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Decreasing nitrogen (N) supply affected the normal growth of Oryza sativa (O. sativa) seedlings, reducing CO2 assimilation, stomatal conductance (gs), the contents of chlorophylls (Chl) and the ratio of Chl a/Chl b, but increasing the intercellular CO2 concentration. Polyphasic chlorophyll a fluorescence transient and relative fluorescence parameters (JIP test) results indicated that N deficiency increased Fo, but decreased the maximum quantum yield of primary photochemistry (Fv/Fm) and the maximum of the IPphase, implying that N-limiting condition impaired the whole photo electron transport chain from the donor side of photosystem II (PSII) to the end acceptor side of PSI in O. sativa. N deficiency enhanced the activities of the antioxidant enzymes, such as ascorbate peroxidase (APX), guaiacol peroxidase (GuPX), dehydro–ascorbate reductase (DHAR), superoxide dismutase (SOD), glutathione peroxidase (GlPX), glutathione reductase (GR), glutathione S-transferase (GST) and O-acetylserine (thiol) lyase (OASTL), and the contents of antioxidant compounds including reduced glutathione (GSH), total glutathione (GSH+GSSG) and non-protein thiol compounds in O. sativa leaves. In contrast, the enhanced activities of catalase (CAT), DHAR, GR, GST and OASTL, the enhanced ASC–GSH cycle and content of sulfur-containing compounds might provide protective roles against oxidative stress in O. sativa roots under N-limiting conditions. Quantitative real-time PCR (qRT-PCR) analysis indicated that 70% of the enzymes have a consistence between the gene expression pattern and the dynamic of enzyme activity in O. sativa leaves under different N supplies, whereas only 60% of the enzymes have a consistence in O. sativa roots. Our results suggested that the antioxidant system and sulfur metabolism take part in the response of N limiting condition in O. sativa, and this response was different between leaves and roots. Future work should focus on the responsive mechanisms underlying the metabolism of sulfur-containing compounds in O. sativa under nutrient deficient especially N-limiting conditions.

Plants exude strigolactones (SLs) to attract symbiotic arbuscular mycorrhizal fungi in the rhizosphere. Previous studies have demonstrated that phosphorus (P) deficiency, but not nitrogen (N) deficiency, significantly promotes SL exudation in red clover, while in sorghum not only P deficiency but also N deficiency enhances SL exudation. There are differences between plant species in SL exudation under P- and N-deficient conditions, which may possibly be related to differences between legumes and non-legumes. To investigate this possibility in detail, the effects of N and P deficiencies on SL exudation were examined in Fabaceae (alfalfa and Chinese milk vetch), Asteraceae (marigold and lettuce), Solanaceae (tomato), and Poaceae (wheat) plants. In alfalfa as expected, and unexpectedly in tomato, only P deficiency promoted SL exudation. In contrast, in Chinese milk vetch, a leguminous plant, and in the other non-leguminous plants examined, N deficiency as well as P deficiency enhanced SL exudation. Distinct reductions in shoot P levels were observed in plants grown under N deficiency, except for tomato, in which shoot P level was increased by N starvation, suggesting that the P status of the shoot regulates SL exudation. There seems to be a correlation between shoot P levels and SL exudation across the species/families investigated.

Background Eucalyptus is one of the most important fast-growing tree species in the world, and its growth and development are significantly affected by nitrogen and phosphorus. The Amino acid/auxin permease (AAAP) gene family plays key roles in long-distance amino acid transport in plants, but their evolutionary diversity and gene expression analysis in Eucalyptus grandis under nutrient deficiency stress are largely unexplored. Results This study presents the first genome-wide identification and functional characterization of 78 AAAP family genes (EgAAAPs) in Eucalyptus grandis , classified into eight subfamilies. Phylogenetic analysis of 28 species across five evolutionary stages revealed the AAAP family’s classification into three groups: Group III originating from green algae and Groups I-II from mosses. This study underscores lineage-specific expansions (e.g., Eucalyptus AAPs) and algal ancestors as pivotal drivers of functional diversification during early land plant adaptation. Structural analysis revealed subfamily-specific features, including conserved motifs, domain variations, and exon-intron heterogeneity, underpinning functional divergence. Tandem duplication dominated EgAAAP expansion, with syntenic conservation to Populus trichocarpa offering molecular insights into Myrtaceae - Salicaceae divergence. Transcriptional regulatory networks identified 166 transcription factors (MYBs, WRKYs, NACs), with subgroup-specific cis -element enrichment: WRKY binding in Group II and RGA-LIKE1 in Groups I/III, mechanistically linking phosphate/nitrogen signaling. Cross-species interaction hubs of key EgAAAPs (e.g., EgAAAP37, EgAAAP38, EgAAAP41, EgAAAP42, EgAAAP43 and EgAAAP78) with stress-responsive proteins (ABCG40, STP1), amino acid transporters (UMAMITs, CAT5/6), and metal carriers (YSLs) revealed woody plant-specific networks absent in Arabidopsis . Spatiotemporal expression profiling delineated six tissue-specific clusters and dynamic hormonal responses: SA/JA induced temporally distinct modules (early, sustained, delayed), while boron/nitrogen/phosphorus deficiency triggered subgroup- and tissue-dependent regulation. Conclusions Collectively, this study deciphers the evolutionary innovation, regulatory complexity, and functional specialization of AAAP transporters in Eucalyptus , providing a framework for understanding nutrient signaling and stress resilience in woody plants.

Nitrogen deficiency (−N) in plants triggers leaf senescence which is regulated by the transcription factor ORE1. Little is known about post-translational regulation of ORE1 in this process. Here, we show that UBP12/UBP13 (ubiquitin-specific protease 12/13) antagonize the action of NLA (nitrogen limitation adaptation) E3 ligase to maintain ORE1 homeostasis. In vitro pull-down and in vivo co-immunoprecipitation assays demonstrated specific binding between UBP12/UBP13 and ORE1. We further analyzed in various genotypes total Chl content and expression levels of senescence-related genes under −N conditions. We found that UBP12/UBP13 can deubiquitinate polyubiquitinated ORE1 in vitro and increase the stability of ORE1 in vivo in MG132/cycloheximide-chase experiments. Plants overexpressing UBP12/UBP13 display accelerated leaf senescence which is reversed by the ore1 mutation. By contrast, the senescence phenotype of plants overexpressing ORE1 is exacerbated by UBP12/UBP13 overexpression. The expression of senescence-related genes tracks the senescence phenotype. ORE1 protein levels can be elevated by UBP12/UBP13 overexpression but decreased in ubp12-2w/13-3. In conclusion, UBP12/UBP13 deubiquitinate ORE1 to stabilize this transcription factor and promote its activity as a positive regulator for leaf senescence under −N conditions. Our study shows that UBP12/UBP13 counteracts the effect of NLA E3 ligase to accelerate leaf senescence under nitrogen starvation.

Background Genetic variation in plant functional traits has been recognized as a potential avenue for enhancing nitrogen use efficiency (NUE) in wheat, which is a cost-effective strategy for reducing environmental burden of excessive N fertilizer application. In this study, a total of 126 diverse wheat genotypes originating from 16 countries were cultivated in pots supplied with a low N level at 10 mg kg − 1 to explore the functional traits determining NUE and their responses to N limitation. Results Under low N condition, significant genetic variations were observed in root morphological traits, photosynthesis capability and NUE among the wheat genotypes. The ranges of NUE and physiological NUE across 126 genotypes were 0.39–1.41 g mg − 1 and 0.39–1.26 g mg − 1 , respectively. Multivariate analysis revealed the examined root morphological traits were closely associated with plant N content, NUE and biomass accumulation under low N condition. Specially, roots with high root mass density (RMD) were beneficial to improve NUE, while high specific root length (SRL) and specific root surface area (SRA) were positively correlated with plant N concentration in response to N limitation. In contrast, photosynthesis traits exerted little effect on NUE in wheat at early growth stage under low N condition. Conclusion Root morphological traits were superior to photosynthesis capacity in mediating wheat response to low N condition. Notably, RMD holds promise for application in breeding programs aimed at improving NUE in wheat.

Background Agricultural yield is closely associated with nitrogen application. Thus, reducing the application of nitrogen without affecting agricultural production remains a challenging task. To understand the metabolic, physiological, and morphological response of wheat ( Triticum aestivum ) to nitrogen deficiency, it is crucial to identify the genes involved in the activated signaling pathways. Results We conducted a hydroponic experiment using a complete nutrient solution (N1) and a nutrient solution without nitrogen (N0). Wheat plants under nitrogen-deficient conditions (NDC) showed decreased crop height, leaf area, root volume, photosynthetic rate, crop weight, and increased root length, root surface area, root/shoot ratio. It indicates that nitrogen deficiency altered the phenotype of wheat plants. Furthermore, we performed a comprehensive analysis of the phenotype, transcriptome, GO pathways, and KEGG pathways of DEGs identified in wheat grown under NDC. It showed up-regulation of Exp (24), and Nrt (9) gene family members, which increased the nitrogen absorption and down-regulation of Pet (3), Psb (8), Nar (3), and Nir (1) gene family members hampered photosynthesis and nitrogen metabolism. Conclusions We identified 48 candidate genes that were involved in improved photosynthesis and nitrogen metabolism in wheat plants grown under NDC. These genes may serve as molecular markers for genetic breeding of crops.

Leaf nitrogen allocation and photosynthetic proteins response can affect net photosynthetic rate (Pn), ultimately influencing crop yield under diverse environmental stresses. However, the internal relationship between Pn with leaf nitrogen allocation and photosynthetic proteins response under nitrogen or water scarcity in peanut ( Arachis hypogaea L.) remains elusive. Here, comprehensive physiological property and proteomic analyses of peanut were conducted, revealing that both nitrogen and water scarcity remarkably impeded leaf growth and reduced Pn. Nitrogen deficiency significantly reduced the total nitrogen content per unit leaf area (N area ), chlorophyll content, and Pn, whereas drought stress caused a greater decline in photosynthetic nitrogen use efficiency (PNUE). The allocation of leaf nitrogen to photosynthetic components, including the carboxylation system and electron transport system in leaves, was significantly reduced when subjected to individual or combined deficiency. Proteomic analyses exhibited that several key photosynthetic proteins underwent a decrease under both single and combined water and nitrogen deficiency conditions. Thereby, Pn may decline due to the disruption of nitrogen allocation and down-regulated expression of photosynthetic proteins under these stress conditions. Our findings establish a benchmark for future research exploring the roles of leaf nitrogen allocation and photosynthetic proteins in the plant’s response to nitrogen or water deficiency.

Strigolactones (SLs) are essential host recognition signals for both root parasitic plants and arbuscular mycorrhizal fungi, and SLs or their metabolites function as a novel class of plant hormones regulating shoot and root architecture. Our previous study indicated that nitrogen (N) deficiency as well as phosphorus (P) deficiency in sorghum enhanced root content and exudation of 5-deoxystrigol, one of the major SLs produced by sorghum. In the present study, we examined how N and P fertilization affects SL production and exudation in sorghum plants subjected to short- (5 days) or long-term (10 days) N or P deficiency and demonstrated their common and distinct features. The root contents and exudation of SLs in the N- or P-deficient sorghum plants grown for 6, 12 or 24 h with or without N or P fertilization were quantified by LC–MS/MS. In general, without fertilization, root contents and exudation of SLs stayed at similar levels at 6 and 12 h and then significantly increased at 24 h. The production of SLs responded more quickly to P fertilization than the secretion of SLs, while regulation of SL secretion began earlier after N fertilization. It is suggested that sorghum plants regulate SL production and exudation when they are subjected to nutrient deficiencies depending on the type of nutrient and degree of deficiency.

Background Nitrogen (N) fertilizer is commonly considered as one of the most important limiting factors in the agricultural production. As a result, a large amount of N fertilizer is used to improve the yield in modern tea production. Unfortunately, the large amount of N fertilizer input has led to increased plant nitrogen-tolerance and decreased amplitude of yield improvement, which results in significant N loss, energy waste and environment pollution. However, the effects of N-deficiency on the metabolic profiles of tea leaves and roots are not well understood. Results In this study, seedlings of Camellia sinensis (L.) O. Kuntze Chunlv 2 were treated with 3 mM NH 4 NO 3 (Control) or without NH 4 NO 3 (N-deficiency) for 4 months by sandy culture. The results suggested that N-deficiency induced tea leaf chlorosis, impaired biomass accumulation, decreased the leaf chlorophyll content and N absorption when they were compared to the Control samples. The untargeted metabolomics based on GC-TOF/MS approach revealed a discrimination of the metabolic profiles between N-deficient tea leaves and roots. The identification and classification of the altered metabolites indicated that N deficiency upregulated the relative abundances of most phenylpropanoids and organic acids, while downregulated the relative abundances of most amino acids in tea leaves. Differentially, N-deficiency induced the accumulation of most carbohydrates, organic acids and amino acids in tea roots. The potential biomarkers screened in N-deficient leaves compared to Control implied that N deficiency might reduce the tea quality. Unlike the N-deficient leaves, the potential biomarkers in N-deficient roots indicated an improved stress response might occur in tea roots. Conclusions The results demonstrated N deficiency had different effects on the primary and secondary metabolism in tea leaves and roots. The findings of this study will facilitate a comprehensive understanding of the N-deficient tea plants and provide a valuable reference for the optimized N nutrient management and the sustainable development in the tea plantations.

Background Nitrogen (N) deficiency is a major constraint for plant production in many areas. Developing the new crop genotypes with high productivity under N deficiency is an important approach to maintain agricultural production. Therefore, understanding how plant response to N deficiency and the mechanism of N-deficiency tolerance are very important for sustainable development of modern crop production. Results In this study, the physiological responses and fatty acid composition were investigated in 24 wheat cultivars under N-deficient stress. Through Pearson’s correlation analysis and principal component analysis, the responses of 24 wheat cultivars were evaluated. The results showed that the plant growth and carbohydrate metabolism were all differently affected by N deficiency in all tested wheat cultivars. The seedlings that had high shoot biomass also maintained high level of chlorophyll content under N deficiency. Moreover, the changes in fatty acid composition, especially the linolenic acid (18:3) and the double bond index (DBI), showed close positive correlations with the shoot dry weight and chlorophyll content alterations in response to N-deficient condition. These results indicated that beside the chlorophyll content, the linolenic acid content and DBI may also contribute to N-deficiency adaptation, thus could be considered as efficient indicators for evaluation of different response in wheat seedlings under N-deficient condition. Conclusions The alteration in fatty acid composition can potentially contribute to N-deficiency tolerance in plants, and the regulation of fatty acid compositions maybe an effective strategy for plants to adapt to N-deficient stress.