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Planta. 2001 Jun;213(2):265-71.

Glutamine and alpha-ketoglutarate are metabolite signals involved in nitrate reductase gene transcription in untransformed and transformed tobacco plants deficient in ferredoxin-glutamine-alpha-ketoglutarate aminotransferase.

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Unité de Nutrition Azotée des Plantes, INRA de Versailles, France.


Transformed tobacco (Nicotiana tabacum L.) plants with varying activities of the key enzyme of ammonia assimilation, ferredoxin-glutamine-alpha-ketoglutarate aminotransferase (Fd-GOGAT; EC, were used to examine the roles of ammonium, glutamine (Gln) and alpha-ketoglutarate (alpha-KG) in the regulation of nitrate reductase (NR; EC transcript abundance. In wild-type leaf discs, NR mRNA abundance was increased following feeding with NO3-, sucrose and alpha-KG and decreased by feeding Gln. In air, leaves with decreased GOGAT accumulated Gln and alpha-KG simultaneously; this was accompanied by increased NR transcripts. The inhibition of NR transcription by Gln observed in leaf-disc experiments was therefore not observed in the low-Fd-GOGAT plants that accumulate Gln in vivo. The results suggest that the negative effect of Gln on NR transcript abundance was offset by high alpha-KG and that the relative amounts of alpha-KG and Gln are more important in controlling NR gene transcription than the concentration of either metabolite alone.

[Indexed for MEDLINE]

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