The veA gene is a key regulator governing morphogenetic development and secondary metabolism in many fungi. Here, we characterized and disrupted a veA orthologue in an ochratoxigenic Aspergillus ...niger strain. Morphological development, ochratoxin A (OTA) biosynthesis, and oxidative stress tolerance in the wild-type and veA disruption strains were further analyzed. Accordingly, the link between the veA gene and development of specific gene brlA, OTA biosynthesis key gene pks, and oxidative-stress-tolerance-related gene cat was explored. Results demonstrated that the veA gene acts as a positive regulator of conidia production, OTA biosynthesis, and oxidative stress tolerance in A. niger, regardless of light conditions. Darkness promoted conidial production and OTA biosynthesis in the A. niger wild-type strain. Our results contribute to a better understanding of the veA regulatory mechanism and suggest the veA gene as a potential target for developing control strategies for A. niger infection and OTA biosynthesis.
Summary
Two conserved 14‐3‐3 proteins orthologous to Saccharomyces cerevisiae Bmh1/2 are poorly understood in filamentous fungi. Here we show that Bmh1 and Bmh2 contribute equally to the fundamental ...biology and physiology of Beauveria bassiana by targeting many sets of proteins/enzymes. Single Bmh deletion caused similar upregulation of another. Excellent knockdown (∼91%) expressions of Bmh1 in ΔBmh2 and Bmh2 in ΔBmh1 resulted in equally more severe multiphenotypic defects than the single deletions, including G2/M transition, blastospore size, carbon/nitrogen utilization, conidiation, germination and conidial tolerances to high osmolarity, oxidation, cell wall stress, high temperature and UV‐B irradiation. All the deletion and deletion/knockdown mutants showed similar defects in blastospore yield and density, hyphal septation and cell size, hyphal responses to most chemical stresses and virulence. All the defects were evident with altered transcripts of phenotype‐related genes and well restored by each Bmh complementation. Our Bmh1‐ and Bmh2‐specific transcriptomes generated under osmotic and oxidative stresses revealed up to 6% genes differentially expressed by at least twofold in the fungal genome. Many of those were greatly depressed or co‐depressed in ΔBmh1 and ΔBmh2. Our findings provide a thorough insight into the functions and complementary effects of the two 14‐3‐3 proteins in the filamentous entomopathogen.
Ferns (Pteridophyta) are very important members of the plant kingdom that lag behind other taxa with regards to our understanding of their genetics, genomics, and molecular biology. We report here, ...to our knowledge, the first instance of stable transformation of fern with recovery of transgenic sporophytes. Spores of the arsenic hyperaccumulating fern Pteris vittata and tetraploid 'C-fern Express' (Ceratopteris thalictroides) were stably transformed by Agrobacterium tumefaciens with constructs containing the P. vittata actin promoter driving a GUSPlus reporter gene. Reporter gene expression assays were performed on multiple tissues and growth stages of gametophytes and sporophytes. Southern-blot analysis confirmed stable transgene integration in recovered sporophytes and also confirmed that no plasmid from A. tumefaciens was present in the sporophyte tissues. We recovered seven independent transformants of P. vittata and four independent C. thalictroides transgenics. Inheritance analyses using β-glucuronidase (GUS) histochemical staining revealed that the GUS transgene was stably expressed in second generation C. thalictroides sporophytic tissues. In an independent experiment, the gusA gene that was driven by the 2× Cauliflower mosaic virus 35S promoter was bombarded into P. vittata spores using biolistics, in which putatively stable transgenic gametophytes were recovered. Transformation procedures required no tissue culture or selectable marker genes. However, we did attempt to use hygromycin selection, which was ineffective for recovering transgenic ferns. This simple stable transformation method should help facilitate functional genomics studies in ferns.
Despite the unique phenotypic properties and clinical importance of Penicillium marneffei, the polyketide synthase genes in its genome have never been characterized. Twenty-three putative polyketide ...synthase genes and two putative polyketide synthase nonribosomal peptide-synthase hybrid genes were identified in the P. marneffei genome, a diversity much higher than found in other pathogenic thermal dimorphic fungi, such as Histoplasma capsulatum (one polyketide synthase gene) and Coccidioides immitis (10 polyketide synthase genes). These genes were evenly distributed on the phylogenetic tree with polyketide synthase genes of Aspergillus and other fungi, indicating that the high diversity was not a result of lineage-specific gene expansion through recent gene duplication. The melanin-biosynthesis gene cluster had gene order and orientations identical to those in the Talaromyces stipitatus (a teleomorph of Penicillium emmonsii) genome. Phylogenetically, all six genes of the melanin-biosynthesis gene cluster in P. marneffei were also most closely related to those in T. stipitatus, with high bootstrap supports. The polyketide synthase gene of the melanin-biosynthesis gene cluster (alb1) in P. marneffei was knocked down, which was accompanied by loss of melanin pigment production and reduced ornamentation in conidia. The survival of mice challenged with the alb1 knockdown mutant was significantly better than those challenged with wild-type P. marneffei (P < 0.005). The sterilizing doses of hydrogen peroxide, leading to a 50% reduction in survival of conidia, were 11 min for wild-type P. marneffei and 6 min for the alb1 knockdown mutant of P. marneffei, implying that the melanin-biosynthesis gene cluster contributed to virulence through decreased susceptibility to killing by hydrogen peroxide.
Aegerolysins are small secreted pore-forming proteins that are found in both prokaryotes and eukaryotes. The role of aegerolysins in sporulation, fruit body formation, and in lysis of cellular ...membrane is suggested in fungi. The aim of the present study was to characterize the biological function of the aegerolysin gene
agl1
in the mycoparasitic fungus
Trichoderma atroviride
, used for biological control of plant diseases. Gene expression analysis showed higher expression of
agl1
during conidiation and during growth in medium supplemented with cell wall material from the plant pathogenic fungus
Rhizoctonia solani
as the sole carbon source. Expression of
agl1
was supressed under iron-limiting condition, while
agl1
transcript was not detected during
T
.
atroviride
interactions with the prey fungi
Botrytis cinerea
or
R
.
solani
. Phenotypic analysis of
agl1
deletion strains (Δ
agl1
) showed reduced conidiation compared to
T
.
atroviride
wild type, thus suggesting the involvement of AGL1 in conidiation. Furthermore, the Δ
agl1
strains display reduced antagonism towards
B. cinerea
and
R
.
solani
based on a secretion assay, although no difference was detected during direct interactions. These data demonstrate the role of AGL1 in conidiation and antagonism in the mycoparasitic fungus
T
.
atroviride
.
Recent surveys of belowground fungal biodiversity in México and USA have revealed many undescribed truffle species, including many in the genus Tuber. Here we describe seven new species: Tuber ...beyerlei, T. castilloi, T. guevarai, T. lauryi, T. mexiusanum, T. miquihuanense and T. walkeri. Phy-logenetic analyses place these species within the Maculatum group, an understudied clade of small truffles with little apparent economic value. These species are among the more taxonomically challenge-ing in the genus. We collected Tuber castilloi, T. mexiusanum and T. guevarai as fruit bodies and ectomycorrhizae on Quercus spp. in forests of eastern México. Tuber mexiusanum has a particularly broad geographic range, being collected in eastern USA under Populus deltoides and in Minnesota and Iowa in mixed hardwood forests. T. walkeri is described from the upper midwestern USA, and T. lauryi and T. beyerlei occur in the western USA.
Paracoccidioidomycosis is a systemic mycosis caused by Paracoccidioides brasiliensis (species S1, PS2, PS3), and Paracoccidioides lutzii. This work aimed to differentiate species within the genus ...Paracoccidioides, without applying multilocus sequencing, as well as to obtain knowledge of the possible speciation processes.
Single nucleotide polymorphism analysis on GP43, ARF and PRP8 intein genes successfully distinguished isolates into four different species. Morphological evaluation indicated that elongated conidia were observed exclusively in P. lutzii isolates, while all other species (S1, PS2 and PS3) were indistinguishable. To evaluate the biogeographic events that led to the current geographic distribution of Paracoccidioides species and their sister species, Nested Clade and Likelihood Analysis of Geographic Range Evolution (LAGRANGE) analyses were applied. The radiation of Paracoccidioides started in northwest South America, around 11-32 million years ago, as calculated on the basis of ARF substitution rate, in the BEAST program. Vicariance was responsible for the divergence among S1, PS2 and P. lutzii and a recent dispersal generated the PS3 species, restricted to Colombia. Taking into account the ancestral areas revealed by the LAGRANGE analysis and the major geographic distribution of L. loboi in the Amazon basin, a region strongly affected by the Andes uplift and marine incursions in the Cenozoic era, we also speculate about the effect of these geological events on the vicariance between Paracoccidioides and L. loboi.
The use of at least 3 SNPs, but not morphological criteria, as markers allows us to distinguish among the four cryptic species of the genus Paracoccidioides. The work also presents a biogeographic study speculating on how these species might have diverged in South America, thus contributing to elucidating evolutionary aspects of the genus Paracoccidioides.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
A social behavior named cannibalism has been described during the early stages of sporulation of the Gram-positive Bacillus subtilis. This phenomenon is based on the heterogeneity of ...sporulating populations, constituted by at least two cell types: (1) sporulating cells, in which the master regulator of sporulation Spo0A is active, and (2) nonsporulating cells, in which Spo0A is inactive. Sporulating cells produce two toxins that act cooperatively to kill the nonsporulating sister cells. The nutrients released by the dead cells into the starved medium are used for growth by the sporulating cells that are not yet fully committed to sporulate, and as a result, sporulation is arrested. This review outlines the molecular mechanisms of the killing and immunity to the toxins, the regulation of their production and other examples of killing of siblings in microorganisms. The biological significance of this behavior is discussed.
Bacillus probiotics Cutting, Simon M.
Food microbiology,
04/2011, Letnik:
28, Številka:
2
Journal Article, Conference Proceeding
Recenzirano
Bacterial spore formers are being used as probiotic supplements for use in animal feeds, for human dietary supplements as well as in registered medicines. Their heat stability and ability to survive ...the gastric barrier makes them attractive as food additives and this use is now being taken forward. While often considered soil organisms this conception is misplaced and Bacilli should be considered as gut commensals. This review summarises the current use of
Bacillus species as probiotics, their safety, mode of action as well as their commercial applications.
Anthrax, a disease caused by Bacillus anthracis, affects animals and humans. Because the inert spore is the infectious form of the organism that first contacts the potential host, the interaction ...between the host and spore exosporium is vital to the initiation of disease. Here, we demonstrate that the integrin Mac-1 is essential for the recognition of the major exosporium protein BclA by phagocytic cells. Expression of Mac-1, but not p150/95, in CHO cells markedly enhanced infection with Sterne strain of B. anthracis spores (WT spores). Conversely, CD11b⁻/⁻ macrophages demonstrated a significant decrease in spore uptake when compared with macrophages from normal C57BL/6 mice. However, when CD11b⁻/⁻ macrophages were infected with ΔbclA spores, spore ingestion was no different from their C57BL/6 counterparts. ΔbclA spores were also efficiently internalized by all CHO cell lines tested, independently of Mac-1 expression. Taken together, these results show that there is an alternative Mac-1-independent pathway involved in spore uptake that is unmasked only in the absence of BclA. Survival studies, using C57BL/6 and CD11b⁻/⁻ mice, revealed that CD11b⁻/⁻ mice are more resistant to infection with WT but not ΔbclA spores. Our experiments also show that ΔbclA spores are more virulent than WT spores in C57BL/6 and A/J mice. Overall, our data indicate that the Mac-1/BclA interaction may play a major role in B. anthracis pathogenesis by promoting spore uptake by professional phagocytes and subsequent access to a favorable niche for transport, germination, and outgrowth in lymphoid tissues.
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