• Title, Summary, Keyword: sporulation

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Genetic Control of Asexual Sporulation in Fusarium graminearum

  • Son, Hokyoung;Kim, Myung-Gu;Chae, Suhn-Kee;Lee, Yin-Won
    • 한국균학회소식:학술대회논문집
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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.

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Occurrence of Bunch Rot Disease Caused by Aspergillus tubingensis on Shine Muscat Grape (Aspergillus tubingensis에 의한 샤인머스켓 포도송이썩음병(가칭)의 발생)

  • Kim, Young Soo;Kwon, Hyeok Tae;Hong, Seung-Beom;Jeon, Yongho
    • Research in Plant Disease
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    • v.25 no.4
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    • pp.220-225
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    • 2019
  • During the year 2018, the symptoms of bunch rot on Shine Muscat (Vitis vinifera L.) were observed in Kimcheon-si, Gyeongbuk province in Korea. The disease appears on the Shine Muscat as a black rot due to prolific fungal sporulation after it has invaded into the Shine Muscat which look completely empty and dryness. Colonies of these fungi are present on the Shine Muscat skin from fruit setting and increase in amount from early season to harvest, while become peak at ripening stage. To isolate the causal agent, small fragments (2 to 3 mm) of decayed tissue from the lesion margin were placed onto potato dextrose agar (PDA) plates. Fungal colonies on PDA produced dense white aerial mycelium and then covered with dark black conidial heads. These heads were large and radiate, and vesicles were globose (2.12-32.0×2.0-3.1 ㎛). Based on morphological and cultural characteristics, this fungus was identified as Aspergillus tubingensis. To confirm its identity, the internal transcribed spacer, β-tubulin, and RNA polymerase II was sequenced for molecular identification. BLAST search indicated 99% identity with A. tubingensis. The pathogenicity test on healthy grape of Shine Muscat produced bunch rot, as the original symptoms. To select effective fungicides for the control of brunch rot, an in vitro antifungal activity of seven fungicides were evaluated against the growth of A. tubingensis. Five fungicides (dipenoconazole, tebuconazole, metconazole, iminoctadine, and captan) exhibited significantly strong suppression of the mycelial growth of A. tubingensis.

Studies on the Mutation of Aspergillus niger (흑국균(黑麴菌)의 인공변이(人工變異)에 관(關)한 연구(硏究))

  • Park, Yoon-Joong;Sohn, Cheon-Bae
    • Korean Journal of Food Science and Technology
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    • v.14 no.1
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    • pp.72-79
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    • 1982
  • Several mutants were isolated from the parent strain of Aspergillus niger CF: the first mutant strain CF-11 was obtained by UV irradiation, and the second mutant strain CF-21 and CF-22 were from NTG (N-methyl-N'-nitroso-N-nitroso-guanidine) treatment on the CF-11. These mutants were characterized, and their enzyme and acid production on wheat bran Koji and wheat flour Koji were studied. Asp. niger CF-22 mutant appeared to be tan type which conidial heads were discolored. It's glucoamylase activity was inreased approximately two times and its ${\alpha}-amylase$ about 50 percent as compared with that of the parent strain of Asp. niger CF, when grown on wheat bran Koji under the optimal conditions. Asp. niger CF-21 mutant showed slower growth rate and poor sporulation than the wild type, although its conidial heads were not discolored. Approximately 4-fold increment in its acid production was observed as compared with the weld type. The activities of glucoamylase and ${\alpha}-amylase$ of the Asp. niger CF-22 and CF-21 mutants were higher than those of the wild type, but their protease activity was rather lower. The maximum production of glucoamylase by the Asp. niger CF-22 mutant was obtained after 2 to 3 days incubation on wheat bran at 30 to $35^{\circ}C;$ ${\alpha}-amylase$2 days incubation at 30 to $35^{\circ}C$. The maximal levels of acid production by the mutant CF-21 was appeared after 2 days incubation on wheat bran Koji, and after 3 days on wheat flour Koji at $30^{\circ}C$. Little differences in the levels of acid production were observed between on wheat bran and flour Koji.

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Study on Marteilioides chungmuensis Comps et al., 1986 Parasite of the Pacific Oyster, Crassostrea gigas Thunberg (참굴의 난(卵)에 기생(寄生)하는 Marteilioids chungmuensis Comps et al., 1986에 관하여)

  • Park, Mi-Seon;Chun, Seh-Kyu
    • Journal of fish pathology
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    • v.2 no.2
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    • pp.53-70
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    • 1989
  • An ovarian parasite, Marteilioides chungmuensis of the Pacific oyster, Crassostrea gigas has been observed on several occasions in the Pacific sector of production of this oyster species(Matsuzato et al., 1977 ; Chun, 1979). This study was carried out on the specimens collected at Hwado, Och'$\check{o}$n, and Sinchang respectively located the southern, western, and eastern coasts of Korean Peninsula from 1986 through 1988 to investigate M. chungmuensis to the Pacific oyster. Uitrastructural studies were also carried out on infected oysters, to allow detailed examination of the structure and consepuently the systematic position of this parasite. Infection rates of M. chungmuensis at Hwado and Och'$\check{o}$n oyster farms were 5.3% and 4.2% each in 1986, 6.7% and 2.8% each in 1987, but they were not found at Sinchang oyster habitat. M,. chungmuensis-infected oysters were found from June to November at Hwado and from June to October at Och'$\check{o}$n. Twenty five of three hundred oysters transplanted from Sinchang to Hwado were found infected with M. chungmuensis. Some abnormal eggs infected with M. chungmuensis are liberated through the gill together with normal mature eggs on the spawning and the rest remain necrotized after spawning season. The earliest known stages consist of a stem cell or primary cell, including a secondary cell in which ovoid haplosporosomes are found. During sporulation, 2 or 3 secondary are produced by exogenous budding from the first secondary cell and, each secondary cell evolves into a sporont upon the tertiary cell differentiation (enodogenous budding) ; then, haplosporosomes are formed in the young sporont. Internal cleavages involve the differentiation of one tricellular spore per sporont. The outermost spore cell contains membrane-bounded osmiophilic bodies : the middle and the inner, most spore cells contain high density cytoplasmic ribosomes. The mechanism of spore formation from the stem cell of M. chungmuensis is the simplest of the class Paramyxea known up to now.

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Effects of Various Physical and Chemical Factors on the Death of Trouble Seaweed Ulva australis (구멍갈파래(Ulva australis) 해조류 사멸에 미치는 여러 물리화학적 요인들의 영향)

  • Kim, Jin-Seog;Kwak, Hwa Sook;Kim, Bo Gwan
    • Weed & Turfgrass Science
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    • v.6 no.3
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    • pp.222-234
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    • 2017
  • Green tides, which was mainly caused by Ulva spp., have been increasing in severity and frequency globally, and have negatively affected on marine ecosystems. This study was conducted to investigate effects of various physical and chemical factors on the death of Ulva australis (ULAUS) and to consider a practical measures useful for alleviating Ulva bloom. Soaking of ULAUS thalli in pure water for 8 hr didn't induce a death, but incubation in 1.0-1.5% salinity for 7 d inhibited sporulation by about 70%. Desiccation gave rise to a serious damage when more than 40-50% of initial fresh weight was lost. ULAUS growth was sensitive to temperature and seriously inhibited from more than $30^{\circ}C$. At $35^{\circ}C$, $40^{\circ}C$, $45^{\circ}C$ and $50^{\circ}C$, treatment time required for 90-95% death of ULAUS thalli was 1 d, 10 min, 30 sec, and 1 sec, repectively. ULAUS growth was seriously inhibited at lower than pH 6.0 and completely dead at pH 4.0. Several compounds for ULAUS control was selected and the chemcals causing a rapid death were oxidants such as hydrogen peroxide and sodium percarbonate. Taken together, our results suggest that low salinities, dryness, pH, high temp. and compounds could be selected for Ulva bloom control, and high temperature and compounds seems to be useful for a development of practical control methods.

Effect of Scrapping Aerial Mycelia and Light on the Production of Macroconidia and Chlamydospores of Cylindrocarpon destructans Causing Root Rot of Panax ginseng (기중균사 제거와 광처리가 인삼 뿌리썩음병균 Cylindrocarpon destructans의 대형분생포자 및 후막포자 생성에 미치는 영향)

  • Cho Dae-Hui;Yu Yun-Hyun;Ohh Seung-Hwan
    • Journal of Ginseng Research
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    • v.23 no.3
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    • pp.123-129
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    • 1999
  • Under the light condition of 25,000 Lux (12 hrs dark and light cycle) with scrapping treatment of aerial mycelia of Cylindrocarpon destructans on potato dextrose agar (PDA), V-8 juice agar, and ginseng extract agar, production of the macroconidia was increased to $3.7\~8.1$ fold over them produced in the dark. They were also produced $7.7\~18.0$ times more in the liquid cultures under the light condition than under the dark as well. PDA and V-8 juice agar among the tested were the best for the macroconidium production. On PDA, 1,585 $macroconidia/mm^2$ were produced under the light of 25,000 Lux with scrapping treatment of aerial mycelia of C. destructans, which is 3.2 and 1.4 times more than those produced under 3,000 and 10,000 Lux, respectively. Meanwhile, $20\~99$ macroconidia/$mm^2$ were produced by the non-scrapping under the light condition between 3,000 Lux and 25,000 Lux. The macroconidia were, however, lysed at $6\~7$ days after being incubated under the above range of the light. They were consisted of $1\~3$ cells in a macroconidium while $69.4\~100\%$ of them were the two-celled and the number did not seem to be affected by either the scrapping or the light. Production of chlamydospore converted from mycelia of C. destructans seemed to be promoted by the light and the scrapping as well. The 1,285 chlamydospres/$mm^2$ were produced with the light (25,000 Lux), which is 2.8 and 1.2 times more than those with 3,000 and 10,000 Lux, respectively. Scrapping the aerial mycelia of the cultures increased the chlamydospore formation to 1.9, 2.5 and 1.4 times more than the non-scrapping under the light intensity of 3,000 Lux, 10,000 Lux, and 25,000 Lux, respectively. On PDA, 1 to 8 chlamydospore(s) per catena were formed by all treatments tested and $34.2\~58.9\%$ of them was a single chlamydospore, However, the numbers was affected by neither the light ($3,000\~25,000$ Lux) nor the scrapping the aerial mycelia.

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Laboratory-scale fruiting body formation of Pleurotus ostreatus using the petri dish culture (느타리의 기내 자실체 형성 및 그 유도조건에 관한 연구)

  • Joh, Joong-Ho;Chu, Kyo-Sun;Kim, Beom-Gi;Kong, Won-Sik;Yoo, Young-Bok;Lee, Seung-Jae;Cho, Bong-Gum;Lee, Chang-Soo
    • Journal of Mushroom
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    • v.2 no.1
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    • pp.15-20
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    • 2004
  • Pleurotus ostreatus, the oyster mushroom, is one of the most widely cultivated and important edible mushrooms in the world. In order to study the developmental process of P. ostreatus and its regulatory mechanism, a new culturing method needs to be established for inducing the fruiting body and sporulation in the laboratory. In this study, we have examined whether the fruiting body of P. ostreatus can be formed on the plastic petri dish which are commonly used for cell culture in the laboratory. The strain was cultured on $60{\times}15mm$ plastic petri dish with potato dextrose agar media at $28^{\circ}C$ for mycelial growth and then at $18^{\circ}C$ for the formation of primordia and fruiting bodies within plant growth chamber. The development of primordia into fruiting bodies was achieved on cultured dishes under air ventilation. At the primordia stage, the normal formation of fruiting body was blocked by sealing the plastic dish with parafilm. The periods requiring for the formation of primordia and fruiting bodies were examined on the dish culture. About 96% and 76% of cultured samples formed primordia and fruiting bodies under the optimal conditions during ten weeks of culture, respectively. These culturing periods, however, were changed by the mechanical injury treatment to mycelia. As other factors affecting the fruiting body formation, the effects of light and cold shock have been tested. No fruiting formation was observed on the cultured dishes under the dark. The cold shock treatment by storing cultured dishes for one day at $4^{\circ}C$ did not have any significant effects in the fruiting body formation. Spores of fruiting bodies acquired from the petri dishes could be germinated on culture media at $28^{\circ}C$. These results suggest that the fruiting bodies of P. ostreatus can be formed on the experimental petri dish and this dish-culturing method is useful for understanding of the developmental process of P. ostreatus in the laboratory. Furthermore, the dish-culturing method is able to shorten the life cycle of P. ostreatus without requiring large area and expensive device.

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