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The glyoxylate cycle is required for temporal regulation of virulence by…
The glyoxylate cycle is required for temporal regulation of virulence by the plant pathogenic fungus Magnaporthe grisea
Experimental procedure
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Plant infection
plant infections were performed using 14-day-old seedlings of rice cultivar CO-39 or 10-day-old seedlings of barley cultivar Golden Promise that both are very susceptible to blast disease
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suspension was sprayed evenly onto rice plants and seedlings were incubated in a controlled environment chamber until disease symptoms appeared
disease lesion densities were recorded from 20 to 30 infected leaves using 5cm section of each leaf.
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Introduction
Magnaporthe grisea:cause rice blast disease -appressorium is the structure that induce the infection. -appressorium has the special characteristics which is: melanin-pigmented cells which develop turgor pressure to rupture the rice leaf cuticle.
- whole seedling will die,grain-bearing structure will destroyed.
the turgor pressure induce by the accumulation of glycerol in the cell. glycerol is highly soluble osmolyte which cause rapid influx ofwater into the appressorium to generate the pressure(hydrostatic pressure)
the biosynthesis of glycerol occurs rapidly during appressorium morphogenesis n involve mobilisation of the storage reverse from conidium.
lipid will move to appressorium take up by vacuole, at appressorium maturation.
glycerol is synthesize by triacylglycerol llipase activity abundantly in mature appressorium
-using lipid reverse mobilised from conidium
rapid lipolysis in M.grisea generate fatty acid and beta-oxidation of acetyl CoA. it require mecanism using acetyl CoAin development of the pathogen after infection.
ICL 1: isocitrate lyase express during apressorium development during appressorium maturation and invasive hyphae.
mutate ICL 1 delay the spore germination.
therefore, the glyoxylate cycle is important to fungal pathogens in both animal n plants.
Discussion
glyoxylate cycle assimilate 2 carbon compound into tricarboxylic acid cycle (TCA)and gluconeogenesis to generate glucose.
glyoxylate cycle using lipid metabolism as main source for ATP germination, invole beta-oxidation of fatty acid n production of acetyl CoA.
acetyl CoA ->glyoxylate cycle via isocitrate lyase
the production of malate by malase synthase.
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during conidial germination n appressorium formation: occurs in nutrient-free environment
lipid body mobilized from conidium to germ tube apex
during the presence of turgor genertion, lipid bodies taken up by vacuoles before lipolysis.
M.grisea use lipid metabolism during appressorium formation which conribute to ATP generation and melanin biosynthesis.
lipolysis important for turgor generation via synthesis of glycerol which accumulate in appresoria
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high-level express of ICL 1 during conidia germination n apressorium formation indicates glyoxylate cycle is stimulated.
ICL 1 express during penetration peg formation n invasive hyphae.
initial stage of infection:
-lipid metabolism ploriferate
-glucose acquisite from plant tissue
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