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

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