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).
Talk
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 density off resources proteins were quantified for every single cures in order to check if GABA entered the root and to dictate you are able to correlation between endogenous amino acidic account and you will nitrate increase otherwise Nrt2 mRNA height (Table 1). Once twelve h of exogenous supply, endogenous intensity of for each amino acid used increased regarding the resources. Instance, 1 m meters GABA treatment increased sources GABA by dos.24-fold weighed against new handle flowers (Table 1). Yet not, 100 µ yards GABA and you will step 1 m m Glu treatments were not successful to increase levels amounts of all of the five proteins applied (Dining table step 1). No correlation try located between changes away from increase or BnNrt2 transcript accounts and you can supply amino acid concentrations or ratio between them.
- Thinking found will be the a style of three separate replicates ± SD of your own suggest.
Matchmaking ranging from glutamine in phloem latex and you may nitrate consumption throughout the N-starvation as well as the organization duration
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 ). best place in Canada for herpes dating 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.