Nitrate Reductase Modulation in Response to Changes in C/N Balance and Nitrogen Source in Arabidopsis

Abstract

Environmental cues modulate the balance of carbon (C) and nitrogen (N) which are essential elements for plant metabolism and growth. In Arabidopsis, photochemical efficiency of PSII, phosphorylation status and localization of many enzymes, and the level of total soluble sugars were affected by an unbalanced C/N ratio. Since differences in C/N affect these parameters, here we checked whether different sources of N have different effects when a high C/N ratio is imposed. NO3- and NH4+ were separately provided in C/N medium. We investigated the effects on photochemical efficiency of PSII, the level of total soluble sugars and nitrate reductase activity under stressful C/N conditions compared with control conditions. We found that treated plants accumulated more total soluble sugars when compared with control. Photochemical efficiency of PSII did not show significant differences between the two sources of nitrogen after 24 h. The actual nitrate reductase activity was the result of a combination of activity, activation state and protein level. This activity constantly decreased starting from time zero in control conditions; in contrast, the actual nitrate reductase activity showed a peak at 2 h after treatment with NO3-, and at 30 min with NH4+. This, according to the level of total soluble sugars, can be explained by the existence of a cross-talk between the sugars in excess and low nitrate in the medium that blocks the activity of nitrate reductase in stressful sugar conditions until the plant is adapted to the stress.

Response of Nitrogen Metabolism in Masson Pine Needles to Elevated CO2

“…Notably, when Vicente [49] studied the response mode of durum wheat nitrogen metabolism genes under the stress of nitrogen supply, temperature and CO 2 , he found that elevated CO 2 , atmospheric temperature and low N supply could induce the expression of GS and Fd-GOGAT with an upregulated trend, while the expression of other genes was inhibited. We speculated that the cross-talk mechanism between different stresses was the reason for this finding [50]. On the other hand, when we analyzed the correlation between genes and enzyme activities, we found that the enzyme activity and gene expression levels of NiR, GS and GOGAT showed a similar trend.…”

Transcription strategies related to photosynthesis and nitrogen metabolism of wheat in response to nitrogen deficiency

“…8 b, d). DEGs belonging to Nar (nitrate reductase) gene family were involved in the nitrate-N reduction to nitrite-N process [ 26 , 27 ]. DEGs belonging to Nir (Nitrite reductase) gene family were involved in the nitrite-N reduction to the ammonium-N process [ 28 , 29 ].…”

Protein Phosphorylation Dynamics Under Carbon/Nitrogen-Nutrient Stress and Identification of a Cell Death-Related Receptor-Like Kinase in Arabidopsis

“…Our previous study showed that high C/low N-nutrient status, resulting from elevated atmospheric CO 2 concentration and limited nitrogen availability, promoted leaf senescence (Aoyama et al, 2014). We also identified several components mediating C/N-nutrient signaling and revealed that altered protein phosphorylation is strongly involved in responses to plant C/N-nutrient imbalance (Maekawa et al, 2012;Yasuda et al, 2014Yasuda et al, , 2017Lu et al, 2015;Huarancca Reyes et al, 2015;Huarancca Reyes et al, 2018). However, comprehensive phosphorylation dynamics responsive to C/Nnutrient availability, including proteins targeted by 14-3-3, were unclear.…”