Response of Nitrogen Metabolism in Masson Pine Needles to Elevated CO2

Abstract

To explore the response of nitrogen metabolism in Masson pine (Pinus massoniana) to high CO2 concentrations, needles from one-year-old seedlings were used as materials to detect key enzyme activities, gene expression and different forms of nitrogen metabolites after CO2 stress for different durations (0 h, 6 h, 12 h, 24 h). The results show that elevated CO2 affected the efficiency of nitrogen metabolism in Masson pine needles, inhibiting the expression of key genes involved in nitrogen metabolism, including glutamate synthase (GOGAT), nitrite reductase (NiR), glutamine synthase (GS), nitrate reductase (NR) and glutamate dehydrogenase (GDH), and decreasing the activities of GOGAT, NiR, and GS. The decrease in enzyme activities and gene expression caused a decrease in different forms of nitrogen metabolites, including total nitrogen, ammonium, nitrite and specific amino acids. With prolonged stress, the nitrate content increased first and then decreased. In this study, the response pattern of nitrogen metabolism to CO2 stress in Masson pine needles was described, which may aid future research on nitrogen utilization in Masson pine.

Interaction of Nitrate Assimilation and Photorespiration at Elevated CO2

“…This link has also been shown by Häusler et al (1994) and Wallsgrove et al (1987), who reported that barley mutants lacking GS activity suffered under photorespiratory conditions. In addition, it is known that even short incubations at eCO 2 result in a reduction of GS and GOGAT activity (Guo et al, 2013;Wu et al, 2020). Our finding that the ratio of NR to GDC activity was elevated at eCO 2 in the wildtype as well as the mutant indicates that the GS/GOGAT cycle contained more newly assimilated N at eCO 2 , and this further argues against N starvation at eCO 2 .…”

Intersections: photosynthesis, abiotic stress, and the plant microbiome

“…Xiang et al (2020) reported differential expression of genes associated with nitrogen acquisition and assimilation in symbiotic algae growing within vs. outside of their nonphotosynthetic host, specifically algal genes for ammonium and nitrate transporters, nitrate reductase, and transporters for organic nitrogen compounds such as urea and purines. These same authors concluded that the symbiotic partners exhibited 'metabolic integration' between them, where nitrogen metabolism was 'decoupled' from photosynthesis in the photosynthetic partner in the sense that photosynthesis proceeded at high rates irrespective of nitrogen status by carbohydrate consumption by the nonphotosynthetic partner and associated relief of back-pressure into photosynthetic electron transport and prevention of excess ROS formation (Xiang et al 2020). Moreover, interaction of the plant rhizosphere microbiome with the plant's AOX was reported by Ortíz et al (2020).…”

“…Elevated CO2 concentrations initially stimulate nitrate reductase activity, which is associated with the enhanced production of redox messengers (nitric oxide and ROS; Bian et al 2020). These messengers can secondarily repress key genes in nitrogen metabolism, including nitrate reductase itself (Wu et al 2020; see also Shin andSchachtman 2004, Kim et al 2010), and can trigger plant senescence Sathee 2021a, Padhan et al 2020; see also Queval et al 2007, Krasensky-Wrzaczek andKangasjärvi 2018).…”

Growth and Nutritional Quality of Lemnaceae Viewed Comparatively in an Ecological and Evolutionary Context

“…Under these conditions, excessive ROS production in the chloroplast is combined with the production of additional oxidants in other cell compartments that participate in nitrate metabolism. Specifically, a high activity of the nitrate-reducing enzyme nitrate reductase produces high levels of messengers (both ROS and reactive nitrogen species, RNS; [99]) that modulate nitrogen metabolism [100][101][102] and can also trigger plant senescence ( [66,103]; see also [104,105]).…”