Nitrate Assimilation in the Basidiomycete Yeast Sporobolomyces roseus

Ali, A. H.; Hipkin, C. R.

doi:10.1099/00221287-131-8-1867

Cited by 11 publications

(12 citation statements)

References 14 publications

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“…cylindrosporum [23]. Interestingly, the occurrence of a similar mode of regulation has been inferred previously from physiological data obtained in nitrophilic yeasts such as Sporobolomyces roseus, Candida nitratophila and Rhodotorula glutinis [40,41] and in the mycorrhizal basidiomycete Rhizopogon roseolus [11]. The above fungi colonize different environments and are not closely related evolutionarily to each other, nor to T. borchii.…”

Section: Mode Of Regulation Of Tbnrt2supporting

confidence: 67%

Functional properties and differential mode of regulation of the nitrate transporter from a plant symbiotic ascomycete

Montanini

Viscomi

Bolchi

et al. 2006

Biochemical Journal

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Nitrogen assimilation by plant symbiotic fungi plays a central role in the mutualistic interaction established by these organisms, as well as in nitrogen flux in a variety of soils. In the present study, we report on the functional properties, structural organization and distinctive mode of regulation of TbNrt2 (Tuber borchii NRT2 family transporter), the nitrate transporter of the mycorrhizal ascomycete T. borchii. As revealed by experiments conducted in a nitrate-uptake-defective mutant of the yeast Hansenula polymorpha, TbNrt2 is a high-affinity transporter (K m = 4.7 µM nitrate) that is bispecific for nitrate and nitrite. It is expressed in free-living mycelia and in mycorrhizae, where it preferentially accumulates in the plasma membrane of root-contacting hyphae. The TbNrt2 mRNA, which is transcribed from a single-copy gene clustered with the nitrate reductase gene in the T. borchii genome, was specifically up-regulated following transfer of mycelia to nitrate-(or nitrite)-containing medium. However, at variance with the strict nitrate-dependent induction commonly observed in other organisms, TbNrt2 was also up-regulated (at both the mRNA and the protein level) following transfer to a nitrogen-free medium. This unusual mode of regulation differs from that of the adjacent nitrate reductase gene, which was expressed at basal levels under nitrogen deprivation conditions and required nitrate for induction. The functional and expression properties, described in the present study, delineate TbNrt2 as a versatile transporter that may be especially suited to cope with the fluctuating (and often low) mineral nitrogen concentrations found in most natural, especially forest, soils.

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Section: Mode Of Regulation Of Tbnrt2supporting

confidence: 67%

Functional properties and differential mode of regulation of the nitrate transporter from a plant symbiotic ascomycete

Montanini

Viscomi

Bolchi

et al. 2006

Biochemical Journal

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“…polyrnorpha. H. anomala showed N R activity only in the presence of nitrate, in contrast to Sporobolomyces roseus (Ali & Hipkin, 1985) and Candida nitratophilu Cannons et al, 1986) where NR was present in nitrogen-free medium. The levels of NR protein present under different conditons (Figs 2, 3 and 5) and the observed effect of cycloheximide on NR activity (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast with the situation for filamentous fungi (Pateman & Kinghorn, 1976;DunnColeman et al, 1984;Wray & Kinghorn, 1989), the regulation of NR by nitrogen and carbon sources has been little studied in yeast. So far (Ali & Hipkin, 1985Cannons et al, 1986;Jones et al, 1987;Hipkin, 1989) it has been shown that NR appears in cells cultured in nitrate-containing media and is absent in ammoniumcultured cells.…”

Section: Introductionmentioning

confidence: 99%

Effect of nitrogen source on the levels of nitrate reductase in the yeast Hansenula anomala

González

Siverio²

1992

Journal of General Microbiology

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Levels of nitrate reductase (NR) protein inHansenula anomafa and Hansenula wingei were determined using specific antiserum raised against the enzyme from H. anomafa. Extracts from nitrate-grown cells contained NR protein, while in those from cells grown on ammonium, glutamine or peptone, no cross-reacting material could be observed. Enzyme activity correlated with the levels of cross-reacting material. When nitrate was used as nitrogen source, NR was always present, even in cultures with ammonium, glutamine or peptone, although in these cases both the levels of activity and protein were lower. NR activity was consistently two to four times higher in cells grown in glucose than in cells grown in ethanol. Nitrate was required for NR induction, and deprivation of nitrate from nitrate-grown cells resulted in a rapid loss of NR activity.

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“…These indications suggest that in this respect H . polymorpha NCYC 495 is similar to Aspergillus nidulans (Cove, 1979), Neurospora crassa (Garrett & Amy, 1978), Hansenula wingei ATCC 28162 (Jones et al, 1987), Sporobolomyces roseus (Ali & Hipkin, 1985) and H . polymorpha CBS 4732 (Gonzalez & Siverio, 1992) but differs from H .…”

Section: Discussionmentioning

confidence: 99%

“…polymorpha differs from S . roseus and C. nitratophila in that removal of ammonium from ammonium-grown cultures does not bring about ' gratuitous ' NR activities (Ali & Hipkin, 1985;Cannons et al, 1986). Thus in this yeast, NR activity does not seem to be strongly regulated by derepression.…”

Section: Discussionmentioning

confidence: 99%

Nitrate reduction and the isolation of Nit− mutants in Hansenula polymorpha

1998

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Hansenula polymorpha (syn. Pichia angusta) is able to grow on nitrate as sole nitrogen source. Nitrate reductase (NR) assays, optimized in crude extracts from nitrate-grown cells, revealed that NR preferentially used NADPH, but also used NADH, as electron donor and required FAD for maximum activity. NR activity was present in nitrate-grown and nitrite-grown cells, and was absent in cells grown in ammonium, glutamate and methylamine. Addition of reduced nitrogen compounds t o nitrate-grown cells led to loss of NR activity, even if added with nitrate. Under nitrogen starvation, NR activity was not observed; however, following growth on nitrate, NR activity is maintained in the absence of nitrate. Increases but not decreases in NR activity were dependent on protein synthesis. Conditions for chlorate selection were optimized, and Nit' (nitrate') mutants were isolated. Some of these mutants showed reduced or absent NR activity. Sixtyone NR' mutants revealed the monogenic recessive nature of their lesions and were grouped in 10 complementation classes. These mutants will be used in gene cloning experiments aimed at identifying structural and regulatory elements involved in the first step of nitrate reduction.

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Nitrate Assimilation in the Basidiomycete Yeast Sporobolomyces roseus

Cited by 11 publications

References 14 publications

Functional properties and differential mode of regulation of the nitrate transporter from a plant symbiotic ascomycete

Functional properties and differential mode of regulation of the nitrate transporter from a plant symbiotic ascomycete

Effect of nitrogen source on the levels of nitrate reductase in the yeast Hansenula anomala

Nitrate reduction and the isolation of Nit− mutants in Hansenula polymorpha

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