05 Aug Effects of exogenous source of GABA, Gln, Glu and you will Asn to the nitrate uptake
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 NOstep three – 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).
Discussion
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 away from supply proteins was quantified for each and every medication so you can check if GABA entered the underlying in order to dictate you can easily correlation between endogenous amino acid levels and you can nitrate increase otherwise Nrt2 mRNA level (Desk step 1). Shortly after 12 h out-of exogenous also provide, endogenous intensity of for each amino acidic used increased on the sources. Such, 1 yards m GABA cures improved means GABA from the dos.24-bend compared with the fresh new control flowers (Dining table 1). But not, a hundred µ meters GABA and you may 1 yards yards Glu services failed to improve concentrations degrees of all of the four proteins applied (Table 1). No correlation are discover anywhere between alter regarding influx or BnNrt2 transcript account and you may supply amino acidic density otherwise ratio between them.
- Opinions revealed would be the technique of about three independent replicates ± SD of your own imply.
Relationship anywhere between glutamine within the phloem latex and you will nitrate consumption bbw online dating Australia throughout N-starvation as well as the development stage
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.
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