Phenotype responses to abiotic stresses, asexual reproduction and virulence among isolates of the entomopathogenic fungus Cordyceps javanica (Hypocreales: Cordycipitaceae).

Selecting entomopathogenic fungal isolates with resilience to environmental stresses, optimal mass production characteristics, and with high virulence to target pests favors the development of mycopesticides. A case in point, Cordyceps (= Isaria) javanica has been extensively investigated for non-chemical control of whiteflies worldwide. We phylogenetically characterized 11 native C. javanica isolates from Northeastern and Central Brazil. These isolates were screened for tolerance to heat-shock, UV-B radiation, osmotic and oxidative stresses, as well as conidial production on cereal grain and insecticidal activity against the whitefly Bemisia tabaci (MEAM 1) in the laboratory. All isolates were pathogenic to whiteflies and significant (3-fold) differences in median lethal concentration were observed among isolates. Furthermore, pronounced differences among isolates were found for stress factors and conidial production. Using principal component analysis, our results highlighted three major clusters formed by isolates (i) resistant to osmotic and oxidative stress, (ii) resilient to UV-B, and (iii) with high virulence, conidial production and heat tolerance. Overall, isolate CG1228 performed best based on multi-stress resistance, mass production and virulence attributes in the laboratory. This study highlights the importance of exploring natural variation in entomopathogenic fungi for selection of appropriate isolates for effective biocontrol of insect pests coupled with mass production characteristics and abiotic stress tolerances.

An injury-response mechanism conserved across kingdoms determines entry of the fungus Trichoderma atroviride into development.

A conserved injury-defense mechanism is present in plants and animals, in which the production of reactive oxygen species (ROS) and lipid metabolism are essential to the response. Here, we describe that in the filamentous fungus Trichoderma atroviride, injury results in the formation of asexual reproduction structures restricted to regenerating cells. High-throughput RNA-seq analyses of the response to injury in T. atroviride suggested an oxidative response and activation of calcium-signaling pathways, as well as the participation of lipid metabolism, in this phenomenon. Gene-replacement experiments demonstrated that injury triggers NADPH oxidase (Nox)-dependent ROS production and that Nox1 and NoxR are essential for asexual development in response to damage. We further provide evidence of H(2)O(2) and oxylipin production that, as in plants and animals, may act as signal molecules in response to injury in fungi, suggesting that the three kingdoms share a conserved defense-response mechanism.

When sex is not enough: ecological correlates of resprouting capacity in congeneric tropical forest shrubs.

In moist tropical forests resprouting may be an important component of life history, contributing to asexual reproduction through the clonal spread of individuals derived from shoot fragments. However, in contrast to other ecosystems where resprouting is common, the ecological correlates of resprouting capacity in tropical forests remain largely unexplored. In this study we characterized shade tolerance, resprouting capacity and sexual reproductive success of eight co-occurring Piper species from lowland forests of Panama. In field experiments we found that shade-tolerant Piper species had a higher capacity to regenerate from excised or pinned stem fragments than light-demanding species in both gap and understory light conditions. In contrast, shade-tolerant species had lower recruitment probabilities from seeds, as a consequence of lower initial seed viability, and lower seedling emergence rates. All Piper species needed gap conditions for successful seedling establishment. Of 8,000 seeds sown in the understory only 0.2% emerged. In gaps, seed germination of light-demanding species was between 10 and 50%, whereas for shade-tolerant species it was 0.5-9.8%. We propose that the capacity to reproduce asexually from resprouts could be adaptive for shade-tolerant species that are constantly exposed to damage from falling litter in the understory. Resprouting may allow Piper populations to persist and spread despite the high rate of pre-dispersal seed predation and low seed emergence rates. Across Piper species, we detected a trade-off between resprouting capacity and the annual viable seed production per plant but not with annual seed mass produced per plant. This suggests that species differences in sexual reproductive success may not necessarily result from differential resource allocation. Instead we suggest that low sexual reproductive success in the understory may in part reflect reduced genetic diversity in populations undergoing clonal growth, resulting in self-fertilization and in-breeding depression.

Descrição histológica da via genital masculina e hermafrodita de escargots das espécies Achatina fulica E Achatina monochromatica / Histology description of the male and hermafrodite genital vias of the escargots Achatina fulica AND Achatina monochromatica

O objetivo deste trabalho foi descrever a histologia da via genital masculina e hermafrodita dos escargots das espécies Achatina fulica e Achatina monochromatica. Foram usados 10 exemplares adultos de cada espécie para análise histológica. Após o processo seletivo, pesagem e tomada das medidas da concha, os espécimes foram sacrificados por congelamento em freezer, a -2ºC por aproximadamente 10min. Para a exposição dos órgãos reprodutores foi efetuada uma incisão longitudinal iniciada na extremidade cranial e, acompanhando a torção do corpo, até a extremidade caudal. Cada animal foi dissecado, sobre uma placa de Petri, sob imersão em formol a 10% para melhor preservação dos tecidos. Foram coletados fragmentos representativos de cada segmento do sistema reprodutor e observou-se que a estrutura histológica dos mesmos não apresentou diferenças notórias, com exceção do ovotestis do Achatina fulica, no qual se constatou um número maior de células pigmentadas no epitélio germinativo do que, nesse mesmo epitélio, no Achatina monochromatica.

The aim of this work was to make histological description of the male and hermaphrodite genital system of escargots of the species Achatina fulica and Achatina monochromatica. Ten adult copies of each species were used for such analysis. After a selective process, weighting and measuring the shell, the specimens were sacrificed by freezing in freezer to -2ºC for approximately 10min. Reproductive organs were exposed by longitudinal incision made in the cranial extremity and by accompanying the sprain of the body, until the tail extremity. Each animal was dissected over a Petri plate, under immersion in 10% phormol for better preservation of the tissues. Representative fragments of each segment of the reproductive system were collected and it was observed that their histological structure did not present evident differences, except for the Achatina fulica ovotestis in which a larger number of pigmented cells was observed in the germinative epithelium than in the same epithelium in the Achatina monochromatica.

Descrição histológica da via genital masculina e hermafrodita de escargots das espécies Achatina fulica e Achatina monochromatica / Histology description of the male and hermafrodite genital vias of the escargots Achatina fulica and Achatina monochromatica

O objetivo deste trabalho foi descrever a histologia da via genital masculina e hermafrodita dos escargots das espécies Achatina fulica e Achatina monochromatica. Foram usados 10 exemplares adultos de cada espécie para análise histológica. Após o processo seletivo, pesagem e tomada das medidas da concha, os espécimes foram sacrificados por congelamento em freezer, a -2ºC por aproximadamente 10min. Para a exposição dos órgãos reprodutores foi efetuada uma incisão longitudinal iniciada na extremidade cranial e, acompanhando a torção do corpo, até a extremidade caudal. Cada animal foi dissecado, sobre uma placa de Petri, sob imersão em formol a 10% para melhor preservação dos tecidos. Foram coletados fragmentos representativos de cada segmento do sistema reprodutor e observou-se que a estrutura histológica dos mesmos não apresentou diferenças notórias, com exceção do ovotestis do Achatina fulica, no qual se constatou um número maior de células pigmentadas no epitélio germinativo do que, nesse mesmo epitélio, no Achatina monochromatica.(AU)

The aim of this work was to make histological description of the male and hermaphrodite genital system of escargots of the species Achatina fulica and Achatina monochromatica. Ten adult copies of each species were used for such analysis. After a selective process, weighting and measuring the shell, the specimens were sacrificed by freezing in freezer to -2ºC for approximately 10min. Reproductive organs were exposed by longitudinal incision made in the cranial extremity and by accompanying the sprain of the body, until the tail extremity. Each animal was dissected over a Petri plate, under immersion in 10% phormol for better preservation of the tissues. Representative fragments of each segment of the reproductive system were collected and it was observed that their histological structure did not present evident differences, except for the Achatina fulica ovotestis in which a larger number of pigmented cells was observed in the germinative epithelium than in the same epithelium in the Achatina monochromatica.(AU)

Asexual recombination in a uvsH mutant of Aspergillus nidulans.

Mutations in the gene uvsH of Aspergillus nidulans result in increased spontaneous chromosome instability and increased intragenic and intergenic mitotic recombination in homozygous diploids. The aim of the present work was to obtain a uvs mutant of A. nidulans and to use it for the isolation of asexual recombinants (parameiotic segregants). The mutant uvsH, named B511, showed normal frequency of meiotic recombination in sexual crosses and high frequency of parameiotic segregants in the parasexual crossings with master strains (B511//A757 and B511//A288). Asexual haploid recombinants (parameiotic segregants), diploid and aneuploid segregants were recovered directly from the uvs//uvs+ heterokaryons (B511//A757 and B511// A288). Parameiotic segregants originated through mitotic crossing-over and independent assortment of chromosomes.

Asexual Recombination in a uvsH Mutant of Aspergillus nidulans

Mutations in the gene uvsH of Aspergillus nidulans result in increased spontaneous chromosome instability and increased intragenic and intergenic mitotic recombination in homozygous diploids. The aim of the present work was to obtain a uvs mutant of A. nidulans and to use it for the isolation of asexual recombinants (parameiotic segregants). The mutant uvsH, named B511, showed normal frequency of meiotic recombination in sexual crosses and high frequency of parameiotic segregants in the parasexual crossings with master strains (B511//A757 and B511//A288). Asexual haploid recombinants (parameiotic segregants), diploid and aneuploid segregants were recovered directly from the uvs//uvs+ heterokaryons (B511//A757 and B511// A288). Parameiotic segregants originated through mitotic crossing-over and independent assortment of chromosomes.

Parasexuality in asexual development mutants of Aspergillus nidulans.

The parasexual cycle with parameiosis has been characterized previously by the occurrence of genetic recombination and haploidization inside heterokaryotic hyphae prior to conidial formation. The aim of current research was to characterize, through genetic and cytological analyses, an asexual development mutant strain of A. nidulans and to use it to obtain parameiotic segregants. Analyses showed the medusa phenotype of the B84 strain, whose mutant allele was mapped in the chromosome I. The heterokaryons B84(med)//G422(med+) and B84(med)//G839(brl) were formed in liquid MM+2% CM and inoculated in the appropriate selective media. Two mitotic segregant groups were obtained: aneuploids and haploid stable recombinants. Mitotic segregants, wild-types, and developmental mutants, which did not produce new visible mitotic sectors in the presence of Benomyl and which showed normal meiotic behavior during the sexual cycle, were classified as parameiotics.

Parasexuality in asexual development mutants of Aspergillus nidulans

The parasexual cycle with parameiosis has been characterized previously by the occurrence of genetic recombination and haploidization inside heterokaryotic hyphae prior to conidial formation. The aim of current research was to characterize, through genetic and cytological analyses, an asexual development mutant strain of A. nidulans and to use it to obtain parameiotic segregants. Analyses showed the medusa phenotype of the B84 strain, whose mutant allele was mapped in the chromosome I. The heterokaryons B84(med)//G422(med+) and B84(med)//G839(brl) were formed in liquid MM+2% CM and inoculated in the appropriate selective media. Two mitotic segregant groups were obtained: aneuploids and haploid stable recombinants. Mitotic segregants, wild-types, and developmental mutants, which did not produce new visible mitotic sectors in the presence of Benomyl and which showed normal meiotic behavior during the sexual cycle, were classified as parameiotics.

Timing of fission in the starfish Allostichaster capensis (Echinodermata: Asteroidea) in laboratory

Timing of fission in the fissiparous starfish Allostichaster capensis under laboratory conditions is described. A. capensis generally splits across the disc along the fission plane during the spring, and then each half regenerates the missing arms during the rest of the year. The fission process can last eight hours. The healing process starts immediately after fission. A. capensis has impressive regeneration ability, including a comet, without signs of disc, regenerated two new arms

Polyembryony and apomixis in Eriotheca pubescens (Malvaceae - Bombacoideae).

Apomixis and adventitious polyembryony have been reported for several species of Bombacoideae, including Eriotheca pubescens, a tree species of the Neotropical savanna (Cerrado) areas in Brazil. However, the origin of polyembryonic seeds and their importance for the reproduction of the species remained to be shown. Here, we analyzed the early embryology of this species to establish the apomictic origin of extranumerary embryos. We also observed the geographic distribution of polyembryony in E. pubescens, and tested if apomixis was related to the source of pollen (self or cross) and population density. Moreover, we tested if polyembryonic apomictic embryos would develop normally into seedlings. In the observed seed primordia, after a relatively long quiescent period, the zygote developed into a sexual embryo concurrently with adventitious apomictic embryos which developed from nucellus cells. Adventitious embryos develop faster than sexual ones and are morphologically similar, so that 44 days after anthesis it was virtually impossible to distinguish and trace the fate of the sexual embryo. Polyembryony is widely distributed in populations some 400 km distant, and only one strictly monoembryonic individual was observed during the study. The number of embryos per seed varied between fruits and individuals but was significantly higher in seeds from cross-pollinations than from selfs, although fruit and seed set after crosses were much lower than after selfs. Embryo development into seedlings depended on their weight at germination, but polyembryonic seeds germinated and produced up to seven seedlings per seed in greenhouse conditions. Adventitious embryony and apomictic seedlings would explain the mostly clonal populations suggested by molecular studies.

Evidence for a monophyletic origin of triploid clones of the Amazon molly, Poecilia formosa.

Asexual reproduction in vertebrates is rare and generally considered an evolutionary dead end. Asexuality is often associated with polyploidy, and several hypotheses have been put forward to explain this relationship. So far, it remains unclear whether polyploidization in asexual organisms is a frequent or a rare event. Here we present a field study on the gynogenetic Amazon molly, Poecilia formosa. We used multilocus fingerprints and microsatellites to investigate the genetic diversity in 339 diploid and 55 triploid individuals and in 25 P. mexicana, its sexual host. Although multilocus DNA fingerprints found high clonal diversity in triploids, microsatellites revealed only two very similar clones in the triploids. Phylogenetic analysis of microsatellite data provided evidence for a monophyletic origin of the triploid clones of P. formosa. In addition, shared alleles within the triploid clones between the triploid and diploid genotypes and between asexual and sexual lineages indicate a recent origin of triploid clones in Poecilia formosa.

Timing of fission in the starfish Allostichaster capensis (Echinodermata: Asteroidea) in laboratory.

Timing of fission in the fissiparous starfish Allostichaster capensis under laboratory conditions is described. A. capensis generally splits across the disc along the fission plane during the spring, and then each half regenerates the missing arms during the rest of the year. The fission process can last eight hours. The healing process starts immediately after fission. A. capensis has impressive regeneration ability, including a comet, without signs of disc, regenerated two new arms.

In vitro segmentation induction of Mesocestoides corti (Cestoda) tetrathyridia.

Mesocestoides corti is a suitable model for studying cestode development because of its ability to reproduce asexually and segment in vitro. The cultured parasite is also capable of sexual differentiation and, probably, reproduction. To establish conditions that increase the efficiency of in vitro M. corti larvae (tetrathyridia) segmentation, we tested the effects of an inducing agent and some physical parameters in cultures. We found that a 5% CO2-95% N2 gas phase, an incubation temperature of 39 C (instead of 37 C), and a 24-hr pretreatment with trypsin (10(5) BAEE/ml, BAEE = Na-benzoil-L-arginine ethyl ester unit of trypsin activity) in Roswell Park Memorial Institute (RPMI) 1640 medium supplemented with 20% fetal bovine serum (FBS) are able to increase individually or synergistically the segmentation rate of tetrathyridia. A segmentation rate of up to 100% was achieved on day 4 of culture, when all these conditions were used simultaneously, in comparison with an average rate of 40% obtained not before day 11 in cultures without any inducing treatment. Fetal bovine serum is essential for segmentation, and a concentration of 20% was established as the standard for induction.

Asexual reproduction and molecular systematics of the sea anemone Anthopleura krebsi (Actiniaria: Actiniidae).

In this paper we use allozyme analyses to demonstrate that individuals in Anthopleura krebsi aggregates are monoclonal. Additionally, sympatric samples of the red and the green colour-morphs of A. krebsi from Pernambuco, Brazil were genetically compared and no significant differences were observed between them (gene identity = 0.992), indicating that they do not belong to different biological species. All individuals within aggregates of the green colour-morph were found to be identical over the five polymorphic loci analysed. Such results would be extremely unlikely (P < 10(-11)) if the individuals analysed had been generated through sexual reproduction, thus confirming the presence of asexual reproduction in this species.

Computer simulations for biological aging and sexual reproduction.

The sexual version of the Penna model of biological aging, simulated since 1996, is compared here with alternative forms of reproduction as well as with models not involving aging. In particular we want to check how sexual forms of life could have evolved and won over earlier asexual forms hundreds of million years ago. This computer model is based on the mutation-accumulation theory of aging, using bits-strings to represent the genome. Its population dynamics is studied by Monte Carlo methods.

Computer simulations for biological aging and sexual reproduction

The sexual version of the Penna model of biological aging, simulated since 1996, is compared here with alternative forms of reproduction as well as with models not involving aging. In particular we want to check how sexual forms of life could have evolved and won over earlier asexual forms hundreds of million years ago. This computer model is based on the mutation-accumulation theory of aging, using bits-strings to represent the genome. Its population dynamics is studied by Monte Carlo methods

Características biológicas de claviceps paspali stev & hall / Biological characteristics of claviceps paspali stev & hall

Se estudia el ciclo biológico de claviceps paspali, un ascomycete parásito, altamente específico de gramíneas del género paspalum (pasto miel). Desarrolla un ciclo asexual (sphacelia deliquescens) en el interior de las flores del pasto miel y uno sexual, en la superficie del suelo. El primero, comienza con la llegada de las ascosporas a la flor, que germina desarrollando un micelio y una secreción melosa muy rica en conidios, con el tiempo ésta se transforma en una masa esclerotial. El segundo se inicia con la germinación del esclerocio, dando 2 a 4 cabezuelas estromáticas, en cuyo interior se encuetran peritecios que contienen ascos con 8 ascosporas, las cuales son expulsadas activamente y los insectos las transportan nuevamente a la flor, cerrándo así el ciclo. La fase asexual es la encargada de la difusión masiva del hongo y la sexual de mantener el hongo viable hasta el verano siguiente

Ecology and life history of an amoebomastigote, Paratetramitus jugosus, from a microbial mat: new evidence for multiple fission.

Five microbial habitats (gypsum crust, gypsum photosynthetic community, Microcoleus mat, Thiocapsa scum, and black mud) were sampled for the presence of the euryhaline, rapidly growing amoebomastigote, Paratetramitus jugosus. Field investigations of microbial mats from Baja California Norte, Mexico, and Salina Bido near Matanzas, Cuba, reveal that P. jugosus is most frequently found in the Thiocapsa layer of microbial mats. Various stages of the life history were studied using phase-contrast, differential-interference, and transmission electron microscopy. Mastigote stages were induced and studied by electron microscopy; mastigotes that actively feed on bacteria bear two or more undulipodia. A three-dimensional drawing of the kinetid ("basal apparatus") based on electron micrographs is presented. Although promitoses were occasionally observed, it is unlikely that they can account for the rapid growth of P. jugosus populations on culture media. Dense, refractile, spherical, and irregular-shaped bodies were seen at all times in all cultures along with small mononucleate (approximately 2-7 micrometers diameter) amoebae. Cytochemical studies employing two different fluorescent stains for DNA (DAPI, mithramycin) verified the presence of DNA in these small bodies. Chromatin-like material seen in electron micrographs within the cytoplasm and blebbing off nuclei were interpreted to the chromatin bodies. Our interpretation, consistent with the data but not proven, is that propagation by multiple fission of released chromatin bodies that become small amoebae may occur in Paratetramitus jugosus. These observations are consistent with descriptions of amoeba propagules in the early literature (Hogue, 1914).