scholarly journals Prey element stoichiometry controls ecological fitness of the flagellate Ochromonas danica

2014 ◽  
Vol 71 (3) ◽  
pp. 257-269 ◽  
Author(s):  
TH Chrzanowski ◽  
BLL Foster
Keyword(s):  
Ecological Fitness ◽  
Ochromonas Danica

scholarly journals Transcription Factor STE12α Has Distinct Roles in Morphogenesis, Virulence, and Ecological Fitness of the Primary Pathogenic Yeast Cryptococcus gattii

2006 ◽  
Vol 5 (7) ◽  
pp. 1065-1080 ◽  
Author(s):  
Ping Ren ◽  
Deborah J. Springer ◽  
Melissa J. Behr ◽  
William A. Samsonoff ◽  
Sudha Chaturvedi ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Gene Knockout ◽  
Natural Habitat ◽  
Cryptococcus Gattii ◽  
Human Neutrophils ◽  
Knockout Mutant ◽  
Pathogenic Yeast ◽  
Ecological Fitness

ABSTRACT Cryptococcus gattii is a primary pathogenic yeast, increasingly important in public health, but factors responsible for its host predilection and geographical distribution remain largely unknown. We have characterized C. gattii STE12α to probe its role in biology and pathogenesis because this transcription factor has been linked to virulence in many human and plant pathogenic fungi. A full-length STE12α gene was cloned by colony hybridization and sequenced using primer walk and 3′ rapid amplification of cDNA ends strategies, and a ste12αΔ gene knockout mutant was created by URA5 insertion at the homologous site. A semiquantitative analysis revealed delayed and poor mating in ste12αΔ mutant; this defect was not reversed by exogenous cyclic AMP. C. gattii parent and mutant strains showed robust haploid fruiting. Among putative virulence factors tested, the laccase transcript and enzymatic activity were down regulated in the ste12αΔ mutant, with diminished production of melanin. However, capsule, superoxide dismutase, phospholipase, and urease were unaffected. Similarly, Ste12 deficiency did not cause any auxotrophy, assimilation defects, or sensitivity to a large panel of chemicals and antifungals. The ste12αΔ mutant was markedly attenuated in virulence in both BALB/c and A/Jcr mice models of meningoencephalitis, and it also exhibited significant in vivo growth reduction and was highly susceptible to in vitro killing by human neutrophils (polymorphonuclear leukocytes). In tests designed to simulate the C. gattii natural habitat, the ste12αΔ mutant was poorly pigmented on wood agar prepared from two tree species and showed poor survival and multiplication in wood blocks. Thus, STE12α plays distinct roles in C. gattii morphogenesis, virulence, and ecological fitness.

The effects of spectinomycin and ethidium bromide on the synthesis of organelle rRNA and on ultrastructure in Ochromonas danica

1980 ◽  
Vol 43 (1) ◽  
pp. 119-136
Author(s):  
H. Smith-Johannsen ◽  
D. Fromson ◽  
S.P. Gibbs
Keyword(s):  
Electron Microscopy ◽  
Ethidium Bromide ◽  
Ribosomal Proteins ◽  
Specific Inhibitor ◽  
Chloroplast Ultrastructure ◽  
Normal Amount ◽  
Chloroplast Membranes ◽  
Mitochondrial Ribosomes ◽  
Mitochondrial Rrna ◽  
Ochromonas Danica

The effects of 24-h exposure to spectinomycin (100 microgram/ml) and ethidium bromide (1 microgram/ml) on the accumulation of chloroplast and mitochondrial rRNAs and on organelle ultrastructure were studied in greening cells of Ochromonas danica. Cells treated with ethidium bromide for 24 h divide at the same rate as controls but contain less than one third the normal amount of mitochondrial rRNA. Ultrastructural observations showed that these cells contain only 10% the number of mitochondrial ribosomes found in controls as well as fewer mitochondrial cristae. Ethidium bromide has no effect on chloroplast ultrastructure in Ochromonas. Greening cells treated with spectinomycin grow at close to control rates but contain 30–40% less chloroplast rRNA than do controls. Electron microscopy showed that spectinomycin disrupts the organization of chloroplast membranes and reduces the number of chloroplast ribosomes by 30%. Under these conditions, spectinomycin has no effect on mitochondrial rRNA or ultrastructure. Since spectinomycin is a specific inhibitor of translation on 70S ribosomes, these results are consistent with the possibility that at least some chloroplast ribosomal proteins are synthesized in the chloroplast of Ochromonas.

The route of entry of cytoplasmically synthesized proteins into chloroplasts of algae possessing chloroplast ER

1979 ◽  
Vol 35 (1) ◽  
pp. 253-266
Author(s):  
S.P. Gibbs
Keyword(s):  
Protein Synthesis ◽  
Nuclear Envelope ◽  
Outer Membrane ◽  
Chloroplast Envelope ◽  
Inhibit Protein Synthesis ◽  
Ochromonas Danica ◽  
Plastid Proteins ◽  
Regular Network ◽  
Cytoplasmic Ribosomes ◽  
Plastid Ribosomes

In 8 classes of algae, namely the Cryptophyceae, Raphidophyceae, Haptophyceae, Chrysophyceae, Bacillariophyceae, Xanthophyceae, Eustigmatophyceae and Phaeophyceae, the chloroplasts, in addition to being surrounded by a double-membraned chloroplast envelope, are also enclosed by a cisterna of endoplasmic reticulum called the chloroplast ER. Often this ER cisterna is continuous with the outher membrane of the nuclear envelope in such a manner that the nuclear envelope forms a part of the ER sac enclosing the chloroplast. In all these classes of algae except the Cryptophyceae, a regular network of tubules and vesicles, named the periplastidal reticulum, is present at a specific location between the chloroplast envelope and the chloroplast ER. In the Cryptophyceae, scattered vesicles are found between the chloroplast envelope and the chloroplast ER. Ribosomes which have been shown to be arranged to polysomes are found on the outer membrane of the chloroplast ER. It is proposed that nuclear-coded proteins which are destined for the chloroplast are synthesized on these polysomes, passing during synthesis into the lumen of the ER cisterna. Vesicles containing these proteins then pinch off the chloroplast ER and form the periplastidal reticulum. Vesicles containing these proteins then pinch off the chloroplast ER and form the periplastidal reticulum. Vesicles then fuse with the outer membrane of the chloroplast envelope thereby delivering their contents to the lumen of the chloroplast envelope. Proteins then cross the inner membrane of the chloroplast envelope in an as yet unknown manner. Experimental evidence for this hypothesis comes from studies on Ochromonas danica using chloramphenicol and spectinomycin, which inhibit protein synthesis on plastid ribosomes, and cycloheximide, which inhibits protein synthesis on cytoplasmic ribosomes. In cells of Ochromonas exposed to chloramphenicol or spectinomycin, the periplastidal reticulum proliferates markedly becoming several layers thick. Presumably this build up of periplastidal reticulum occurs because the transport of cytoplasmically synthesized plastid proteins is slowed down when protein synthesis in the chloroplast is inhibited. Conversely, when cells of Ochromonas are treated with cycloheximide, there is a reduction in the amount of periplastidal reticulum presumably because there are no cytoplasmically synthesized proteins to be transported into the chloroplast.

scholarly journals Using Chimeric Hypoviruses To Fine-Tune the Interaction between a Pathogenic Fungus and Its Plant Host

2000 ◽  
Vol 74 (16) ◽  
pp. 7562-7567 ◽  
Author(s):  
Baoshan Chen ◽  
Lynn M. Geletka ◽  
Donald L. Nuss
Keyword(s):  
Pathogenic Fungus ◽  
Cryphonectria Parasitica ◽  
Cdna Clones ◽  
Plant Host ◽  
Reading Frame ◽  
Ecological Fitness ◽  
Severe Strain ◽  
Fungal Isolates ◽  
Virulence Attenuation ◽  
Fine Tune

ABSTRACT Infectious cDNA clones of mild (CHV1-Euro7) and severe (CHV1-EP713) hypovirus strains responsible for virulence attenuation (hypovirulence) of the chestnut blight fungus Cryphonectria parasitica were used to construct viable chimeric viruses. Differences in virus-mediated alterations of fungal colony morphology, growth rate, and canker morphology were mapped to a region of open reading frame B extending from nucleotides 2,363 to 9,904. By swapping domains within this region, it was possible to generate chimeric hypovirus-infectedC. parasitica isolates that exhibited a spectrum of defined colony and canker morphologies. Several severe strain traits were observed to be dominant. It was also possible to uncouple the severe strain traits of small canker size and suppression of asexual sporulation. For example, fungal isolates infected with a chimera containing nucleotides 2363 through 5310 from CHV1-Euro7 in a CHV1-713 background formed small cankers that were similar in size to that caused by CHV1-EP713-infected isolates but with the capacity for producing asexual spores at levels approaching that observed for fungal isolates infected with the mild strain. These results demonstrate that hypoviruses can be engineered to fine-tune the interaction between a pathogenic fungus and its plant host. The identification of specific hypovirus domains that differentially contribute to canker morphology and sporulation levels also provides considerable utility for continuing efforts to enhance biological control potential by balancing hypovirulence and ecological fitness.

scholarly journals Gene Flow in Phaseolus Beans and Its Role as a Plausible Driver of Ecological Fitness and Expansion of Cultigens

2021 ◽  
Vol 9 ◽  
Author(s):  
María Isabel Chacón-Sánchez ◽  
Jaime Martínez-Castillo ◽  
Jorge Duitama ◽  
Daniel G. Debouck
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Time Perspective ◽  
Lima Bean ◽  
Breeding Systems ◽  
Large Contribution ◽  
Interspecific Gene Flow ◽  
Ecological Fitness ◽  
Technological Advances ◽  
Evolutionary Force

The genus Phaseolus, native to the Americas, is composed of more than eighty wild species, five of which were domesticated in pre-Columbian times. Since the beginning of domestication events in this genus, ample opportunities for gene flow with wild relatives have existed. The present work reviews the extent of gene flow in the genus Phaseolus in primary and secondary areas of domestication with the aim of illustrating how this evolutionary force may have conditioned ecological fitness and the widespread adoption of cultigens. We focus on the biological bases of gene flow in the genus Phaseolus from a spatial and time perspective, the dynamics of wild-weedy-crop complexes in the common bean and the Lima bean, the two most important domesticated species of the genus, and the usefulness of genomic tools to detect inter and intraspecific introgression events. In this review we discuss the reproductive strategies of several Phaseolus species, the factors that may favor outcrossing rates and evidence suggesting that interspecific gene flow may increase ecological fitness of wild populations. We also show that wild-weedy-crop complexes generate genetic diversity over which farmers are able to select and expand their cultigens outside primary areas of domestication. Ultimately, we argue that more studies are needed on the reproductive biology of the genus Phaseolus since for most species breeding systems are largely unknown. We also argue that there is an urgent need to preserve wild-weedy-crop complexes and characterize the genetic diversity generated by them, in particular the genome-wide effects of introgressions and their value for breeding programs. Recent technological advances in genomics, coupled with agronomic characterizations, may make a large contribution.

scholarly journals Cry1C rice doesn’t affect the ecological fitness of rice brown planthopper, Nilaparvata lugens either under RDV stress or not

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Xuefei Chang ◽  
Linlin Sun ◽  
Duo Ning ◽  
Cong Dang ◽  
Hongwei Yao ◽  
...  
Keyword(s):  
Brown Planthopper ◽  
Oviposition Preference ◽  
Nilaparvata Lugens ◽  
Commercial Production ◽  
Infection Status ◽  
Rice Dwarf Virus ◽  
Abiotic And Biotic Stress ◽  
Life Table Parameters ◽  
Ecological Fitness ◽  
Potential Risks

Abstract The potential risks of Bt rice on non-target arthropods (NTAs) should be evaluated and defined before commercial production. Recently, effects of Bt rice on NTAs under abiotic and biotic stress conditions attracted much attention. Here we reported the effects of Bt rice T1C-19 (Cry1C rice) on the non-target herbivore, Nilaparvata lugens (rice brown planthopper, BPH) with or without RDV (rice dwarf virus) infection conditions. BPH showed no feeding and oviposition preference between Bt rice T1C-19 and its non-Bt parental rice Minghui 63 (MH63), as well as between RDV-infected and RDV-free rice plants. Meanwhile, rice type, RDV infection status, and their interaction had little impacts on the survival, development and fecundity of BPH. By comparison with non-Bt control, Bt rice T1C-19 with or without RDV infection had no significant effects on the life-table parameters of BPH including rm, R0, T, DT and λ. Thus, it could be concluded that Bt rice T1C-19 doesn’t affect the ecological fitness of BPH either under RDV stress or not.

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