Insect Immune Response and Secondary Metabolites Quiz

The fat body is the main production site for antimicrobial peptides (AMPs) in insects.

Several types of AMPs have been identified, including defensins, cecoprins, diptericins, apidaecins, and hymenoptaecins.

Defensins have a broad spectrum of action against Gram-positive and some Gram-negative bacteria, fungi, and protists.

Recognition of intruders is initiated by pattern recognition receptors (PRRs) and β-glucan-binding proteins, which detect pathogen-associated molecular patterns (PAMPs) like lipolysaccharides (LPS), peptidoglycans (PGN), and β-1.3 glycans.

The humoral immune response to fungal infections is mediated by the Toll pathway.

TLR recognition of fungal microorganisms triggers a cascade reaction, leading to translocation of transcription factors and production of AMPs.

Toll pathway receptors can recognize PGNs with L-lysine residues.

JNK and JAK/STAT pathways are also involved in synthesizing antibacterial AMPs and stress/injury response proteins during fungal infections.

Other immune-related molecules produced by insects include lysozyme, Alternative protein sources, apolipophorin III, hemocyanin, and transferrin.

Transferrin expression is increased during B. bassiana and M. anisopliae infections.

Social insects exhibit grooming behavior, which helps prevent fungal colonization and may release fungistatic chitinase secretions.

Entomopathogenic fungi have evolved strategies to evade or overcome host defense systems, such as morphological changes and immune suppression.

Hypocreales fungi form thin-walled hyphal bodies to speed up dispersion and avoid detection.

More virulent fungal strains can reduce the number of granulocytes.

Entomopathogenic fungi in the Entomophthoromycota phylum take the form of protoplasts to evade detection and mask immunogenic carbohydrates.

Entomopathogenic fungi secrete secondary metabolites to cause paralysis and suppress immune responses.

Entomopathogenic fungi can be isolated using selective media, insect bait methods, or by harvesting from insect corpses.

Sample preparation is crucial for isolation, involving washes with surfactants and disinfection with sterilizing agents.

Environmental conditions such as high humidity and temperature are necessary for fungal growth.

Fungal growth can be inhibited by antibacterial agents and selective media additives like dodine, cyclohexamide, or benomyl.

Incubation should occur in darkness at ambient temperature for 5-7 days.

B. bassiana can be cultured on various media, including SMAY, PDA, and PDB.

M. anisopliae requires specific media for optimal growth.

The text discusses the common ways of assigning fungi to groups, focusing on entomopathogenic fungi and their characteristics.

Entomopathogenic fungi are mainly found in Ascomycota and Entomophthoromycota phyla.

Hypocreales order in Ascomycota contains important entomopathogenic fungi, such as Beauveria, Isaria, Hirsutella, Metarhizium, and Cordyceps.

Entomopathogenic fungi are parasitic organisms, which can infect insects and other arthropods like mites and ticks.

They have a heterotrophic metabolism, which makes them dependent on a host organism.

Entomopathogenic fungi can control natural insect populations by limiting their spread.

Infection begins when the spores adhere to the host's cuticle, followed by germination, penetration, and growth within the cuticle interstices.

Entomopathogenic fungi produce various cuticle-degrading enzymes, such as proteases, endoproteases, esterases, lipases, and chitinases, and organic acids.

The appressorium is a specialized structure that aids in concentrating physical and chemical energy on a small area of the cuticle for a successful attachment.

Once the immune response system is avoided, the fungus causes a depletion of nutrients and destruction of tissues, leading to insect death through factors like mechanical damage, nutrient depletion, and toxicosis.

Neuromuscular toxins such as beauvericin, beauverolide, bassianolide, and isarolide are produced by entomopathogenic fungi, causing symptoms like paralysis, slowness, and reduced responsiveness to external stimuli.

Entomopathogenic fungi have low to no residual toxicity and are developed as microbial insecticides for controlling pest arthropods in agriculture, forestry, and urban environments.