• Korean Journal of Poultry Science
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• v.19 no.3
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• pp.161-176
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• 1992

Coccidiosis is caused by Eimeria infecting primarily the intestine of the susceptible host, thereby seriously impairing the growth and feed utilization of livestock and poultry. The genus Eimeria contains a number of obligate intracellular protozoan parasites with a complicated life-cycle involving both asexual and sexual stages of development. The desire to develop a vaccine against Eimeria has Promoted active research to elucidate the mechanisms of protective immunity and identification of candidate vaccine antigens. Protozoa are unique in their modes of transmission and nature of disease manifestations, the significance of which should be considered in the development of a control strategy. An intricate and complex interplay of different cell populations and cytokines is involved not only in the pathogenesis of coccidiosis but also in the development of protective immunity Thus, comprehensive understanding of the events leading to protection following Eimeria infection will be crucial for the development of an effective vaccine.

• Mycobiology
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• v.50 no.6
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• pp.467-474
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• 2022

Autophagy serves as a survival mechanism and plays important role in nutrient recycling under conditions of starvation, nutrient storage, ad differentiation of plant pathogenic fungi. However, autophagy-related genes have not been investigated in Colletotrichum scovillei, a causal agent of pepper fruit anthracnose disease. ATG8 is involved in autophagosome formation and is considered a marker of autophagy. Therefore, we generated an ATG8 deletion mutant, ΔCsatg8, via homologous recombination to determine the functional roles of CsATG8 in the development and virulence of C. scovillei. Compared with the wild-type, the deletion mutant ΔCsatg8 exhibited a severe reduction in conidiation. Conidia produced by ΔCsatg8 were defective in survival, conidial germination, and appressorium formation. Moreover, conidia of ΔCsatg8 showed reduced lipid amount and PTS1 selectivity. A virulence assay showed that anthracnose development on pepper fruits was reduced in ΔCsatg8. Taken together, our results suggest that CsATG8 plays various roles in conidium production and associated development, and virulence in C. scovillei.

• Journal of Plant Biotechnology
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• v.44 no.3
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• pp.320-324
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• 2017

Development of modern agricultural machinery and accompanying agricultural development cause soil compaction and reduce growth by stressing roots. Kalanchoe pinnata was used to investigate the impact of stress on rooting and changes in plant growth and reproduction. K. pinnata forms somatic embryos capable of asexual reproduction at the edge of leaves. Impact of root pressurization of K. pinnata on somatic embryogenesis and organ differentiation according to external stress factors was investigated by using a high concentration of agar and this phenomenon was studied histologically. Agar concentration in culture media ranged from 0.5%-1.5% to induce a compression effect on roots. The stem and leaf of K. pinnata were subjected to a microtechnique process to study changes in tissue. In vivo, K. pinnata produced 2nd and 3rd plantlets at edges of leaves from lack of water and excessive lighting conditions. In in vitro culture studies, the lower the concentration of agar, the higher the population and the higher the biomass, but plantlet did not occur in leaf bends. Conversely, as concentration of agar increased, increase in the number of individuals was low. Plantlet development occurred only in agar 1.5% medium. The difference in agar concentration was a stressor in the root of K. pinnata, and thus the pattern of asexual reproduction changed from the division method in root to a plantlet generation in leaf. This suggests root pressurization may act as stress and change in the plant reproduction pattern.

• 한국균학회소식:학술대회논문집
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• 2014.10a
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• pp.15-15
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• 2014

Fusarium graminearum (teleomorph Gibberella zeae) is an important plant pathogen that causes head blight of major cereal crops such as wheat, barley, and rice, as well as causing ear and stalk rot on maize worldwide. Plant diseases caused by this fungus lead to severe yield losses and accumulation of harmful mycotoxins in infected cereals [1]. Fungi utilize spore production as a mean to rapidly avoid unfavorable environmental conditions and to amplify their population. Spores are produced sexually and asexually and their production is precisely controlled. Upstream developmental activators consist of fluffy genes have been known to orchestrate early induction of condiogenesis in a model filamentous fungus Aspergillus nidulans. To understand the molecular mechanisms underlying conidiogenesis in F. graminearum, we characterized functions of the F. graminearum fluffy gene homologs [2]. We found that FlbD is conserved regulatory function for conidiogenesis in both A. nidulans and F. graminearum among five fluffy gene homologs. flbD deletion abolished conidia and perithecia production, suggesting that FlbD have global roles in hyphal differentiation processes in F. graminearum. We further identified and functionally characterized the ortholog of AbaA, which is involved in differentiation from vegetative hyphae to conidia and known to be absent in F. graminearum [3]. Deletion of abaA did not affect vegetative growth, sexual development, or virulence, but conidium production was completely abolished and thin hyphae grew from abnormally shaped phialides in abaA deletion mutants. Overexpression of abaA resulted in pleiotropic defects such as impaired sexual and asexual development, retarded conidium germination, and reduced trichothecene production. AbaA localized to the nuclei of phialides and terminal cells of mature conidia. Successful interspecies complementation using A. nidulans AbaA and the conserved AbaA-WetA pathway demonstrated that the molecular mechanisms responsible for AbaA activity are conserved in F. graminearum as they are in A. nidulans. F. graminearum ortholog of Aspergillus nidulans wetA has been shown to be involved in conidiogenesis and conidium maturation [4]. Deletion of F. graminearum wetA did not alter mycelial growth, sexual development, or virulence, but the wetA deletion mutants produced longer conidia with fewer septa, and the conidia were sensitive to acute stresses, such as oxidative stress and heat stress. Furthermore, the survival rate of aged conidia from the F. graminearum wetA deletion mutants was reduced. The wetA deletion resulted in vigorous generation of single-celled conidia through autophagy-dependent microcycle conidiation, indicating that WetA functions to maintain conidia dormancy by suppressing microcycle conidiation in F. graminearum. In A. nidulans, FlbB physically interacts with FlbD and FlbE, and the resulting FlbB/FlbE and FlbB/FlbD complexes induce the expression of flbD and brlA, respectively. BrlA is an activator of the AbaA-WetA pathway. AbaA and WetA are required for phialide formation and conidia maturation, respectively [5]. In F. graminearum, the AbaA-WetA pathway is similar to that of A. nidulans, except a brlA ortholog does not exist. Amongst the fluffy genes, only fgflbD has a conserved role for regulation of the AbaA-WetA pathway.

• Mycobiology
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• v.38 no.4
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• pp.229-237
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• 2010

Members of the genus Aspergillus are the most common fungi and all reproduce asexually by forming long chains of conidiospores (or conidia). The impact of various Aspergillus species on humans ranges from beneficial to harmful. For example, several species including Aspergillus oryzae and Aspergillus niger are used in industry for enzyme production and food processing. In contrast, Aspergillus flavus produce the most potent naturally present carcinogen aflatoxins, which contaminate various plant- and animal-based foods. Importantly, the opportunistic human pathogen Aspergillus fumigatus has become the most prevalent airborne fungal pathogen in developed countries, causing invasive aspergillosis in immunocompromised patients with a high mortality rate. A. fumigatus produces a massive number of small hydrophobic conidia as the primarymeans of dispersal, survival, genome-protection, and infecting hosts. Large-scale genome-wide expression studies can now be conducted due to completion of A. fumigatus genome sequencing. However, genomics becomes more powerful and informative when combined with genetics. We have been investigating the mechanisms underlying the regulation of asexual development (conidiation) and gliotoxin biosynthesis in A. fumigatus, primarily focusing on a characterization of key developmental regulators identified in the model fungus Aspergillus nidulans. In this review, I will summarize our current understanding of how conidiation in two aspergilli is regulated.

• Mycobiology
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• v.33 no.2
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• pp.69-76
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• 2005

Conidial development of Cordyceps militaris was observed from germinating ascospores and vegetative hyphae through light and scanning electron microscopy (SEM). Ascospores were discharged from fresh specimens of C. militaris in sterile water as well as Sabouraud Dextrose agar plus Yeast Extract (SDAY) plates. We observed ascospore germination and conidial formation periodically. Under submerged condition in sterile water, most part-spores germinated unidirectionally and conidia were developed directly from the tips of germinating hyphae of part-spores within 36 h after ascospore discharge, showing microcyclic conidiation. First-formed conidia were cylindrical or clavate followed by globose and ellipsoidal ones. Germination of ascospores and conidial development were observed on SDAY agar by SEM. Slimy heads of conidia on variously arranged phialides, from solitary to whorl, developed 5 days after ascospore discharge. Besides, two distinct types of conidia, elongated pyriform or cylindrical and globose, were observed in the same slimy heads by SEM. Conidia were shown to be uninucleate with 4,6-diamidino-2-phenylindole staining. Conidiogenous cells were more slender than vegetative hyphae, having attenuated tips. Microcyclic conidiation, undifferentiated conidiogenous hyphae (phialides), polymorphic conidia and solitary, opposite to whorled type of phialidic arrangement are reported here as the characteristic features of asexual stage of C. militaris, which can be distinguished from other Cordyceps species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.6
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• pp.393-398
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• 2005

Codium fragile is commercially farmed in Korea by natural blooming zygote attachment. Experiments found optimum conditions for artificial seed production and nursery culture of C. fragile by asexual reproduction. Isolated utricles and medullary filaments were regenerated to erect thalli using both indoor and outdoor culture experiments. Under the indoor culture conditions, irradiance was an important factor to control the development of erect thalli. Formation of erect thallus from the isolated medullary filaments in the indoor culture was induced after 30 days under $20^{\circ}C$ and $60{\mu}mol/m^2/sec$. The detachment of isolated utricles and medullary filaments from the substrates of seed strings was reduced by exposure to the air during 2 hrs before the indoor culture of seed strings. The maximum growth and development of erect thalli in the nursery culture was induced at a water depth of 0.5 m. Depending on the substrates of the seed strings the growth of erect thalli was not significantly different (p>0.05).

• Journal of Microbiology
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• v.44 no.2
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• pp.145-154
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• 2006

Heterotrimeric G proteins (G proteins) are conserved in all eukaryotes and are crucial components sensing and relaying external cues into the cells to elicit appropriate physiological and biochemical responses. Basic units of the heterotrimeric G protein signaling system include a G protein-coupled receptor (GPCR), a G protein composed of ${\alpha},\;{\beta},\;and\;{\gamma}$ subunits, and variety of effectors. Sequential sensitization and activation of these G protein elements translates external signals into gene expression changes, resulting in appropriate cellular behaviors. Regulators of G protein signaling (RGSs) constitute a crucial element of appropriate control of the intensity and duration of G protein signaling. For the past decade, G protein signaling and its regulation have been intensively studied in a number of model and/or pathogenic fungi and outcomes of the studies provided better understanding on the upstream regulation of vegetative growth, mating, development, virulence/pathogenicity establishment, and biosynthesis of secondary metabolites in fungi. This review focuses on the characteristics of the basic upstream G protein components and RGS proteins, and their roles controlling various aspects of biological processes in the model filamentous ascomycete fungus Aspergillus nidulans. In particular, their functions in controlling hyphal proliferation, asexual spore formation, sexual fruiting, and the mycotoxin sterigmatocystin production are discussed.

• Journal of Microbiology
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• v.43 no.6
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• pp.523-528
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• 2005

Using the genomic library constructed at the downstream of the niiA promoter, which induces the over-expression of an inserted DNA fragment, we have attempted to screen the genes affecting growth or development by over-expression. The wild-type strain was transformed using the AMA-niiA(p) library and cultured on 1.2 M sorbitol media, in which asexual sporulation is induced, but sexual development is repressed. Over 100,000 strains transformed to $pyrG^+$ were analyzed with regard to any changes in phenotype. Consequently, seven strains were isolated for further analyses. These strains were designated NOT [niiA(p) over-expression transformants] stains. Four of the strains were of the inducible type, and the remaining strains were of the multi-copy suppression type. Two of the inducible-type strains, NOT 1 and NOT40, harbored genes which had been inserted in reverse direction, suggesting that the mutant phenotypes had been derived from an excess amount of anti-sense mRNA. Domain analyses of the deduced polypeptides from the DNA fragments rescued from the transformants revealed that NOT1, NOT40 and NOT6 harbored a LisH motif, a forkhead domain, and a $Zn(II)_2Cys_6$ binuclear zinc cluster, respectively.

• Parasites, Hosts and Diseases
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• v.48 no.1
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• pp.23-33
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• 2010

An understanding of the nature of the immune response to asexual erythrocytic stages of malaria parasites will facilitate vaccine development by identifying which responses the vaccine should preferentially induce. The present study examined and compared the immune responses of NIH mice in either single or mixed infections with avirulent (DK) or virulent (DS) strains of Plasmodium chabaudi adami using the ELISA test for detecting and measurement of cytokines and antibody production. In both single and mixed infections, the study showed that both cell- and antibody-mediated responses were activated. In all experiments, an early relatively high level of IFN-$\gamma$ and IgG2a during the acute phase of the infection, and later elevation of IL-4 and IgG1, suggested that there was a sequential Th1/Th2 response. However, in the avirulent DK strain infection a stronger Th1 response was observed compared to the virulent DS strain-infection or in mixed infections. In the virulent DS infection, there was a stronger Th2 response compared to that in the DK and mixed infections. The faster proliferation rate of the virulent DS strain compared to the DK strain was also evident.