Secondary conidium formation in Basidiobolus ranarum

1969 ◽  
Vol 53 (1) ◽  
pp. 132-137 ◽  
Author(s):  
A.A. Callaghan
Keyword(s):  
Conidium Formation ◽  
Secondary Conidium

The fine structure of conidium development in Phialocephala dimorphospora

1974 ◽  
Vol 52 (10) ◽  
pp. 2119-2128 ◽  
Author(s):  
George C. Carroll ◽  
Fanny E. Carroll
Keyword(s):  
Developmental Stages ◽  
Lateral Wall ◽  
The Body ◽  
Lipid Bodies ◽  
Dense Granules ◽  
Conidium Formation ◽  
Secondary Conidium ◽  
Apical Vesicles ◽  
Myelin Figures ◽  
Primary Conidium

Sequential developmental stages from synchronously sporulating cultures of Phialocephala dimorphospora Kendrick have been examined. Apical vesicles characterize growth of the primary conidium. These are not, however, seen during secondary conidium formation; instead, large vesicles containing minute membrane fragments develop just below the phialide neck and contribute to wall formation as they fuse with the plasmalemma. The occurrence of microtubules in the neck of the phialide is restricted to primary conidium formation. Just as the primary conidial initial begins to swell, electron-dense granules 50-75 nm in diameter arise in association with the plasmalemma. Such granules are not seen during secondary conidium formation; they are thought to be involved in pigment deposition in the collarette. During both primary and secondary conidium production the conidia go through a sequence of maturation in which the cytoplasm becomes very dense and contains lipid bodies and flocculent aggregations of electron-transparent granules. Subsequently the conidia become less electron dense and reveal a simple internal substructure consisting of a nucleus, mitochondria, micro-bodies, free ribosomes, and presumed storage bodies. The plasmalemma becomes convoluted in a network of interdigitated grooves. Septum formation occurs rapidly and involves the fusion of vesicles with the lateral wall. Mature septa are non-perforate. Although Woronin bodies have been repeatedly observed in young conidia, they are never seen in mature conidia. Myelin figures associated with mitochondria occur consistently in the body of the phialide during conidiation. These may be the source of the lipid bodies in the conidia. In phialides from cultures over 1 week old, signs of senescence are apparent. These include vacuolization of the upper portion of the phialide and the presence of many disorganized sheets of membrane. Spores still present within the collarette of such phialides are smaller than those produced early in the life of the phialide.

scholarly journals The Fungi-specific histone Acetyltransferase Rtt109 mediates morphogenesis, Aflatoxin synthesis and pathogenicity in Aspergillus flavus by acetylating H3K9

IMA Fungus ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ruilin Sun ◽  
Meifang Wen ◽  
Lianghuan Wu ◽  
Huahui Lan ◽  
Jun Yuan ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Histone Acetyltransferase ◽  
Epigenetic Modification ◽  
Aerial Mycelium ◽  
Environmental Stress Response ◽  
New Thought ◽  
Conidium Formation ◽  
Complementary Strain ◽  
And Control ◽  
Yeast Extract Sucrose

AbstractAspergillus flavus is a common saprophytic filamentous fungus that produces the highly toxic natural compound aflatoxin during its growth process. Synthesis of the aflatoxins, which can contaminate food crops causing huge losses to the agricultural economy, is often regulated by epigenetic modification, such as the histone acetyltransferase. In this study, we used Aspergillus flavus as an experimental model to construct the acetyltransferase gene rtt109 knockout strain (△rtt109) and its complementary strain (△rtt109·com) by homologous recombination. The growth of △rtt109 was significantly suppressed compared to the wild type (WT) strain and the △rtt109·com strain. The sclerotium of △rtt109 grew smaller, and the amount of sclerotia generated by △rtt109 was significantly reduced. The number of conidiums of △rtt109 was significantly reduced, especially on the yeast extract sucrose (YES) solid medium. The amount of aflatoxins synthesized by △rtt109 in the PDB liquid medium was significantly decreased We also found that the △rtt109 strain was extremely sensitive to DNA damage stress. Through the maize seed infection experiment, we found that the growth of △rtt109 on the surface of affected corn was largely reduced, and the amount of aerial mycelium decreased significantly, which was consistent with the results on the artificial medium. We further found that H3K9 was the acetylated target of Rtt109 in A. flavus. In conclusion, Rtt109 participated in the growth, conidium formation, sclerotia generation, aflatoxin synthesis, environmental stress response, regulation of infection of A. flavus. The results from this study of rtt109 showed data for acetylation in the regulation of life processes and provided a new thought regarding the prevention and control of A. flavus hazards.

A closed system of cytoplasmic variation in Aspergillus glaucus

1958 ◽  
Vol 148 (932) ◽  
pp. 355-359 ◽  
Keyword(s):  
Closed System ◽  
Nuclear Gene ◽  
Gene Segregation ◽  
Original Parent ◽  
Aspergillus Glaucus ◽  
Conidium Formation ◽  
Cytoplasmic Variation

A strain of the homothallic ascomycete Aspergillus glaucus was isolated from nature and found to produce sectors continually during subculturing (figure 25, plate 18). Sectors (here called the ' A ’ type) on certain media differ quantitatively from the original parent mycelium (the ‘ B ’ type) in at least five characters, the most easily observable being greatly enhanced conidium formation. When propagated asexually and sexually the ‘ A ’ and ‘ B ’ types behave in an unexpected manner (figure 24, observation, also Subak Sharpe 1956 a,b ). When subculturing from ‘ A ’ type is done with inocula of large overall cytoplasmic volume, that is, when colonies are started from hyphal tips, mycelium blocks or masses of either ascospores or conidia, then only ‘A ’ type colonies are formed.But when new cultures initiate from small cytoplasmic volumes, i.e. when conidial suspensions or ascospores from single perithecia are dilution plated, then some spores germinate to give ‘ A ’ colonies and the others ' B ' colonies. The relative proportions can vary greatly and depend on the parent colony’s medium, the age of the spores and other factors. Ascospore segregations from single perithecia actually frequently mimic 1:1 single nuclear gene segregation. (Ascospores of this strain are haploid and uninucleate in origin, conidia are binucleate in origin.)

CONIDIUM PRODUCTION OF VENTURIA INAEQUALIS IN SYNTHETIC CULTURE MEDIA

1974 ◽  
Vol 54 (1) ◽  
pp. 93-100 ◽  
Author(s):  
R. G. ROSS
Keyword(s):  
Filter Paper ◽  
Culture Media ◽  
Venturia Inaequalis ◽  
Conidium Production ◽  
Conidium Formation ◽  
Synthetic Media

Two isolates, 365-4 and 1096, and the five races of Venturia inaequalis were used to investigate the effects of various factors on conidium production on filter paper cylinders standing in liquid synthetic media. The isolates and races varied significantly in conidium production and there was a large variation among tests done on different days. Varying the concentration of conidia used as inoculum and the age of cultures from which the inoculum was derived did not affect conidium production. Making single conidium transfers every 6 mo did not consistently enhance conidium formation in all isolates and races. Conidium yields were optimum between 16 and 19 days at a temperature of 16 C. The concentrations of glucose, nitrogen, KH2PO4, and MgSO4 required for optimum conidium production were not critical.

Conidium Formation in Species of Aspergilli

Mycologia ◽  
1945 ◽  
Vol 37 (5) ◽  
pp. 582 ◽  
Author(s):  
Gladys E. Baker
Keyword(s):  
Conidium Formation

scholarly journals NsdC and NsdD Affect Aspergillus flavus Morphogenesis and Aflatoxin Production

2012 ◽  
Vol 11 (9) ◽  
pp. 1104-1111 ◽  
Author(s):  
Jeffrey W. Cary ◽  
Pamela Y. Harris-Coward ◽  
Kenneth C. Ehrlich ◽  
Brian M. Mack ◽  
Shubha P. Kale ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Strong Association ◽  
Aflatoxin Production ◽  
Expression Data ◽  
Aflatoxin Biosynthesis ◽  
Wild Type ◽  
Content Type ◽  
Conidium Formation ◽  
In The Wild ◽  
Type Gene

ABSTRACT The transcription factors NsdC and NsdD are required for sexual development in Aspergillus nidulans . We now show these proteins also play a role in asexual development in the agriculturally important aflatoxin (AF)-producing fungus Aspergillus flavus . We found that both NsdC and NsdD are required for production of asexual sclerotia, normal aflatoxin biosynthesis, and conidiophore development. Conidiophores in nsdC and nsdD deletion mutants had shortened stipes and altered conidial heads compared to those of wild-type A. flavus . Our results suggest that NsdC and NsdD regulate transcription of genes required for early processes in conidiophore development preceding conidium formation. As the cultures aged, the Δ nsdC and Δ nsdD mutants produced a dark pigment that was not observed in the wild type. Gene expression data showed that although AflR is expressed at normal levels, a number of aflatoxin biosynthesis genes are expressed at reduced levels in both nsd mutants. Expression of aflD , aflM , and aflP was greatly reduced in nsdC mutants, and neither aflatoxin nor the proteins for these genes could be detected. Our results support previous studies showing that there is a strong association between conidiophore and sclerotium development and aflatoxin production in A. flavus.

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