron Application in Chestnuts: Nut Yield and Quality

A field trial was conducted between 2006 and 2009 in order to quantify the effect of boron (B) application on the yield and quality of chestnuts. The trial was established in an acid soil derived from siliceous schist and two levels of B were applied. Fruit abortion and nut yield per tree were measured, and nut quality parameters and chemical composition of the kernel were determined. Foliar B concentration was 8.6 mg kg^?1 in the control trees and 48.4 mg kg^?1 in fertilized chestnuts. Boron improved fruit setting and promoted nut production by 77%. In 2008, the occurrence of cold temperatures enhanced the effect of B on fruit setting, which was four-fold, whereas with the normal temperatures of 2009 the increase was lower. The drought of 2009 was responsible for the ruinous chestnut caliber and shell cracking. Boron induced a significant increase in the crude fat of chestnut kernel.     

Isozyme diversity and analysis of the mating system of the wild rice Oryza latifolia Desv. in Costa Rica

Oryza latifolia is the most abundant and widespread wild relative of rice in the lowlands of Costa Rica. It also has the most diverse morphology. However, little is known about the genetic diversity and mating system of this allotetraploid species. Genetic analyses of nine populations from different life zones from the Pacific and Atlantic slopes were performed using six isozyme loci. Differences in genetic variability were observed among populations, of which Palo Verde and Santa Rosa were the most diverse. Most Atlantic populations clustered together, and a similar result was obtained with the Pacific populations. High levels of interpopulation diversity were observed while most populations were monomorphic for at least one genotype, suggesting little genetic flow within populations. Even in polymorphic populations no variation was observed within progeny groups, combined with Hardy-Weinberg disequilibria in most populations, commonly observed in autogamous species or in species with clonal reproduction. However, the high frequency of heterozygous-like patterns may suggest that the reproductive system of O. latifolia might be more complex. Future research may explain the genetic patterns as well as the reproductive biology of this species. The knowledge of the genetic diversity and mating system of O. latifolia could contribute to the implementation of genetic resource conservation strategies and gene flow analyses, as well as of breeding programs for rice improvement.     

Mercury in Biota and Surficial Sediments from Coatzacoalcos Estuary, Gulf of Mexico: Distribution and Seasonal Variation

Variation of mercury (Hg) in sediments and biota from Coatzacoalcos estuary during the dry, rainy and windy seasons was estimated. In sediments, Hg concentrations ranged from 0.07 μg g^?1 in site 13 (Ixhuatepec) located upstream, to 1.06 μg g^?1 in site 3 (Coatzacoalcos river), located in the industrialized area. Highest enrichment factor (EF) and index of geoaccumulation (I _geo) in surficial sediments were 53 and 5.1 respectively. From EF and I _geo, it is considered that Coatzacoalcos estuary is from moderately contaminated to contaminated. In most fish species from Coatzacoalcos estuary, the sequence of Hg concentration was liver>muscle>gills. Average Hg concentrations in soft tissue of bivalves ranged from 0.09 μg g^?1 in Corbicula fluminea to 0.18 μg g^?1 in Polymesoda caroliniana. Biota-sediment accumulation factor (BSAF) ranged from 0.9 in P. caroliniana during the rainy season (site 4) to 3.8 in P. caroliniana from the same site during the windy season.