Negative effects of exogenous way to obtain GABA <a href=""></a>, Gln, Glu and you will Asn towards the nitrate consumption

In order to test the hypothesis that GABA could up-regulate nitrate uptake, the effect of exogenous supply of different amino acids was compared with control plants. Gln, Glu and Asn are known to act as inhibitors of nitrate uptake at the millimolar range in many species when supplied to the root nutrient solution ( Muller & Touraine 1992 ; Vid ). Therefore, roots were supplied with either 1 m m Gln, 1 m m Glu or 1 m m Asn, whereas two concentrations were tested for the GABA treatment, 100 µ m and 1 m m (Fig. 5). A positive and significant effect on 15 NO3 – influx was observed for 100 µ m (P < 0.05) and no significant effect for 1 m m GABA (P > 0.05)-treated plants compared with the control plants, whereas 15 NO3 – influx was significantly reduced by the Gln, Glu and Asn root treatments (Fig. 5a). The strongest negative effect on nitrate uptake was due to Glu (38% inhibition) followed by Asn (37% inhibition) and Gln (33% inhibition). In parallel, Northern blot analyses performed with mRNA extracted from the same amino acid treated plants confirmed previous results for all of the amino acids tested. Thus, BnNrt2 mRNA abundance was enhanced by 1.6- and 1.3-fold in response to 100 µ m and 1 m m GABA treatments, respectively. The Gln, Glu and Asn treatments reduced BnNrt2 mRNA abundance by 0.5-, 0.9- and 0.8-fold, respectively (Figs 5b & c).


Effects of exogenous supply of GABA, Gln, Glu and Asn on nitrate influx (a) and BnNrt2 gene expression (b and c) on 12 h nitrate deprived plants. Plants were supplied with 1 m m nitrate plus either 100 µ m or 1 m m GABA, 1 m m Gln, 1 m m Glu or 1 m m Asn for 12 h before measurement of 15 NO3 – influx and BnNrt2 transcript abundance. Influx and BnNrt2 transcript expression values are the means of six and two pots of 25 plants, respectively. Vertical bars indicate ± SE of the mean for n = 6 when larger than the symbol.

Endogenous levels out-of sources proteins had been quantified for each cures so you’re able to find out if GABA entered the underlying and to determine you are able to correlation ranging from endogenous amino acidic profile and nitrate increase otherwise Nrt2 mRNA peak (Desk step one). Immediately following a dozen h regarding exogenous also provide, endogenous intensity of each amino acidic used improved on the supply. Such as, step one meters yards GABA treatment enhanced sources GABA by dos.24-bend compared with the fresh manage vegetation (Table 1). Yet not, 100 µ m GABA and step one m yards Glu treatments were unsuccessful to increase density degrees of all four proteins applied (Desk step one). No correlation is actually receive ranging from changes out-of increase or BnNrt2 transcript accounts and means amino acidic levels or ratio between the two.

  • Values revealed is the manner of around three separate replicates ± SD of one’s mean.

Matchmaking between glutamine for the phloem latex and you will nitrate consumption during Letter-starvation and over the organization cycle

It is well established that N-deprivation leads to a transient ‘de-repression’ of high-affinity nitrate influx and Nrt2 gene expression in plants with a low N status ( Lejay et al. 1999 ; Forde 2002 ). In plants with a high N status, ‘de-repression’ seems to be bypassed, leading to a direct decline of nitrate uptake interpreted as ‘de-induction’ ( Clarkson 1986 ; Siddiqi et al. 1989 ; Faure-Rabasse et al. 2002 ). Our results for 15 NO3 – influx and BnNrt2 gene expression (Fig. 1a & c) are consistent with these previous studies.