Endogenous Substrates of Dormant, Activated and Germinating Ascospores of Neurospora Tetrasperma.

Lingappa, B. T.; Sussman, Alfred S.

doi:10.1104/pp.34.4.466

Cited by 52 publications

(48 citation statements)

References 16 publications

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“…Interestingly, all segregants with a tpsA∆ allele were thermosenitive for growth while the CEA150 In A. nidulans, trehalose is known to accumulate during conidiogenesis (d 'Enfert & Fontaine, 1997) as well as in response to heat shock (Noventa-Jordao et al, 1999). In other fungal species, trehalose has been shown to accumulate in the stationary phase of growth and in response to an oxidative or osmotic shock (Hounsa et al, 1998 ;Lewis et al, 1995 ;Lingappa & Sussman, 1959 ;Van Laere, 1989 ;Wiemken, 1990). Accumulation of trehalose was therefore monitored in wild-type and tpsA∆ conidia as well as in germinating conidia that were subjected to a heat shock or an oxidative shock.…”

Section: Disruption Of the Tpsa Gene In A Nidulansmentioning

confidence: 99%

Trehalose is required for the acquisition of tolerance to a variety of stresses in the filamentous fungus Aspergillus nidulans The GenBank accession number for the sequence reported in this paper is AF043230.

et al. 2001

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Trehalose is a non-reducing disaccharide found at high concentrations in Aspergillus nidulans conidia and rapidly degraded upon induction of conidial germination. Furthermore, trehalose is accumulated in response to a heat shock or to an oxidative shock. The authors have characterized the A. nidulans tpsA gene encoding trehalose-6-phosphate synthase, which catalyses the first step in trehalose biosynthesis. Expression of tpsA in a Saccharomyces cerevisiae tps1 mutant revealed that the tpsA gene product is a functional equivalent of the yeast Tps1 trehalose-6-phosphate synthase. The A. nidulans tpsA-null mutant does not produce trehalose during conidiation or in response to various stress conditions. While germlings of the tpsA mutant show an increased sensitivity to moderate stress conditions (growth at 45 SC or in the presence of 2 mM H 2 O 2 ), they display a response to severe stress (60 min at 50 SC or in the presence of 100 mM H 2 O 2 ) similar to that of wild-type germlings. Furthermore, conidia of the tpsA mutant show a rapid loss of viability upon storage. These results are consistent with a role of trehalose in the acquisition of stress tolerance. Inactivation of the tpsA gene also results in increased steady-state levels of sugar phosphates but does not prevent growth on rapidly metabolizable carbon sources (glucose, fructose) as seen in Saccharomyces cerevisiae. This suggests that trehalose 6-phosphate is a physiological inhibitor of hexokinase but that this control is not essential for proper glycolytic flux in A. nidulans. Interestingly, tpsA transcription is not induced in response to heat shock or during conidiation, indicating that trehalose accumulation is probably due to a post-translational activation process of the trehalose 6-phosphate synthase.

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Section: Disruption Of the Tpsa Gene In A Nidulansmentioning

confidence: 99%

Trehalose is required for the acquisition of tolerance to a variety of stresses in the filamentous fungus Aspergillus nidulans The GenBank accession number for the sequence reported in this paper is AF043230.

et al. 2001

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“…Fatty acids in concentrations of 10-3 M and greater have been shown to inhibit pyruvate oxidation by rat kidney mitochondria (27). This is interesting in view of the fact that lipid appears to be the endogenous substrate for respiration during certain phases of the life cvcle of Neurospora (20).…”

Section: Discussionmentioning

confidence: 85%

“…They concluded that activation induices the formation of an oxidative system, possibly operating through the TCA cycle, that is different from that in the dormant ascospores. Recent work from this laboratory (20,38) on the nature of the endogenous substrates in dormant and activated ascospores supports this idea of a qualitative change in metabolism after activation.…”

mentioning

confidence: 65%

Studies on Pyruvate Metabolism and Cytochrome System in Neurospora Tetrasperma

Holton

1960

Plant Physiol.

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Although it has been known for more than 30 years that dornmancy in Neurospora ascospores can be broken by heat treatment (30), the mechanism is not yet understood. Goddard (10) concluded from his studies that the metabolic block overcome by the heat treatment was concerned with the enzyme carboxylase. Studies of Sussman et al (36) demonstrated that both the apoenzyme and coenzyme were present in dormant and heat-activated ascospores in nearly equivalent amounts. They concluded that activation induices the formation of an oxidative system, possibly operating through the TCA cycle, that is different from that in the dormant ascospores. Recent work from this laboratory (20, 38) on the nature of the endogenous substrates in dormant and activated ascospores supports this idea of a qualitative change in metabolism after activation.Because pyruvate appeared to be a key intermediate in the suggested development of an oxidative system, it was thought that pyruvic oxidase might be present in the activated ascospores but not in the dormant ascospores. Since anions of the size of pyruvate do not penetrate dormant spores (37), it is necessary to study pyruvate oxidation in cell-free extracts. The studies reported here were originally undertaken in an attempt to demonstrate the presence of this enzyme system in cell-free extracts of the ascospores and in other stages of the life cycle including conidia and mycelia of Neurospora tetraspern.a. A preliminary report of this work has been published (16). MATERIALS AND METHODSAscospores of Neurospora tetraspermna Shear and Dodge were produced from a cross of strains 394.4 and 394.5 originally obtained by Dr. A. S. Sussman from Dr. B. 0. Dodge. The ascospores were grown and harvested using the procedure of Goddard (9) by placing a suspension of ascospores in a centrifuge tube in a 580 C water bath for 10 minutes.Good nmycelial growth in liquid shake culture was obtained by inoculation of a suspension of conidia of strain 394.5 into the complete medium of Horowitz [cited by Ryan (26)]. Sixty-five ml of the medium were added to 250 ml Erlenmeyer flasks, inoculated with 5 ml of a conidial suspension and incubated on a reciprocal shaker at 21°C. The mycelium was harvested by filtration on a suction funnel and the mycelial mat obtained was washed with distilled water and used for enzyme preparations. In determining dry weights for the growth curve of the mycelium, the flask contents were washed into a tared, 25 ml, coarse porosity, fritted glass Buchner funnel, washed, and the mat and funnel dried to constant weight at 1050 C.Conidia were produced on 50 ml of Horowitz's medium solidified with 1.5 % agar in wide-mouth 500 ml Erlenmeyer flasks. After inoculation of the media with a suspension of strain 394.5 conidia, the fungus was allowed to grow for 2 days at 210 C under approximately 500 foot-candles of light. Conidia formation was stimulated by removal of the cotton plugs overnight (23). The conidia were harvested with distilled water and passed through glass wool in a Gooch crucible...

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“…Peptone required was as much as 30 to 50 times the weight of conidia to bring about germination ( Table 1). The ascospores of Neurospora tetrasperma utilize only endogenous reserves during germination (Lingappa & Sussman, 1959) and the amount utilized was less than 10 yo of the spore weight and this gives an idea as to the amounts of substrates that may be required for germination of 74 B. T. LINGAPPA AND Y. LINGAPPA spores. It is inconceivable that peptone might be required in such large quantities as a nutrient source to effect germination of conidia.…”

Section: Discussionmentioning

confidence: 99%

Effects of Nutrients on Self-Inhibition of Germination of Conidia of Glomerella cingulata

Lingappa¹,

Lingappa²

1965

Journal of General Microbiology

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SUMMARYThe percentage germination of suspensions of washed conidia of Glomerella cingzclata decreased with increasing concentrations of the conidia in distilled water. With 30 conidia/mm.2 greater than 90 yo germination was obtained, whereas the conidia from the same batch gave less than 3 yo germination when there were 3000 conidia/mm.2. This inhibition of germination of crowded conidia was nullified by adequate amounts of peptone; but aeration by shaking had no influence, so that oxygen lack was ruled out as a factor in the inhibition. Various adsorbents, ion exchange resins, vitamins and germination stimulating chemicals were ineffective in inducing germination of crowded conidia. Czapek-Dox mineral solution, Hoagland's mineral solution and Czapek-Dox glucose solution gave respectively 10, 30 and 40% germination of crowded conidia. The germination of conidia was improved by repeated washing with distilled water. Addition of various mineral salts and trace elements (Mg, Fe, Mn, Bo, Zn, Mo, Cu) were relatively ineffective or toxic. Glucose, or mannitol did not induce germination. Peptone and phenylalanine were most effective in promoting the germination of crowded conidia, but only in massive doses. Bimodal response of germination of conidia to added nutrients was noticed. Since the conidia germinated, when present at low concentrations in redistilled water without added nutrients, the conidia could not be considered as nutritionally deficient. The beneficial effect of nutrients in promoting the germination of crowded conidia may be due to inactivation of inhibitory metabolites from the conidia.

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Endogenous Substrates of Dormant, Activated and Germinating Ascospores of Neurospora Tetrasperma.

Cited by 52 publications

References 16 publications

Trehalose is required for the acquisition of tolerance to a variety of stresses in the filamentous fungus Aspergillus nidulans The GenBank accession number for the sequence reported in this paper is AF043230.

Trehalose is required for the acquisition of tolerance to a variety of stresses in the filamentous fungus Aspergillus nidulans The GenBank accession number for the sequence reported in this paper is AF043230.

Studies on Pyruvate Metabolism and Cytochrome System in Neurospora Tetrasperma

Effects of Nutrients on Self-Inhibition of Germination of Conidia of Glomerella cingulata

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