Inhibition of desert locust (Schistocerca gregaria) Malpighian tubule fluid secretion by destruxins, cyclic peptide toxins from the insect pathogenic fungus Metarhizium anisopliae

1993 ◽  
Vol 39 (9) ◽  
pp. 797-804 ◽  
Author(s):  
P.J. James ◽  
M.J. Kershaw ◽  
S.E. Reynolds ◽  
A.K. Charnley
Keyword(s):  
Metarhizium Anisopliae ◽  
Cyclic Peptide ◽  
Schistocerca Gregaria ◽  
Pathogenic Fungus ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Desert Locust ◽  
Peptide Toxins ◽  
Tubule Fluid

Anti-diuresis in the blood-feeding insect Rhodnius prolixus Stål: the peptide CAP2b and cyclic GMP inhibit Malpighian tubule fluid secretion.

1997 ◽  
Vol 200 (17) ◽  
pp. 2363-2367 ◽  
Author(s):  
M C Quinlan ◽  
N J Tublitz ◽  
M J O'Donnell
Keyword(s):  
Cyclic Gmp ◽  
Physiological Role ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Blood Feeding ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Tubule Fluid ◽  
Secretion Rates

Rhodnius prolixus eliminates NaCl-rich urine at high rates following its infrequent but massive blood meals. This diuresis involves stimulation of Malpighian tubule fluid secretion by diuretic hormones released in response to distention of the abdomen during feeding. The precipitous decline in urine flow that occurs several hours after feeding has been thought until now to result from a decline in diuretic hormone release. We suggest here that insect cardioacceleratory peptide 2b (CAP2b) and cyclic GMP are part of a novel mechanism of anti-diuresis. Secretion rates of 5-hydroxytryptamine-stimulated Malpighian tubules are reduced by low doses of CAP2b or cyclic GMP. Maximal secretion rates are restored by exposing tubules to 1 mmol l-1 cyclic AMP. Levels of cyclic GMP in isolated tubules increase in response to CAP2b, consistent with a role for cyclic GMP as an intracellular second messenger. Levels of cyclic GMP in tubules also increase as urine output rates decline in vivo, suggesting a physiological role for this nucleotide in the termination of diuresis.

scholarly journals Agrobacterium-Mediated Disruption of a Nonribosomal Peptide Synthetase Gene in the Invertebrate Pathogen Metarhizium anisopliae Reveals a Peptide Spore Factor

2008 ◽  
Vol 74 (14) ◽  
pp. 4366-4380 ◽  
Author(s):  
Yong-Sun Moon ◽  
Bruno G. G. Donzelli ◽  
Stuart B. Krasnoff ◽  
Heather McLane ◽  
Mike H. Griggs ◽  
...  
Keyword(s):  
Metarhizium Anisopliae ◽  
Developmental Stages ◽  
Cyclic Peptide ◽  
Pathogenic Fungus ◽  
Nonribosomal Peptide Synthetase ◽  
Dna Polymorphisms ◽  
Beet Armyworm ◽  
Nonribosomal Peptide ◽  
Peptide Synthetase

ABSTRACT Numerous secondary metabolites have been isolated from the insect pathogenic fungus Metarhizium anisopliae, but the roles of these compounds as virulence factors in disease development are poorly understood. We targeted for disruption by Agrobacterium tumefaciens-mediated transformation a putative nonribosomal peptide synthetase (NPS) gene, MaNPS1. Four of six gene disruption mutants identified were examined further. Chemical analyses showed the presence of serinocyclins, cyclic heptapeptides, in the extracts of conidia of control strains, whereas the compounds were undetectable in ΔManps1 mutants treated identically or in other developmental stages, suggesting that MaNPS1 encodes a serinocyclin synthetase. Production of the cyclic depsipeptide destruxins, M. anisopliae metabolites also predicted to be synthesized by an NPS, was similar in ΔManps1 mutant and control strains, indicating that MaNPS1 does not contribute to destruxin biosynthesis. Surprisingly, a MaNPS1 fragment detected DNA polymorphisms that correlated with relative destruxin levels produced in vitro, and MaNPS1 was expressed concurrently with in vitro destruxin production. ΔManps1 mutants exhibited in vitro development and responses to external stresses comparable to control strains. No detectable differences in pathogenicity of the ΔManps1 mutants were observed in bioassays against beet armyworm and Colorado potato beetle in comparison to control strains. This is the first report of targeted disruption of a secondary metabolite gene in M. anisopliae, which revealed a novel cyclic peptide spore factor.

Acid-Base Variables in Malpighian Tubule Secretion and Response to Acidosis

1991 ◽  
Vol 159 (1) ◽  
pp. 433-447 ◽  
Author(s):  
ANDREW P. STAGG ◽  
JON F. HARRISON ◽  
JOHN E. PHILLIPS
Keyword(s):  
Schistocerca Gregaria ◽  
Malpighian Tubule ◽  
Malpighian Tubules ◽  
Acid Base ◽  
Acid Injection ◽  
Before And After ◽  
Acid Load ◽  
Acid Base Status ◽  
Tubule Fluid

1. Malpighian tubule fluid from Schistocerca gregaria adults, starved for 1 day, was collected in situ by cannulation of the gut, both before and after injecting 10 μmol of HCl or NaCl into the haemocoel. 2. Haemolymph pH at the neck remained depressed by 0.3 units for at least 6 h in HCl- as compared to NaCl-injected locusts. A lower haemolymph pH persisted near the acid injection site for several hours. 3. The pH of tubule fluid remained about 0.5 units more acid than haemolymph under all conditions. Thus, net tubular acid secretion was proportional to haemolymph acid-base status. 4. The greater acidity of tubular fluid after acid injection was associated with lower estimated bicarbonate concentrations and higher Pcoco2 without any change in total CO2 when compared to controls. 5. The combined contribution of bicarbonate, phosphate and urate to total buffering capacity of tubular fluid was estimated to be 75°, with bicarbonate responsible for 55° of the total. 6. The maximum rate of acid removal by all Malpighian tubules of starved locusts, including H+ trapped in ammonium ions, was calculated to be very small in relation to the acid load injected into the haemocoel Note: To whom reprint requests should be directed.

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