Effect of nutrition on growth and virulence of the entomopathogenic fungus<i>Beauveria bassiana</i>

Safavi, Seyed Ali; Shah, Farooq A.; Pakdel, A Kharazi; Rasoulian, Gh. R.; Bandani, Ali Reza; Butt, Tariq M.

doi:10.1111/j.1574-6968.2007.00666.x

Cited by 131 publications

(125 citation statements)

References 35 publications

Supporting

Mentioning

103

Contrasting

Unclassified

Order By: Relevance

“…Here we found that Bbhog1 was an important virulence determinant of B. bassiana and influenced at least three aspects of infection, spore viability, adherence to the insect cuticle, and appressorium formation. The rate of conidial germination is an important indicator of virulence in entomopathogenic fungi and is to some degree correlated with virulence (2,26,43,46). It was demonstrated previously that physical manipulation of growth conditions can significantly modify the endogenous compounds synthesized and channeled into the propagules of fungi (33,38).…”

Section: Discussionmentioning

confidence: 99%

Mitogen-Activated Protein Kinase hog1 in the Entomopathogenic FungusBeauveria bassianaRegulates Environmental Stress Responses and Virulence to Insects

Zhang

Zhao

Fang

et al. 2009

Appl Environ Microbiol

153

101

View full text Add to dashboard Cite

Beauveria bassiana is an economically important insect-pathogenic fungus which is widely used as a biocontrol agent to control a variety of insect pests. However, its insecticide efficacy in the field is often influenced by adverse environmental factors. Thus, understanding the genetic regulatory processes involved in the response to environmental stress would facilitate engineering and production of a more efficient biocontrol agent. Here, a mitogen-activated protein kinase (MAPK)-encoding gene, Bbhog1, was isolated from B. bassiana and shown to encode a functional homolog of yeast HIGH-OSMOLARITY GLYCEROL 1 (HOG1). A Bbhog1 null mutation was generated in B. bassiana by targeted gene replacement, and the resulting mutants were more sensitive to hyperosmotic stress, high temperature, and oxidative stress than the wild-type controls. These results demonstrate the conserved function of HOG1 MAPKs in the regulation of abiotic stress responses. Interestingly, ⌬Bbhog1 mutants exhibited greatly reduced pathogenicity, most likely due to a decrease in spore viability, a reduced ability to attach to insect cuticle, and a reduction in appressorium formation. The transcript levels of two hydrophobin-encoding genes, hyd1 and hyd2, were dramatically decreased in a ⌬Bbhog1 mutant, suggesting that Bbhog1 may regulate the expression of the gene associated with hydrophobicity or adherence.Mycoinsecticides are important insect pest control agents (10,19,41). Unlike entomopathogenic bacteria and viruses that invade insects through their digestive tracks, fungal pathogens penetrate the host integument and are considered the only group of microbial biocontrol agents active against sucking-type insect pests (21, 49). However, low killing speed and sensitivity to adverse environment factors such as desiccation, high temperature, and UV radiation limit the widespread use of entomopathogenic fungi (6,22,40). Thus, an understanding of the regulatory processes involved in response to environment stress is essential for commercial development and improvement of these biocontrol fungi.Mitogen-activated protein kinases (MAPKs), a family of serine-threonine protein kinases, are widespread in eukaryotic cells and play crucial roles in transduction of a variety of extracellular signals and regulation of various development and differentiation processes (37, 45). MAPKs are usually activated by MAPK kinases, which are in turn activated by MAPK kinase kinases. These MAPK kinase kinase-MAPK kinase-MAPK cascades are conserved in eukaryotic cells and have been studied extensively in many organisms (45). In Saccharomyces cerevisiae, at least five MAPK pathways have been identified. These pathways are designated the FUS3, KSS1, HOG1, SLT2, and SMK1 MAPK cascades, and they are involved in mating, filamentous growth, the high-osmolarity response, cell integrity, and ascospore formation, respectively (20). Recent studies showed that homologs of HOG1 are involved in responses to osmotic stress (12,29,44,58), oxidative stress (28, 47), heat shock (28), and ...

show abstract

Section: Discussionmentioning

confidence: 99%

Mitogen-Activated Protein Kinase hog1 in the Entomopathogenic FungusBeauveria bassianaRegulates Environmental Stress Responses and Virulence to Insects

Zhang

Zhao

Fang

et al. 2009

Appl Environ Microbiol

153

101

View full text Add to dashboard Cite

show abstract

“…Both LR2 and TA isolate has sparse sporulation on PDA compared to SDA and they differed significantly, while isolate MG cultured on both SDA and PDA had sparse sporulation. Some strains of M. anisopliae and Beauveria bassiana have been reported to produce high to maximum conidial yield on SDA media which had a C/N ratio equivalent of 35:1 [19,20] . Conversely, it had also been reported that several isolates of B. bassiana and M. anisopliae were able to produce maximum yield of conidia on PDA a low C/N ratio equivalent medium of 10:1 [19,20,22] .…”

Section: Discussionmentioning

confidence: 99%

“…Some strains of M. anisopliae and Beauveria bassiana have been reported to produce high to maximum conidial yield on SDA media which had a C/N ratio equivalent of 35:1 [19,20] . Conversely, it had also been reported that several isolates of B. bassiana and M. anisopliae were able to produce maximum yield of conidia on PDA a low C/N ratio equivalent medium of 10:1 [19,20,22] . Some isolates of entomopathogens like B. Bassiana, M. anisopliae and Paecilomyces fumosoroseus cultured in liquid medium with low C/N ratio of 10:1 also resulted in maximum sporulation [23] .…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Metarhizium anisopliae var. anisopliae (Deuteromycotina: Hyphomycete) Isolates and their Effects on Subterranean Termite Coptotermes curvignathus (Isoptera: Rhinotermitidae)

Hoe¹,

Bong²,

Kadir³

et al. 2009

American J. of Agricultural and Biological Sciences

View full text Add to dashboard Cite

Problem statement: Coptotermes curvignathus (Isoptera: Rhinotermitidae) is a common termite pest found in oil palm plantation planted on peat. Currently, the control methods focus on using insecticides that lead to high cost and adverse effect to the environment. Approach: Biological control like the use of entomopathogens provides an alternative control method for termite infestation problem. However, several factors need to be investigated in order to obtain a virulent strain with potential to be developed into a biopesticide. Results: Three local isolates (MG, LR2 and TA) of Metarhizium anisopliae were obtained and identified as M. anisopliae var. anisopliae using molecular techniques. Growth performance of isolates on four basal media namely, Potato Dextrose Agar (PDA), Potato Dextrose Agar with 1% yeast extract (PDAY), Sabaroud Dextrose Agar (SDA) and Sabaroud Dextrose Agar with 1% yeast extract (SDAY) was assessed. The pathogenicity of each isolate was tested against subterranean termite Coptotermes curvignathus at three concentrations of 1×10 6 , 1×10 7 and 1×10 8 conidia mL −1 . Infections of the isolates were examined using electron microscopy technique. The growth performance of each isolate differed significantly. Among all basal media, only SDAY was able to produce high growth performance and thick conidia mats with all isolates. The most pathogenic isolate was LR2, which caused 100% mortality at 1×10 7 conidia mL −1 within 3 days post-inoculation. Conclusion/Recommendations: All three isolates were pathogenic against C. curvignathus as they were able to germinate and penetrate into the termite cuticle within 15 hours post-inoculation. The three local isolates of M. anisopliae var. anisopliae have potential to be developed as biopesticides to control termites, C. curvignathus in oil palm plantations.

show abstract

“…When BbJEN1 was disrupted through the homologous recombination method, the same phenomenon was observed, whereas when the gene was overexpressed, the conidial yield was significantly decreased, suggesting that the conidial yield is relative to BbJEN1 expression. For fungi, the carbon source is considered an important nutrition factor for conidial yield (28,42,44). BbJEN1p can transfer carboxylates into cells.…”

Section: Discussionmentioning

confidence: 99%

Carboxylate Transporter Gene JEN1 from the Entomopathogenic Fungus Beauveria bassiana Is Involved in Conidiation and Virulence

Jin

Zhang

Fang

et al. 2010

Appl Environ Microbiol

View full text Add to dashboard Cite

Beauveria bassiana is an important entomopathogenic fungus widely used as a biological agent to control insect pests. A gene (B. bassiana JEN1 [BbJEN1]) homologous to JEN1 encoding a carboxylate transporter in Saccharomyces cerevisiae was identified in a B. bassiana transfer DNA (T-DNA) insertional mutant. Disruption of the gene decreased the carboxylate contents in hyphae, while increasing the conidial yield. However, overexpression of this transporter resulted in significant increases in carboxylates and decreased the conidial yield. BbJEN1 was strongly induced by insect cuticles and highly expressed in the hyphae penetrating insect cuticles not in hyphal bodies, suggesting that this gene is involved in the early stage of pathogenesis of B. bassiana. The bioassay results indicated that disruption of BbJEN1 significantly reduced the virulence of B. bassiana to aphids. Compared to the wild type, ⌬BbJEN1 alkalinized the insect cuticle to a reduced extent. The alkalinization of the cuticle is a physiological signal triggering the production of pathogenicity. Therefore, we identified a new factor influencing virulence, which is responsible for the alkalinization of the insect cuticle and the initiation of fungal pathogenesis in insects.Mycoinsecticides are considered promising biological control agents and alternatives or supplements to chemical pesticides (15). However, the dearth of physiological, genetic, and molecular knowledge of entomopathogenic fungi has retarded their widespread application.For mycoinsecticide improvement, greater attention and effort have been given to elucidate the mechanisms of fungal pathogenesis (13,14,18,20,29,49,50,51,52,53). Entomopathogenic fungi, e.g., Metarhizium anisopliae and Beauveria bassiana, invade their hosts by direct penetration of the host exoskeleton or cuticle. M. anisopliae and B. bassiana produce hydrophobic spores which contact and adhere to the insect cuticle (12). Once attached, the conidium germinates and the germ tubes differentiate into swollen infection structures called appressoria. The appressoria produce penetration pegs which penetrate the insect cuticle via cuticle-degrading enzymes (11,19,46) as well as mechanical pressure (24, 53). Hyphae proliferate within the hemocoel, emerge from inside the insect, and subsequently conidiate on the cadaver (15). However, much remains to be elucidated regarding the mechanisms of insect fungal pathogenesis.To obtain detailed knowledge of the mechanisms of fungal pathogenesis, a pool of B. bassiana transfer DNA (T-DNA) insertional mutants had been generated through an Agrobacterium-mediated-transformation method (21). A mutant, designated T12, characterized by the presence of more conidia, was isolated, and its flanking sequence was obtained by T-DNA tagging. The flanking fragment contained an open reading frame (ORF), which corresponded to a gene termed JEN1, encoding a transporter of carboxylates (http://www.ncbi.nlm .nih.gov/Blast.cgi). Organic acid transportation is important for the metabolism of almost all cells ...

show abstract

Effect of nutrition on growth and virulence of the entomopathogenic fungusBeauveria bassiana

Cited by 131 publications

References 35 publications

Mitogen-Activated Protein Kinase hog1 in the Entomopathogenic FungusBeauveria bassianaRegulates Environmental Stress Responses and Virulence to Insects

Mitogen-Activated Protein Kinase hog1 in the Entomopathogenic FungusBeauveria bassianaRegulates Environmental Stress Responses and Virulence to Insects

Evaluation of Metarhizium anisopliae var. anisopliae (Deuteromycotina: Hyphomycete) Isolates and their Effects on Subterranean Termite Coptotermes curvignathus (Isoptera: Rhinotermitidae)

Carboxylate Transporter Gene JEN1 from the Entomopathogenic Fungus Beauveria bassiana Is Involved in Conidiation and Virulence

Contact Info

Product

Resources

About