Biosynthetic Pathways of Glycerol Accumulation under Salt Stress in Aspergillus nidulans

Redkar, Rajendra J.; Locy, Robert D.; Singh, Narendra K.

doi:10.1006/emyc.1995.1030

Cited by 39 publications

(38 citation statements)

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“…We found GPD activity in M. grisea mycelium, but it was not induced by hyperosmotic stress. Instead, the activities of NADPHdependent dihydroxyacetone reductase and glyceraldehyde reductase were increased, suggesting that glycerol production during hyperosmotic stress in M. grisea may be more similar mechanistically to the process in A. nidulans than that in yeast (Redkar et al, 1995). This is consistent with our previous findings that hyperosmotic stress in M. grisea leads predominantly to arabitol generation, which is regulated by the OSM1 MAPK, and OSM1-independent production of smaller amounts of glycerol (Dixon et al, 1999).…”

Section: Discussionsupporting

confidence: 91%

“…Glycerol can also be produced from dihydroxyacetone by an NADPHdependent dihydroxyacetone reductase and from glyceraldehyde by an NADPH-dependent glyceraldehyde reductase (EC 1.1.1.77). In the filamentous fungus Aspergillus nidulans , both reactions are catalyzed by a single enzyme, an NADPH-dependent glycerol dehydrogenase (GD) (Redkar et al, 1995); this enzyme may also exist in budding yeast (Norbeck and Blomberg, 1997).…”

Section: Glycerol Biosynthesis In the Appressorium Of M Griseamentioning

confidence: 99%

“…Glycogen degradation during germination and subsequent deposition in differentiating germ tubes therefore do not occur in the absence of the PMK1 -encoded MAPK. (Redkar et al, 1995). CM, complete medium; DHA, dihydroxyacetone; DHAP, dihydroxyacetone phosphate; GAD, glyceraldehyde.…”

Section: Glycogen Degradation Occurs Before Appressorium Turgor Genermentioning

confidence: 99%

“…Glycerol-3-phosphate dehydrogenase (GPD) was assayed at room temperature by an adaptation of the method of Redkar et al (1995). Briefly, the 1-mL reaction reagent contained 20 mM imidazole-HCl, pH 7.0, 1 mM DTT, 1 mM MgCl 2 , 0.67 mM dihydroxyacetone phosphate, and either 0.09 or 0.2 mM NADH.…”

Section: Enzyme Assaysmentioning

confidence: 99%

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MAP Kinase and Protein Kinase A–Dependent Mobilization of Triacylglycerol and Glycogen during Appressorium Turgor Generation by Magnaporthe grisea

2000

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Magnaporthe grisea produces an infection structure called an appressorium, which is used to breach the plant cuticle by mechanical force. Appressoria generate hydrostatic turgor by accumulating molar concentrations of glycerol. To investigate the genetic control and biochemical mechanism for turgor generation, we assayed glycerol biosynthetic enzymes during appressorium development, and the movement of storage reserves was monitored in developmental mutants. Enzymatic activities for glycerol generation from carbohydrate sources were present in appressoria but did not increase during development. In contrast, triacylglycerol lipase activity increased during appressorium maturation. Rapid glycogen degradation occurred during conidial germination, followed by accumulation in incipient appressoria and dissolution before turgor generation. Lipid droplets also moved to the incipient appressorium and coalesced into a central vacuole before degrading at the onset of turgor generation. Glycogen and lipid mobilization did not occur in a ⌬ pmk1 mutant, which lacked the mitogen-activated protein kinase (MAPK) required for appressorium differentiation, and was retarded markedly in a ⌬ cpkA mutant, which lacks the catalytic subunit of cAMP-dependent protein kinase A (PKA). Glycogen and lipid degradation were very rapid in a ⌬ mac1 sum1-99 mutant, which carries a mutation in the regulatory subunit of PKA, occurring before appressorium morphogenesis was complete. Mass transfer of storage carbohydrate and lipid reserves to the appressorium therefore occurs under control of the PMK1 MAPK pathway. Turgor generation then proceeds by compartmentalization and rapid degradation of lipid and glycogen reserves under control of the CPKA/SUM1 -encoded PKA holoenzyme.

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Section: Discussionsupporting

confidence: 91%

Section: Glycerol Biosynthesis In the Appressorium Of M Griseamentioning

confidence: 99%

Section: Glycogen Degradation Occurs Before Appressorium Turgor Genermentioning

confidence: 99%

Section: Enzyme Assaysmentioning

confidence: 99%

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MAP Kinase and Protein Kinase A–Dependent Mobilization of Triacylglycerol and Glycogen during Appressorium Turgor Generation by Magnaporthe grisea

2000

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“…In true fungi, polyols, such as mannitol, arabitol, and glycerol, accumulate and exhibit multiple cellular functions. These include maintaining osmotic balance (40), generating turgor in appressoria (47), and quenching reactive oxygen generated within stressed fungal tissue or by plants during defense reactions (6,22). Sugar alcohols may form in plant-pathogenic fungi when their ␤-fructosidases transform plant sucrose to fructose, which is converted to sorbitol by sorbitol dehydrogenase; biosynthesis rather than direct uptake is more likely for colonizers of the majority of plants, including potato and tomato, which produce little of these compounds (45).…”

Section: Discussionmentioning

confidence: 99%

Sporangium-Specific Gene Expression in theOomycete Phytopathogen Phytophthorainfestans

Kim

Judelson

2003

Eukaryot Cell

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The oomycete genus Phytophthora includes many of the world's most destructive plant pathogens, which are generally disseminated by asexual sporangia. To identify factors relevant to the biology of these propagules, genes induced in sporangia of the potato late blight pathogen Phytophthora infestans were isolated using cDNA macroarrays. Of ϳ1,900 genes known to be expressed in sporangia, 61 were up-regulated >5-fold in sporangia versus hyphae based on the arrays, including 17 that were induced >100-fold. A subset were also activated by starvation and in a nonsporulating mutant. mRNAs of some genes declined in abundance after germination, while others persisted through the germinated zoospore cyst stage. Functions were predicted for about three-quarters of the genes, including potential regulators (protein kinases and phosphatases, transcription factors, and G-protein subunits), transporters, and metabolic enzymes. Predominant among the last were several dehydrogenases, especially a highly expressed sorbitol dehydrogenase that accounted for 3% of the mRNA. Sorbitol dehydrogenase activity also rose during sporulation and several stress treatments, paralleling the expression of the gene. Another interesting metabolic enzyme resembled creatine kinases, which previously were reported only in animals and trypanosomes. These results provide insight into the transcriptional and cellular processes occurring in sporangia and identify potential targets for crop protection strategies.Sporulation is central to the life cycles of most plant-pathogenic lower eukaryotes, including true fungi and oomycetes. The latter group encompasses important pathogens, such as Phytophthora, Pythium, and the downy mildews, which infect many economically significant hosts (14). The molecular biology of sporulation has been characterized in detail for several true fungi (1,11,28,43). However, little information exists on oomycetes, which despite their "fungus-like" appearance are more closely related to organisms such as diatoms and brown algae (3).Asexual sporangia play the major role in spreading Phytophthora infestans, which causes late blight of potato and tomato (17). The roles of nutrients, pH, aeration, light, and humidity in sporulation are well described (33,41). In older portions of plant lesions and in laboratory cultures, sporangia form upon aerial sporangiophores branched from hyphae. In some members of the genus, such as P. infestans, this occurs spontaneously as cultures age, but in others significant sporulation requires washing nutrients from media (41). In both cases, nuclear divisions rapidly occur within sporangiophores, and then nuclei and cytoplasm quickly flow into terminal swellings, which develop into sporangia (7, 32). These mature by forming a basal plug, which delimits the multinucleate sporangium from the coenocytic hypha, and an apical papilla, which is a future site of germination. Two modes of germination are possible in most oomycetes, including P. infestans. Indirect germination by way of zoospores predominates ...

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Biotechnology of Glycerol Production and Conversion in Yeasts

Semkiv

Dmytruk

Abbas

et al. 2017

Biotechnology of Yeasts and Filamentous Fungi

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Biosynthetic Pathways of Glycerol Accumulation under Salt Stress in Aspergillus nidulans

Cited by 39 publications

References 0 publications

MAP Kinase and Protein Kinase A–Dependent Mobilization of Triacylglycerol and Glycogen during Appressorium Turgor Generation by Magnaporthe grisea

MAP Kinase and Protein Kinase A–Dependent Mobilization of Triacylglycerol and Glycogen during Appressorium Turgor Generation by Magnaporthe grisea

Sporangium-Specific Gene Expression in theOomycete Phytopathogen Phytophthorainfestans

Biotechnology of Glycerol Production and Conversion in Yeasts

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