A connection between pre-mRNA splicing and the cell cycle in fission yeast: cdc28+ is allelic with prp8+ and encodes an RNA-dependent ATPase/helicase.

The fission-yeast gene cdc28+ was originally identified in a screen for temperature-sensitive mutants that exhibit a cell-division cycle arrest and was found to be required for mitosis. We undertook a study of this gene to understand more fully the general requirements for entry into mitosis. Cells carrying the conditional lethal cdc28-P8 mutation divide once and arrest in G2 after being shifted to the restrictive temperature. We cloned the cdc28+ gene by complementation of the temperature-sensitive growth arrest in cdc28-P8. DNA sequence analysis indicated that cdc28+ encodes a member of the DEAH-box family of putative RNA-dependent ATPases or helicases. The Cdc28 protein is most similar to the Prp2, Prp16, and Prp22 proteins from budding yeast, which are required for the splicing of mRNA precursors. Consistent with this similarity, the cdc28-P8 mutant accumulates unspliced precursors at the restrictive temperature. Independently, we isolated a temperature-sensitive pre-mRNA splicing mutant prp8-1 that exhibits a cell-cycle phenotype identical to that of cdc28-P8. We have shown that cdc28 and prp8 are allelic. These results suggest a connection between pre-mRNA splicing and progression through the cell cycle.     

Unveiling of Novel Radiations within Trichodesmium Cluster by hetR Gene Sequence Analysis

The filamentous nonheterocystous cyanobacterial genus Katagnymene is a common diazotrophic component of tropical and subtropical oceans. To assess the phylogenetic affiliation of this taxon, two partial 16S rRNA gene sequences and 25 partial hetR gene sequences originating from the genera Katagnymene and Trichodesmium collected from open, surface waters of the Atlantic, Indian, and Pacific oceans were compared. Single trichomes or colonies were identified morphologically by using light microscopy and then used directly as templates in hetR PCR analyses. In addition, three cultured strains, identified as Katagnymene pelagica, Katagnymene spiralis, and Trichodesmium sp., were examined. The data show that the genus Katagnymene is in the Trichodesmium cluster and that K. pelagica Lemmermann and K. spiralis Lemmermann are most likely one species, despite their different morphologies. Phylogenetic analyses also unveiled four distinct clusters in the Trichodesmium cluster, including one novel cluster. Our findings emphasize the conclusion that known morphological traits used to differentiate marine nonheterocystous cyanobacteria at the genus and species levels correlate poorly with genetic data, and a revision is therefore suggested.     

Quantification of consumption of corn pollen by the predator Coleomegilla maculata (Coleoptera: Coccinellidae) during anthesis in an Illinois cornfield

Abstract 1 Coleomegilla maculata DeGeer feeds on corn pollen in the field, but the degree to which this predator relies on corn pollen as part of its diet is not well understood. We quantified the amount of pollen consumed by C. maculata second, third and fourth instars and adults in the field. 2 Laboratory experiments were conducted to determine the digestion rate and duration of different stadia or stages using temperature regimens that reflected field conditions during anthesis. Coleomegilla maculata larvae and adults were collected from the field and the amount of pollen in their digestive tracts was determined gravimetrically. The rate of digestion, duration of each life stage and the field observations were used to estimate the amount of pollen consumed by second, third and fourth instars and adults. 3 Our models estimate that larvae consume 0.66, 1.67 and 3.30 mg of pollen during the second, third and fourth stadia, respectively. Adults consumed an estimated 13.15 mg during anthesis. 4 The relevance of our results to ecological risk assessment of transgenic insecticidal corn and predator life history strategies is discussed. The results presented here are a first attempt to quantify pollen consumption by a predator, and future areas of research are suggested.     

The effect of flowering calendula and cuphea plants on Orius insidiosus survival and predation of Aphis glycines

Flowering oilseed crops have the potential to diversify agroecosystems currently dominated by corn and soybeans and improve the provision of ecosystem services such as pest control. Nectar and pollen feeding may increase natural enemy fitness and searching behaviour, increasing their survival and prey consumption rates. The soybean aphid (Aphis glycines Matsumura; Hemiptera: Aphididae) is a particularly widespread and costly agricultural pest. In this study, we evaluate the effects of two flowering oilseed crops, cuphea and calendula, on the survival of the insidious flower bug (Orius insidiosus Say; Hemiptera: Anthocoridae) and its consumption levels of A. glycines placed on soybean plants. We also evaluated the survival of O. insidiosus when placed on glandular and non-glandular cuphea varieties. The amount of A. glycines that remained unconsumed by O. insidiosus did not differ among treatments. Because mortality levels of O. insidiosus were higher on glandular compared to non-glandular cuphea plants, glandular trichomes, or plant hairs, may play a role in impeding movement and prey consumption by O. insidious.     

Genomic Modifiers of Natural Killer Cells,Immune Responsiveness and Lymphoid Tissue Remodeling Together Increase Host Resistance to Viral Infection

The MHC class I D^k molecule supplies vital host resistance during murine cytomegalovirus (MCMV) infection. Natural killer (NK) cells expressing the Ly49G2 inhibitory receptor, which specifically binds D^k, are required to control viral spread. The extent of D^k-dependent host resistance, however, differs significantly amongst related strains of mice, C57L and MA/My. As a result, we predicted that relatively small-effect modifier genetic loci might together shape immune cell features, NK cell reactivity, and the host immune response to MCMV. A robust D^k-dependent genetic effect, however, has so far hindered attempts to identify additional host resistance factors. Thus, we applied genomic mapping strategies and multicolor flow cytometric analysis of immune cells in naive and virus-infected hosts to identify genetic modifiers of the host immune response to MCMV. We discovered and validated many quantitative trait loci (QTL); these were mapped to at least 19 positions on 16 chromosomes. Intriguingly, one newly discovered non-MHC locus (Cmv5) controlled splenic NK cell accrual, secondary lymphoid organ structure, and lymphoid follicle development during MCMV infection. We infer that Cmv5 aids host resistance to MCMV infection by expanding NK cells needed to preserve and protect essential tissue structural elements, to enhance lymphoid remodeling and to increase viral clearance in spleen.     

Catabolic enzyme activities in the pectoralis muscle of premigratory and migratory juvenile Reed Warblers Acrocephalus scirpaceus (Herm.)

Summary Differences in catabolic capacity in the pectoralis major muscle of premigratory and migratory Reed Warblers were examined. The oxidative capacity was greater in the migratory birds, probably reflecting a training effect caused by the increased locomotion activity just prior to migration.Fatty acid oxidation was already high in the premigratory birds, possibly reflecting a saving of carbohydrate for anabolic purposes (feather growth) during the moult. Glycolytic capacity was slightly increased in the migratory birds, suggesting an increased carbohydrate oxidation during migration in spite of the great contribution of fatty acid oxidation.     

Cardiac performance in humans during breath holding

The effects on cardiac performance of high and low intrathoracic pressures induced by breath holding at large and small lung volumes have been investigated. Cardiac index and systolic time intervals were recorded from six resting subjects with impedance cardiography in both the nonimmersed and immersed condition. A thermoneutral environment (air 28 degrees C, water 35 degrees C) was used to eliminate the cold-induced circulatory component of the diving response. Cardiac performance was enhanced during immersion compared with nonimmersion, whereas it was depressed by breath holding at large lung volume. The depressed performance was apparent from the decrease in cardiac index (24.1% in the immersed and 20.9% in the nonimmersed condition) and from changes in systolic time intervals, e.g., shortening of left ventricular ejection time coupled with lengthening of preejection period. In the absence of the cold water component of the diving response, breath holding at the large lung volume used by breath-hold divers tends to reduce cardiac performance presumably by impeding venous return.