Insect Integument | ScienceGate

Carbon catabolite repression (CCR) is critical for the preferential utilization of glucose derived from environmental carbon sources and regulated by carbon catabolite repressor A (Cre1/CreA) in filamentous fungi. However, a role of Cre1-mediated CCR in insect-pathogenic fungal utilization of host nutrients during normal cuticle infection (NCI) and hemocoel colonization remains explored insufficiently. Here, we report an indispensability of Cre1 for Beauveria bassiana’s utilization of nutrients in insect integument and hemocoel. Deletion of cre1 resulted in severe defects in radial growth on various media, hypersensitivity to oxidative stress, abolished pathogenicity via NCI or intrahemocoel injection (cuticle-bypassing infection) but no change in conidial hydrophobicity and adherence to insect cuticle. Markedly reduced biomass accumulation in the Δcre1 cultures was directly causative of severe defect in aerial conidiation and reduced secretion of various cuticle-degrading enzymes. The majority (1117) of 1881 dysregulated genes identified from the Δcre1 versus wild-type cultures were significantly downregulated, leading to substantial repression of many enriched function terms and pathways, particularly those involved in carbon and nitrogen metabolisms, cuticle degradation, antioxidant response, cellular transport and homeostasis, and direct/indirect gene mediation. These findings offer a novel insight into profound effect of Cre1 on the insect-pathogenic lifestyle of B. bassiana.

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Tissue polarity in an insect segment: denticle patterns resemble spontaneously forming fibroblast patterns

Development ◽

10.1242/dev.100.1.171 ◽

1987 ◽

Vol 100 (1) ◽

pp. 171-177 ◽

Cited By ~ 1

Author(s):

K. Nubler-Jung

Keyword(s):

Cell Polarity ◽

Planar Cell Polarity ◽

Orthogonal Transformation ◽

Characteristic Pattern ◽

Additional Parameter ◽

Normal Pattern ◽

Cell Behaviour ◽

Tissue Polarity ◽

Insect Integument ◽

Parallel Arrays

The insect integument displays planar tissue polarity in the uniform posterior orientation of denticles and bristles. How do cell polarities become uniformly oriented in the plane of the epidermal sheet? We have already shown that it is possible to disturb uniform denticle orientation in abdominal segments of Dysdercus (Nubler- Jung, 1987). Here I report that abnormally oriented denticles tend to form small arrays with uniform orientation. Adjacent arrays with divergent orientations realize a small repertory of characteristic pattern elements. We obtain these pattern elements by orthogonal transformation of pattern elements that form spontaneously in confluent fibroblast cultures, which rely on autonomous cell behaviour, and which later simplify into patterns predicted by specific boundary conditions (Elsdale & Wasoff, 1976); the only additional parameter required is planar cell polarity. The abnormal patterns in Dysdercus may thus also form spontaneously and may also rely on autonomous cell behaviour. The normal pattern is predicted by the parallel segment boundaries. I propose that the characteristic pattern elements in the larval epidermis may arise because elongated epidermal cells tend to arrange in parallel arrays and to orient in the same direction. The normal posterior orientation of cell polarities may result from orienting cues provided by the anterior and by the posterior intersegmental regions.

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Neural regulation of pupariation in tsetse larvae.

Journal of Experimental Biology ◽

10.1242/jeb.173.1.11 ◽

1992 ◽

Vol 173 (1) ◽

pp. 11-24

Author(s):

J Zdárek ◽

D L Denlinger

Keyword(s):

Sagittal Plane ◽

Neural Mechanism ◽

The Body ◽

Nerve Transection ◽

Sarcophaga Bullata ◽

Point Separation ◽

Central Inhibition ◽

Tanning Process ◽

The Central Nervous System ◽

Insect Integument

A neural mechanism coordinates pupariation behavior and tanning in the tsetse larva. At parturition, the mature larva has already received sufficient ecdysteroid to commit the epidermal cells to metamorphosis but, before sclerotization and tanning of the cuticle can begin, the larva must first select a pupariation site and then proceed through a stereotypic sequence of pupariation behavior that culminates in the formation of a smooth, ovoid puparium. Both pupariation behavior and tanning are inhibited by the central nervous system (CNS) during the wandering phase. This central inhibition is maintained by sensory input originating in the extreme posterior region of the body. At the transition from wandering to pupariation, the posterior signal that induces inhibition of pupariation behavior is removed and the larva begins the contractions associated with pupariation, but the CNS inhibition of tanning persists. At this point, separation of the body into two halves by ligation or nerve transection prevents tanning of the anterior half (containing the CNS), whereas the denervated integument of the posterior half tans completely. Transection of nerves to the midline of the body produces larvae with a tanning pattern that ends abruptly along a sagittal plane, implying that the central control of this process is uncoupled between the left and right regions of the CNS. A few minutes later, when the final shape of the puparium is completed, the CNS inhibition is lifted and the tanning process begins. At this time, separation of the body into two halves by ligation or nerve transection has no inhibitory effects on either part. Exogenous ecdysteroids fail to release the CNS inhibition, and hemolymph containing the pupariation factors from Sarcophaga bullata have no accelerating effects on tsetse pupariation. These results imply that regulation of metamorphosis in the insect integument is not the exclusive domain of blood-borne hormones.

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Action of the Prothoracic Gland on the Insect Integument in Vitro

Applied Entomology and Zoology ◽

10.1303/aez.7.71 ◽

1972 ◽

Vol 7 (2) ◽

pp. 71-78 ◽

Cited By ~ 16

Author(s):

Noriaki AGUI ◽

Yasuo KIMURA ◽

Masatsugu FUKAYA

Keyword(s):

Prothoracic Gland ◽

Insect Integument

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Entomopathogenic fungi as biological controllers: New insights into their virulence and pathogenicity

Archives of Biological Sciences ◽

10.2298/abs1201021s ◽

2012 ◽

Vol 64 (1) ◽

pp. 21-42 ◽

Cited By ~ 48

Author(s):

Ali Shahid ◽

Qayyum Rao ◽

Allah Bakhsh ◽

Tayyab Husnain

Keyword(s):

Entomopathogenic Fungi ◽

Extracellular Enzymes ◽

Insect Pests ◽

Microbial Control ◽

Successful Infection ◽

Fungal Entomopathogens ◽

Penetration Ability ◽

Insect Integument ◽

Managed Ecosystems ◽

Effective Use

Entomopathogenic fungi vary considerably in their mode of action and virulence. Successful infection depends primarily on the adherence and penetration ability of a fungus to the host integuments. A variety of extracellular enzymes is produced during the degradation of insect integument. The attempts to control insects have changed over time from chemicals to natural control methods. This is why the development of natural methods of insect control or biopesticides, is preferred. By the use of fungal entomopathogens, insect pests can be controlled. There is no doubt that insects have been used for many years, but their effective use in the field remains elusive. However, their additional role in nature has also been discovered. Comparison of entomopathogens with conventional chemical pesticides depends on their efficiency and cost. In addition to efficiency, there are advantages in using microbial control agents, such as human safety and other non-target organisms; pesticide residues are minimized in food and biodiversity increased in managed ecosystems. In the present review the pathogenicity and virulence of entomopathogenic fungi and their role as biological control agents using biotechnology will be discussed.

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