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.     

Assessing the impact of interfering organic matter on soil metaproteomic workflow

Soil organic matter (SOM) is biologically, chemically, and physically complex. As a major store of nutrients within the soil, it plays an important role in nutrient provision to plants. An enhanced understanding of SOM utilisation processes could underpin better fertiliser management for plant growth, with reduced environmental losses. Metaproteomics can allow the characterisation of protein profiles and could help gain insights into SOM microbial decomposition mechanisms. Here, we applied three different extraction methods to two soil types to recover SOM with different characteristics. Specifically, water-extractable organic matter, mineral-associated organic matter and protein-bound organic matter were targeted with the aim to investigate the metaproteome enriched in those extractions. As a proof-of-concept, replicated extracts from one soil were further analysed for peptide identification using liquid chromatography followed by tandem mass spectrometry. We employed a framework for mining mass spectra for both peptide assignment and fragmentation pattern characterisation. Different extracts were found to exhibit contrasting total protein and humic substance content for the two soils investigated. Overall, water extracts displayed the lowest humic substance content (in both soils) and the highest number of peptide identifications (in the soil investigated) with the most frequent peptide hits associated with diverse substrate/ligand binding proteins of Proteobacteria and derived taxa. Our framework also highlighted a strong peptidic signal in unassigned and unmatched spectra, information that is currently not captured by the pipelines employed in this study. Taken together, this work points to specific areas for optimisation in chromatography and mass spectrometry to adequately characterise SOM-associated metaproteomes.     

Effect of levels of take‐all and phosphorus fertiliser on the dry matter and grain yield of wheat

In a field experiment with wheat (Triticum aestivum L.), the effect of the percentage severity of take‐all on the production of dried tops and grain and the kernel weight (mg/seed) was measured when different amounts of phosphorus (P) fertiliser were applied. The soil was severely P deficient. The amounts of P fertitiser varied from nil P (deficient) to 40 kg P/ha (adequate) applied annually. The levels of Gaeumannomyces graminis tritici (Ggt) were generated by four cropping sequences. The levels of percent severity of Ggt on plant roots ranged from low (<10% of wheat plant roots infected) to high (70% of roots infected by Ggt). Yield of dried tops, grain, and kernal weight, all increased as the level of P applied increased, but the amount of Ggt infection decreased. No grain was produced where no P was applied. The percentage increase in yield due to declines in the severity of take‐all was greater as the level of P applied increased. Increasing levels of P fertiliser help control the severity of Ggt (%) only where the initial level of Ggt with nil P fertiliser are moderate to low. Where the levels of Ggt severity are >65% the effectiveness of P in reducing the levels of Ggt severity rapidly declined. The percentage severity of Ggt affected the efficiency of plants to use P fertilisers. For each cropping sequence, a Mitscherlich function described the grain yield response to P fertiliser. The maximum grain yield (A coefficient) and the curvature coefficient (C) both declined with increases in the level of Ggt severity (%). For example, the C was significantly reduced from 0.134±0.03 for the least Ggt severity (%) to 0.00446±0.001 where Ggt was not controlled. The kernal weight (mg/seed) was increased by P application and decreased by Ggt infection.     

The lipid compositions of two isolates of Cladosporium cucumerinum do not explain their differences in sensitivity to fungicides which inhibit sterol biosynthesis

Isolate 840905 of Cladosporium cucumerinum, when grown on agar or in liqiud medium, was sensitive to triadimenol, HWG 1608 (tebuconazole), fenpropimorph and pimaricin but relatively resistant to terbinafine. Conversely, isolate 49628 was sensitive to terbinafine but relatively resistant to the other fungicides. Changes in sterol composition following treatment with the fungicides reflected the known modes of action of each fungicide. When individual enantiomers of triadimenol were tested against isolate 840905 the order of activity in reducing mycelial growth was 1 S, 2R > 1R, 2R > 1R, 2S ≈? 1S, 2S, and this was paralleled by the depletion of ergosterol and the appearance of 14α-methyl sterols. Isolate 49628 had a greater saturated:unsaturated fatty acid ratio than did isolate 840905 but no major changes in fatty acid composition of either isolate were induced by fungicide treatment. There appears to be no obvious explanation for the differences in fungicide sensitivity of the isolates in terms of their lipid compositions.     

A note on changes in egg‐shell porosity with flock age and season during the first breeding cycle of domestic ducks

1. — Changes in egg weight and egg‐shell porosity with flock age and season are presented for domestic duck flocks in their first laying cycle.

2. — The first eggs laid are of low weight and shell porosity but generally by the fifth week of lay both characteristics have increased to the values found in the mature flock.

3. —For mature flocks porosity decreases in the summer and the consequences of this are considered in relation to the observed decrease in hatch‐ability at this time.     

Cross-sectional study on acrylamide hemoglobin adducts in subpopulations from the European Prospective Investigation into Cancer and Nutrition (EPIC) Study

Acrylamide exposure was investigated in subgroups of the EPIC study population (510 subjects from 9 European countries, randomly selected and stratified by age, gender, and smoking status) using hemoglobin adducts of acrylamide (HbAA) and its primary metabolite glycidamide (HbGA). Blood samples were analyzed for HbAA and HbGA by HPLC/MS/MS. Statistical models for HbAA and HbGA were developed including body mass index (BMI), educational level, and physical activity. A large variability in acrylamide exposure and metabolism between individuals and country groups was observed with HbAA and HbGA values ranging between 15-623 and 8-377 pmol/g of Hb, respectively. Both adducts differed significantly by country, sex, and smoking status. HbGA values were significantly lower in high alcohol consumers than in moderate consumers. With increasing BMI, HbGA in nonsmokers and HbAA in smokers decreased significantly. In the assessment of potential health effects related to acrylamide exposure, country of origin, BMI, alcohol consumption, sex, and smoking status should be considered.     

Genotypic variation in fatty acid content of blackcurrant seeds.

The fatty acid composition and total fatty acid content of seeds from 36 blackcurrant genotypes developed at the Scottish Crop Research Institute were examined. A rapid small-scale procedure, involving homogenization of seeds in toluene followed by sodium methoxide transesterification and gas chromatography, was used. There was considerable variation between genotypes. The gamma-linolenic acid content generally varied from 11 to 19% of the total fatty acids, but three genotypes had higher values of 22-24%, levels previously not reported for blackcurrant seed and similar to those for borage seed. Other nutritionally important fatty acids, stearidonic acid and alpha-linolenic acid, varied from 2 to 4% and 10-19%, respectively. The mean total fatty acid contents ranged from 14 to 23% of the seed, but repeatability was poor. The results are discussed. Blackcurrant seeds are mainly byproducts from juice production, and the study shows the potential for developing blackcurrant genotypes with optimal added value.     

Long-Term Residual Value of Zinc Fertilizer for Pasture Legumes Using Yield of Dried Herbage and Critical Concentration of Zinc in Young Tissue

The zinc (Zn) requirements of subterranean clover (Trifolium subteraneaum L.) are well known for the predominantly marginally acidic to neutral sandy soils of southwestern Australia, but the Zn requirements of French serradella (Ornithopus sativus Brot.) and biserrula (Biserrula pelecinus L.), now also grown on these soils, is not known and were investigated in a glasshouse pot experiment. Soil was collected from field plots never treated with Zn or treated once only with 0.5 and 1.0 kg Zn/ha as Zn oxide either in 1983, 1984, 1986, 1990, 1992, 1996, 1997, or 2000. In the pot experiment, six levels of Zn were freshly-applied to samples of soil collected from each Zn treatment of the field experiment, and pots were sown either with subterranean clover cv. ‘Dalkeith’, French serradella cv. ‘Margurita’, or biserrula cv. ‘Casbah’. The pasture species were defoliated by cutting pasture herbage 3 cm above the soil surface for up to 4 consecutive defoliations. The approximate linear relationship between the level of freshly-applied Zn in the pot experiment required to produce 90% of the maximum yield of dried defoliated herbage (y-axis) and the number of years since Zn was applied in the field (x-axis) was used to project the number of years it took for the 0.5 or 1.0 kg Zn/ha treatments applied in the field to require the same level of freshly-applied Zn to produce 90% of the maximum yield of the nil-Zn treatment in the field. This was 18–19 years for the 0.5 kg Zn/ha treatment and 32–35 years for the 1.0 kg Zn/ha treatment. The range in values was due to differences between legume species and the defoliation treatments, which were not significant. When yields were measured, samples of young growth (YG) were separated from the rest of the defoliated herbage (ROH) and the concentration of Zn in YG and ROH was measured. The concentration of Zn in YG that was related to 90% of the maximum yield of defoliated dried herbage (critical tissue test value) was (mg/kg) 13 for subterranean clover, 17 for French serradella, and 19 for biserrula; respective critical tissue test values for ROH were 19, 24, and 21 mg/kg. The approximate linear relationship between critical Zn concentration in YG (y-axis) and the number of years since Zn was applied in the field (x-axis) was used to project the number of years it took for the 0.5 and 1.0 kg Zn/ha levels applied in the field to reach the same critical tissue test value as the nil-Zn treatment of the field experiment. This was 17–20 years for the 0.5 kg Zn/ha treatment and 31–37 years for the 1.0 kg/ha treatment, which was similar to the 18–19 and 32–35 years projected using yield data. Before sowing the legumes in the pot study soil samples were collected to measure soil test Zn using the DTPA procedure. The critical DTPA soil test Zn, the soil test value that was related to 90% of the maximum yield of defoliated dried herbage, was about 0.20 mg Zn/kg for the 3 pasture legume species and all Zn treatments in the field and pot studies.     

Significant Nitrogen by Sulfur Interactions Occurred for Canola Grain Production and Oil Concentration in Grain on Sandy Soils in the Mediterranean-Type Climate of Southwestern Australia

The nitrogen (N) by sulfur (S) interaction for canola (Brassica napus L.) grain production and oil concentration in grain has been quantified in temperate climates, but it is not known if these results also apply to sandy soils common in the Mediterranean-type climate of southwestern Australia where canola is now a major crop. Seventeen field experiments were undertaken with canola in the region during 1994 to 2005 in which 4 rates of both N (0–138 kg N/ha) and S (0–34 kg S/ha) were applied. Significant grain yield responses to applied N occurred in all experiments and the responses increased as more S was applied. Grain yield responses to applied S only occurred when N was applied and tended to increase as more N was applied. When no S was applied the two largest rates of N applied, 69 and 138 kg N/ha, induced S deficiency reducing grain yields. The oil concentration in grain tended to decrease as more N was applied and increased as more S was applied, particularly when the two largest rates of N were applied. Consequently significant N × S interactions were obtained in all experiments for grain production and in 15 experiments for oil concentration in grain.