Mating type and the genetic basis of self-fertility in the model fungus Aspergillus nidulans

Sexual reproduction occurs in two fundamentally different ways: by outcrossing, in which two distinct partners contribute nuclei, or by self-fertilization (selfing), in which both nuclei are derived from the same individual. Selfing is common in flowering plants, fungi, and some animal taxa. We investigated the genetic basis of selfing in the homothallic fungus Aspergillus nidulans. We demonstrate that alpha and high-mobility group domain mating-type (MAT) genes, found in outcrossing species, are both present in the genome of A. nidulans and that their expression is required for normal sexual development and ascospore production. Balanced overexpression of MAT genes suppressed vegetative growth and stimulated sexual differentiation under conditions unfavorable for sex. Sexual reproduction was correlated with significantly increased expression of MAT genes and key genes of a pheromone-response MAP-kinase signaling pathway involved in heterothallic outcrossing. Mutation of a component MAP-kinase mpkB gene resulted in sterility. These results indicate that selfing in A. nidulans involves activation of the same mating pathways characteristic of sex in outcrossing species, i.e., self-fertilization does not bypass requirements for outcrossing sex but instead requires activation of these pathways within a single individual. However, unlike heterothallic species, aspects of pheromone signaling appeared to be independent of MAT control.     

Synthesis of novel antitumoural analogues of dysidiolide from ent-halimic acid

Several sesterterpenolides analogues of dysidiolide have been synthesized and their in vitro antitumoural activity against human HeLa, A549, HT-29 and HL-60 carcinoma cells is presented. The proliferation inhibition data showed a significant antitumour activity of the compounds 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5, inhibiting proliferation of distinct cancer cell types with an IC(50) in the low micromolar range.     

Biological and structural characterization of new linear gomesin analogues with improved therapeutic indices

Gomesin (Gm) is a potent antimicrobial peptide isolated from the spider Acanthoscurria gomesiana. The two disulfide bridges Cys(2,15) and Cys(6,11) facilitate the folding of the molecule in a beta-hairpin structure, conferring on the peptide a high stability in human plasma. We report herein biological and structural features of new linear Gm analogues, obtained by combining the removal of both disulfide bridges and the incorporation of a D- or L-proline. Regarding their biological properties, two analogues, namely, [D-Thr(2,6,11,15), Pro(9)]-D-Gm and [Thr(2,6,11,15), D-Pro(9)]-Gm, are as potent as Gm against Candida albicans and only fourfold less against Staphylococcus aureus and Escherichia coli. In addition, at 100 microM they are approximately threefold less hemolytic than Gm. The best therapeutic indices were found for [D-Thr(2,6,11,15), Pro(9)]-D-Gm and for [(Des-pGlu(1), -Thr(2), -Arg(3)), Thr(6,11,15), D-Pro(9)]-Gm with a 32-fold increase of their activity against bacteria, and from 128- to 512-fold against yeast when compared with Gm. Regarding the stability, [D-Thr(2,6,11,15), Pro(9)]-D-Gm appeared to be the most resistant in human serum, along with [D-Thr(2,6,11,15), Pro(8)]-D-Gm and [Thr(2,6,11,15), D-Arg(4,16), D-Pro(9)]-Gm. When evaluating their conformation by CD spectroscopy in sodium dodecyl sulfate (SDS), most linear analogues display beta-conformation characteristics. Moreover, considering its high therapeutic index and stability in serum, [D-Thr(2,6,11,15), Pro(9)]-D-Gm was further analyzed by NMR spectroscopy. (1)H NMR experiments in SDS micelles demonstrated that [D-Thr(2,6,11,15), Pro(9)]-D-Gm presents a conformation very similar to that of Gm. In our search for Gm analogues with enhanced potential for drug development, we demonstrated that designing cysteine-free analogues can improve the therapeutic index of Gm derivatives.     

Effect of ruthenium complexes on the activities of succinate dehydrogenase and cytochrome oxidase

In this article, we report the effects of acute administration of ruthenium complexes, trans-[RuCl(2)(nic)(4)] (nic=3-pyridinecarboxylic acid) 180.7 micromol/kg (complex I), trans-[RuCl(2)(i-nic)(4)] (i-nic=4-pyridinecarboxylic acid) 13.6 micromol/kg (complex II), trans-[RuCl(2)(dinic)(4)] (dinic=3,5-pyridinedicarboxylic acid) 180.7 micromol/kg (complex III) and trans-[RuCl(2)(i-dinic)(4)]Cl (i-dinic=3,4-pyridinedicarboxylic acid) 180.7 micromol/kg (complex IV) on succinate dehydrogenase (SDH) and cytochrome oxidase (COX) activities in brain (hippocampus, striatum and cerebral cortex), heart, skeletal muscle, liver and kidney of rats. Our results showed that complex I inhibited SDH activity in hippocampus, cerebral cortex, heart and liver; and inhibited COX in heart and kidney. Complex II inhibited SDH in heart and hippocampus; COX was inhibited in hippocampus, heart, liver and kidney. SDH activity was inhibited by complex III in heart, muscle, liver and kidney. However, COX activity was increased in hippocampus, striatum, cerebral cortex and kidney. Complex IV inhibited SDH activity in muscle and liver; COX activity was inhibited in kidney and increased in hippocampus, striatum and cerebral cortex. In a general manner, the complexes tested in this work decrease the activities of SDH and COX in heart, skeletal muscle, liver and kidney. In brain, complexes I and II were shown to be inhibitors and complexes III and IV activators of these enzymes. In vitro studies showed that the ruthenium complexes III and IV did not alter COX activity in kidney, but activated the enzyme in hippocampus, striatum and cerebral cortex, suggesting that these complexes present a direct action on COX in brain.     

Do antheridiogens act via gametophyte size? A study of Woodwardia radicans (Blechnaceae)

For many plants, sex is not fixed by genotype but determined by environmental conditions during development. In homosporous pteridophytes, sex is environmentally determined by the presence or absence of antheridiogens, maleness-inducing pheromones. It has been proposed that antheridiogens primarily reduce growth rate, with small gametophyte size responsible for maleness. To test this hypothesis, the effects of antheridiogen and intergametophytic competition on gender expression and gametophyte size were studied in a culture experiment with Woodwardia radicans. We found that (1) antheridiogen inhibited growth of gametophytes; and (2) slow growth favored maleness, whereas fast growth favored femaleness, irrespective of the presence or absence of antheridiogen. Both conclusions are consistent with the hypothesis that, in W. radicans, antheridiogen effect is mediated by size. They also agree with the "size-advantage" hypothesis in which energetic limitations associated with relatively small individual size impose a less severe limitation for male reproductive success than for female reproductive success. The results are also discussed with regard to a genetic sex-determining pathway that has recently been identified.     

Role of sialic acid in bovine sperm-zona pellucida binding

Sperm binding activity has been detected in zona pellucida (ZP) glycoproteins and it is generally accepted that this activity resides in the carbohydrate moieties. In the present study we aim to identify some of the specific carbohydrate molecules involved in the bovine sperm-ZP interaction. We performed sperm binding competition assays, in vitro fecundation (IVF) in combination with different lectins, antibodies and neuraminidase digestion, and chemical and cytochemical analysis of the bovine ZP. Both MAA lectin recognising alpha-2,3-linked sialic acid and neuraminidase from Salmonella typhimurium with catalytic activity for alpha-2,3-linked sialic acid, demonstrated a high inhibitory effect on the sperm-ZP binding and oocyte penetration. These results suggest that bovine sperm-ZP binding is mediated by alpha-2,3-linked sialic acid. Experiments with trisaccharides (sialyllactose, 3'-sialyllactosamine and 6'-sialyllactosamine) and glycoproteins (fetuin and asialofetuin) corroborated this and suggest that at least the sequence Neu5Ac(alpha2-3)Gal(beta1-4)GlcNAc is involved in the sperm-ZP interaction. Moreover, these results indicate the presence of a sperm plasma membrane specific protein for the sialic acid. Chemical analysis revealed that bovine ZP glycoproteins contain mainly Neu5Ac (84.5%) and Neu5GC (15.5%). These two types of sialic acid residues are probably linked to Galbeta1,4GlcNAc and GalNAc by alpha-2,3- and alpha-2,6-linkages, respectively, as demonstrated by lectin cytochemical analysis. The use of a neuraminidase inhibitor resulted in an increased number of spermatozoa bound to the ZP and penetrating the oocyte. From this last result we hypothesize that a neuraminidase from cortical granules would probably participate in the block to polyspermy by removing sialic acid from the ZP.     

Detection of Rubisco and mycotoxins as potential contaminants of a plantibody against the hepatitis B surface antigen purified from tobacco

Antibodies have been one of the proteins widely expressed in tobacco plants for pharmaceutical purposes, which demand contaminant free preparations. Rubisco constitutes 40-60% of tobacco leaf soluble proteins; therefore it is the major potential protein contaminant of plantibodies, while mycotoxins are toxic compounds that could be introduced during the biomass production and post-harvest stages with important consequences to human health. The objective of this paper was to investigate whether Rubisco and mycotoxins are present in Plantibody HB-01 preparations used in the immunopurification of the hepatitis B surface antigen. Rubisco was purified from Nicotiana tabacum yielding 154 microg of protein per gram of leaves and purity over 95%. Among mouse monoclonal antibodies generated against this enzyme, the CBSS.Rub-2 was selected for its immunodetection. It recognizes a conserved sequential epitope of Rubisco large subunit with an affinity constant of 0.13 x 10(8)M(-1). Rubisco quantification limit was 1 microg spreading to the measurement of this contaminant less than 4% of plantibodies samples. Additionally, according to a Reverse Phase-HPLC used to measure the level of adventitiously introduced contaminants, it can be concluded that aflatoxins B1, B2, G1 and G2 were undetected in the purified Plantibody HB-01 samples.     

Calorie restriction changes lipidomic profiles and maintains mitochondrial function and redox balance during isoproterenol-induced cardiac hypertrophy

Journal of Physiology and Biochemistry - Typically, healthy cardiac tissue utilizes more fat than any other organ. Cardiac hypertrophy induces a metabolic shift leading to a preferential...     

Reef‐building coralline algae from the Southwest Atlantic: filling gaps with the recognition of Harveylithon (Corallinaceae,Rhodophyta) on the Brazilian coast

The Southwest Atlantic is notable for having extensive reef areas cemented by nongeniculate coralline red algae. Based on an analysis of four genetic markers and morpho‐anatomical features, we clarify the species of Harveylithon in the tropical and warm temperate Southwest Atlantic. Species delimitation methods (mBGD, ABGD, SPN, and PTP), using three markers (psbA, rbcL, and COI), support the recognition of three new species: H. catarinense sp. nov., H. maris‐bahiensis sp. nov., and H. riosmenum sp. nov., previously incorrectly called Hydrolithon samoënse. Our findings highlight the importance of using an approach with several lines of evidence to solve the taxonomic status of the cryptic species.