Beauveria bassiana (Bals.-Criv.) Vuill. is a valuable biological control agent for insects. B. bassiana efficacy can be influenced by plant interactions, including secondary metabolites, but the ...range of interactions with maize are not well understood. B. bassiana-treated sweet corn leaf tissue that had been fed on by fall armyworms, Spodoptera frugiperda (J.E. Smith), caused a significantly higher rate of mortality compared to leaf tissue provided to fall armyworms immediately after fungal treatment. These results suggest the ability of B. bassiana to interact with plant tissue should also be considered in selecting strains for commercial development.
The phenylpropanoid pathway in plants synthesizes a variety of structural and defence compounds, and is an important target in efforts to reduce cell wall lignin for improved biomass conversion to ...biofuels. Little is known concerning the trade-offs in grasses when perturbing the function of the first gene family in the pathway, PHENYLALANINE AMMONIA LYASE (PAL). Therefore, PAL isoforms in the model grass Brachypodium distachyon were targeted, by RNA interference (RNAi), and large reductions (up to 85%) in stem tissue transcript abundance for two of the eight putative BdPAL genes were identified. The cell walls of stems of BdPAL-knockdown plants had reductions of 43% in lignin and 57% in cell wall-bound ferulate, and a nearly 2-fold increase in the amounts of polysaccharide-derived carbohydrates released by thermochemical and hydrolytic enzymic partial digestion. PAL-knockdown plants exhibited delayed development and reduced root growth, along with increased susceptibilities to the fungal pathogens Fusarium culmorum and Magnaporthe oryzae. Surprisingly, these plants generally had wild-type (WT) resistances to caterpillar herbivory, drought, and ultraviolet light. RNA sequencing analyses revealed that the expression of genes associated with stress responses including ethylene biosynthesis and signalling were significantly altered in PAL knocked-down plants under non-challenging conditions. These data reveal that, although an attenuation of the phenylpropanoid pathway increases carbohydrate availability for biofuel, it can adversely affect plant growth and disease resistance to fungal pathogens. The data identify notable differences between the stress responses of these monocot pal mutants versus Arabidopsis (a dicot) pal mutants and provide insights into the challenges that may arise when deploying phenylpropanoid pathway-altered bioenergy crops.
Plant resistance factors, such as secondary metabolites and proteins, are known to affect the viability of insect fungal pathogens. Different plant varieties can have different levels of plant ...pathogen resistance, which could potentially influence efficacy of insect pathogens. Leaves from twelve maize (Zea mays L.) inbreds with different reported resistance to Fusarium and/or Aspergillus pathogens were examined for their influence on the efficacy of two different commercial strains of Beauveria bassiana (Bals.-Criv.) Vuill. against corn earworms, Helicovepa zea (Boddie) and fall armyworms, Spodoptera frugiperda (J.E. Smith). For leaf assays with first instar caterpillars, mortality on day 2 ranged from an inbred dependent high of 92% to a low of 14% for corn earworms, and from a high of 84% to a low of 22% for fall armyworms. Leaves that caused the greatest inhibition of B. bassiana efficacy had the greatest amount of caterpillar damage compared to corresponding control leaves that were not treated with B. bassiana. Damage ratings due to Fusarium graminearum (Schwabe) infection were often correlated with the mortality levels of both species of B. bassiana treated caterpillars that fed on leaves, suggesting that maize resistance factors to F. graminearum were interfering with the efficacy of B. bassiana. The study suggests that the interaction between plant pathogen resistance factors and insect pathogens should be considered when developing both new plant varieties and biocontrol strains that may be used for insect pest management where possible.
Use of microorganisms to manage insect pests is a strategy compatible with organic production, but variability in their effectiveness limits the adoption by growers. Prior reports indicated that ...increased resistance to a fungal plant pathogen in dent maize inbreds was associated with reduced efficacy of the commercialized fungal biocontrol agent
Beauveria bassiana
in killing maize caterpillar pests, but this aspect has not been investigated with sweet corn. Several varieties of sweet corn certified for organic production, along with sweet corn inbreds that have been used in breeding commercial sweet corn hybrids, were evaluated for their influence on the efficacy of two commercial strains of
Beauveria bassiana
. As occurred in prior dent corn studies, significant differences were noted in mortality levels on day 2 for European corn borers (ranging from as much as 14.9 to 58.6%) and fall armyworms (ranging from as much as 12.1 to 46.0%) depending on the sweet corn hybrids and inbreds. Higher rates of leaf colonization by
B. bassiana
were associated with larger lesion sizes caused by the maize pathogen
Fusarium graminearum
for both hybrids and inbreds. However, greater efficacy of
B. bassiana
in killing insects was associated with smaller lesion sizes caused by
F. graminearum
for some organic production sweet corn hybrids. This information indicates it is possible to develop sweet corn varieties that are both resistant to fungal pathogens and compatible with use of
B. bassiana
and suggests this aspect can be further improved to promote more effective organic production of sweet corn.
The coffee berry borer, Hypothenemus hampei, is the most economically important insect pest of coffee worldwide. We present an analysis of the draft genome of the coffee berry borer, the third genome ...for a Coleopteran species. The genome size is ca. 163 Mb with 19,222 predicted protein-coding genes. Analysis was focused on genes involved in primary digestion as well as gene families involved in detoxification of plant defense molecules and insecticides, such as carboxylesterases, cytochrome P450, gluthathione S-transferases, ATP-binding cassette transporters, and a gene that confers resistance to the insecticide dieldrin. A broad range of enzymes capable of degrading complex polysaccharides were identified. We also evaluated the pathogen defense system and found homologs to antimicrobial genes reported in the Drosophila genome. Ten cases of horizontal gene transfer were identified with evidence for expression, integration into the H. hampei genome, and phylogenetic evidence that the sequences are more closely related to bacterial rather than eukaryotic genes. The draft genome analysis broadly expands our knowledge on the biology of a devastating tropical insect pest and suggests new pest management strategies.
A Gram-stain positive, aerobic, motile, rod-shaped bacterium designated as strain CBP-2801
T
was isolated as a contaminant from a culture containing maize callus in Peoria, Illinois, United States. ...The strain is unique relative to other
Cohnella
species due to its slow growth and reduced number of sole carbon sources. Phylogenetic analysis using 16S rRNA indicated that strain CBP-2801
T
is a
Cohnella
bacterium and showed the highest similarity to
Cohnella xylanilytica
(96.8%). Genome-based phylogeny and genomic comparisons based on average nucleotide identity confirmed the strain to be a novel species of
Cohnella
. Growth occurs at 15–45 °C (optimum 40 °C), pH 5–7 (optimum pH 6) and with 0–1% NaCl. The predominant fatty acids are anteiso-15:0 and 18:1 ω6
c
. Genome mining for secondary metabolites identified a putative biosynthetic cluster that encodes for a novel lasso peptide. In addition, this study contributes five new genome assemblies of type strains of
Cohnella
species, a genus with less than 30% of the type strains sequenced. The DNA G + C content is 58.7 mol %. Based on the phenotypic, phylogenetic and biochemical data strain CBP-2801
T
represents a novel species, for which the name
Cohnella zeiphila
sp. nov. is proposed. The type strain is CBP-2801
T
(= DSM 111598 = ATCC TSD-230).
•An A. flavus hybrid PKS–NRPS produces a family of 2-pyridones, designated leporins.•First description of leporin production in A. flavus.•Leporin overproduction affects A. flavus development.•First ...description of leporin dimers and the leporin B trimer-iron complex.•A mechanism is proposed for the synthesis of leporins.
The genome of the filamentous fungus, Aspergillus flavus, has been shown to harbor as many as 56 putative secondary metabolic gene clusters including the one responsible for production of the toxic and carcinogenic, polyketide synthase (PKS)-derived aflatoxins. Except for the production of aflatoxins, cyclopiazonic acid and several other metabolites the capability for metabolite production of most of these putative clusters is unknown. We investigated the regulation of expression of the PKS–non-ribosomal peptide synthetase (NRPS) containing cluster 23 and determined that it produces homologs of the known 2-pyridone leporin A. Inactivation and overexpression of a cluster 23 gene encoding a putative Zn(2)-Cys(6) transcription factor (AFLA_066900, lepE) resulted in downregulation of nine and up-regulation of 8, respectively, of the fifteen SMURF-predicted cluster 23 genes thus allowing delineation of the cluster. Overexpression of lepE (OE::lepE) resulted in transformants displaying orange–red pigmented hyphae. Mass spectral analysis of A. flavus OE::lepE extracts identified the known 2-pyridone metabolite, leporin B, as well as the previously unreported dehydroxy-precursor, leporin C. We provide strong evidence that leporin B forms a unique trimeric complex with iron, not found previously for other 2-pyridones. This iron complex demonstrated antiinsectan and antifeedant properties similar to those previously found for leporin A. The OE::lepE strain showed reduced levels of conidia and sclerotia suggesting that unscheduled leporin production affects fungal developmental programs.
The β-lactams are the most widely used group of antibiotics in human health and agriculture, but this is under threat due to the persistent rise of pathogenic resistance. Several compounds, including ...tunicamycin (TUN), can enhance the antibacterial activity of the β-lactams to the extent of overcoming resistance, but the mammalian toxicity of TUN has precluded its use in this role. Selective hydrogenation of TUN produces modified compounds (TunR1 and TunR2), which retain the enhancement of β-lactams while having much lower mammalian toxicity. Here we show that TunR1 and TunR2 enhance the antibacterial activity of multiple β-lactam family members, including penems, cephems, and third-generation penicillins, to a similar extent as does the native TUN. Eleven of the β-lactams tested were enhanced from 2 to >256-fold against Bacillus subtilis, with comparable results against a penicillin G-resistant strain. The most significant enhancements were obtained with third-generation aminothiazolidyl cephems, including cefotaxime, ceftazidime, and cefquinome. These results support the potential of low toxicity tunicamycin analogs (TunR1 and TunR2) as clinically valid, synergistic enhancers for a broad group of β-lactam antibiotics.
•A VeA-dependent PKS in A. flavus produces a sclerotium-specific pigment.•The product of the PKS is the anthraquinone, asparasone.•The pigment has insect anti-feedant properties.•The pigment plays a ...role in sclerotial resistance to UV and heat stress.•A mechanism is proposed for synthesis of multiple metabolites by the PKS.
The filamentous fungus, Aspergillus flavus, produces the toxic and carcinogenic, polyketide synthase (PKS)-derived family of secondary metabolites termed aflatoxins. While analysis of the A. flavus genome has identified many other PKSs capable of producing secondary metabolites, to date, only a few other metabolites have been identified. In the process of studying how the developmental regulator, VeA, affects A. flavus secondary metabolism we discovered that mutation of veA caused a dramatic down-regulation of transcription of a polyketide synthase gene belonging to cluster 27 and the loss of the ability of the fungi to produce sclerotia. Inactivation of the cluster 27 pks (pks27) resulted in formation of greyish-yellow sclerotia rather than the dark brown sclerotia normally produced by A. flavus while conidial pigmentation was unaffected. One metabolite produced by Pks27 was identified by thin layer chromatography and mass spectral analysis as the known anthraquinone, asparasone A. Sclerotia produced by pks27 mutants were significantly less resistant to insect predation than were the sclerotia produced by the wild-type and more susceptible to the deleterious effects of ultraviolet light and heat. Normal sclerotia were previously thought to be resistant to damage because of a process of melanization similar to that known for pigmentation of conidia. Our results show that the dark brown pigments in sclerotia derive from anthraquinones produced by Pks27 rather than from the typical tetrahydronapthalene melanin production pathway. To our knowledge this is the first report on the genes involved in the biosynthesis of pigments important for sclerotial survival.
COP1 (constitutively photomorphogenic 1) is a RING-finger-containing protein that functions to repress plant photomorphogenesis, the light-mediated programme of plant development. Mutants of COP1 are ...constitutively photomorphogenic, and this has been attributed to their inability to negatively regulate the proteins LAF1 (ref. 1) and HY5 (ref. 2). The role of COP1 in mammalian cells is less well characterized. Here we identify the tumour-suppressor protein p53 as a COP1-interacting protein. COP1 increases p53 turnover by targeting it for degradation by the proteasome in a ubiquitin-dependent fashion, independently of MDM2 or Pirh2, which are known to interact with and negatively regulate p53. Moreover, COP1 serves as an E3 ubiquitin ligase for p53 in vitro and in vivo, and inhibits p53-dependent transcription and apoptosis. Depletion of COP1 by short interfering RNA (siRNA) stabilizes p53 and arrests cells in the G1 phase of the cell cycle. Furthermore, we identify COP1 as a p53-inducible gene, and show that the depletion of COP1 and MDM2 by siRNA cooperatively sensitizes U2-OS cells to ionizing-radiation-induced cell death. Overall, these results indicate that COP1 is a critical negative regulator of p53 and represents a new pathway for maintaining p53 at low levels in unstressed cells.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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