Effect of Exogenous Ammonium on GlutamineSynthetase, Glutamate Synthase, and Glutamate Dehydrogenase in the Root of Rice Seedling

Root biomass of rice seedlings was increased at lower concentration of exogenous NH 4 + , but it was decreased at higher concentration of exogenous NH 4 + . The level of free NH 4 + in the roots was accumulated gradually with the increase of NH 4 + concentration in the nutrient solution. The content of the soluble proteins was essentially constant at higher NH 4 + . The activities of glutamine synthetase (GS), NADH-dependent glutamate synthase (NADH-GOGAT), and NADH-dependent glutamate dehydrogenase (NADH-GDH) were risen with exogenous NH 4 + concentration at the lower NH 4 + concentration range. But the activities of GS and NADH-GOGAT were declined, and the level of NADH-GDH activity was kept constant under higher NH 4 + concentration. The GS/GDH ratio suggested that NH 4 + was assimilated by GS-GOGAT cycle under lower NH 4 + concentration, but NADH-GDH was more important for NH 4 + assimilation and detoxifying NH 4 + to the tissue cells at the higher NH 4 + level. According to the growth and the activity changes of these ammonium-assimilating enzymes of rice seedling roots, 10. 0 μg/mL NH 4 + -N in nutrient solution was more suitable to the rice growth.

Research on Glutamate Synthase Activity in Sugar Beet(Beta Vulgaris L.)under Different Levels of Nitrogen

The experiment of glutamate synthase activity (GOGATA) in both leaf blades and roots under different nitrogen levels was carried out at Northeast Agricultural University in 1993. The result showed that GOGATA rose rapidly to reach its peak from seedling stage to foliage rapid growth stage, and then declined gradually. GOGATA was enhanced with increasing nitrogen levels and had significant positive correlation with nitrogen levels at the middle stage of growth GOGATA in leaf blades was the strongest compared with crowns, petioles and roots, thus, it could represent the highest enzyme activity of the whole plant. GOGATA had quadratic curvilinear correlation with root yield and sugar production. GOGATA in leaf blades had significant positive correlation with α-NH 2-N at the foliage rapid growth stage while GOGATA in roots existed this relation at the latter stage of growth. GOGATA in roots had significant negative correlation with sugar content at harvest.

Differential Effect of Aluminium on Enzymes of Nitrogen Assimilation in Excised Bean Leaf Segments

Aluminium is a potent toxicant in acidic soils. The present study was taken up to analyze the effects of Al on enzymes of nitrogen assimilation in excised bean (Phaseolus vulgaris) leaf segments so as to gain an insight of the mechanism involved. Supply of 0.001 to 0.1 mM AlCl3 to excised bean leaf segments affected the in vivo nitrate reductase activity differently in the presence of various inorganic nitrogenous compounds, being inhibited with 5 mM ammonium nitrate and 10 mM ammonium chloride but enhanced with 10 mM potassium nitrate. Al effect with 50 mM KNO3 varied with time, showing an increased activity at shorter duration, but decreased at longer duration. Al effect on in vivo NRA was dependent upon the nitrate concentration, thus, inhibiting it at 0, 1 and 50 mM KNO3, while increasing at 2 and 10 mM. Further, saturating and non-saturating effects were observed in the absence and presence of Al. Al supply influenced the in vitro NRA also, being increased at 10 mM, but decreased at 50 mM KNO3. Supply of Al to excised leaf segments substantially inhibited the glutamate dehydrogenase activity in the absence as well as presence of 5 mM NH4NO3 but increased the glutamate synthase activity. Inhibition of specific glutamate dehydrogenase activity by Al supply was also observed. However, specific glutamate synthase activity was increased in the presence of NH4NO3 only. The experiments demonstrated that effect of supply of aluminium on in vivo nitrate reductase activity depended upon nitrogenous source as well as nitrate concentration and it exerted reciprocal regulation of glutamate dehydrogenase and glutamate synthase activities, which depended upon N supply too.

Analysis of Nitrogen Metabolism Related Enzymes and Related Physiological Indexes of Main Foxtail Millet Varieties Developed in North China

[Objectives] This study was conducted to clarify the evolution characteristics of foxtail millet varieties in different ages and provide a basis for the breeding of new varieties. [Methods] A field experiment was carried out on 20 main foxtail millet varieties promoted in North China developed from the 1980 s to 2000 s. The physiological and biochemical indexes of different foxtail millet varieties in four ages were compared, including chlorophyll content, soluble protein content, glutamine synthetase(GS) activity and glutamate synthase(GOGAT) activity, and the correlation between enzyme activity and yield was analyzed. [Results] The chlorophyll SPAD values of the flag leaf and functional leaves of foxtail millet varieties decreased with the filling process. The SPAD values of the flag leaf, top second leaf and top third leaf were higher in the varieties developed in the 1990 s and 2000 s than those in the 1980 s and 2010 s. The activity of glutamine synthetase(GS) and glutamate synthase(GOGAT) showed a single-peak curve in different foxtail millet varieties developed in the recent 30 years, and the peaks of the two were at 7 d and at 7 or 14 d, respectively. The activity of GS and GOGAT increased with the breeding age. In the period from 7 d after anthesis to the mature period, the decreases in the soluble protein content followed an order of 2010 s, 2000 s, 1990 s and 1980 s from small to large, indicating that the degradation rate of various enzyme sources and metabolic regulators in foxtail millet plants decreased during the improvement process. At 35 d after anthesis, the correlation coefficient between GS activity and yield was-0.247, that is, there was a negative correlation with yield. And there was a significant positive correlation between GOGAT activity and yield, and the correlation coefficient was as high as 0.455 at 7 d after anthesis. [Conclusions] Changes in the GS activity, GOGAT activity and soluble protein content in the flag leaf of foxtail millet varieties developed in recent years have a certain impact on yield.

Information entropy-based fitting of the disease trajectory of brain ischemia-induced vascular cognitive impairment

The present study investigated the disease trajectory of vascular cognitive impairment using the entropy of information in a neural network mathematical simulation based on the free radical and excitatory amino acids theories. Glutamate, malondialdehyde, and inducible nitric oxide synthase content was significantly elevated, but acetylcholine, catalase, superoxide dismutase, glutathione peroxidase and constitutive nitric oxide synthase content was significantly decreased in our vascular cognitive impairment model. The fitting curves for each factor were obtained using Matlab software. Nineteen, 30 and 49 days post ischemia were the main output time frames of the influence of these seven factors. Our results demonstrated that vascular cognitive impairment involves multiple factors. These factors include excitatory amino acid toxicity and nitric oxide toxicity. These toxicities disrupt the dynamic equilibrium of the production and removal of oxygen free radicals after cerebral ischemia, reducing the ability to clear oxygen free radicals and worsening brain injury.

Nitrogen starvation induces genome-wide activation of transposable elements in Arabidopsis

Nitrogen(N)availability is a major limiting factor for plant growth and agricultural productivity.Although the gene regulation network in response to N starvation has been extensively studied,it remains unknown whether N starvation has an impact on the activity of transposable elements(TEs).Here,we report that TEs can be transcriptionally activated in Arabidopsis under N starvation conditions.Through genetic screening of idm1-14 suppressors,we cloned GLU1,which encodes a glutamate synthase that catalyzes the synthesis of glutamate in the primary N assimilation pathway.We found that glutamate synthase 1(GLU1)and its functional homologs GLU2 and glutamate transport 1(GLT1)are redundantly required for TE silencing,suggesting that N metabolism can regulate TE activity.Transcriptome and methylome analyses revealed that N starvation results in genome-wide TE activation without inducing obvious alteration of DNA methylation.Genetic analysis indicated that N starvationinduced TE activation is also independent of other well-established epigenetic mechanisms,including histone methylation and heterochromatin decondensation.Our results provide new insights into the regulation of TE activity under stressful environments in planta.