Nitrogen‐Centric Molecular Mechanisms in Crop Plants Under Elevated CO2: Interactions, Responses, and Implications

Nitrogen use efficiency in crops under salt stress: from molecular networks to intelligent breeding

A four-tier closed-loop conceptual framework comprising signal perception, transport reprogramming, metabolic redistribution, and genetic redesign is developed that yields three testable predictions: the sequential activation of regulatory tiers; a quantitative relationship between Ca2+ signal amplitude and the extent of C–N metabolic redistribution; and salt-concentration thresholds that distinguish basal homeostatic buffering from full adaptive reprogramming.

Post-Translational Control of Nitrate Reductase Under Elevated CO2 in Solanum lycopersicum: Carbon–Nitrogen Signaling and Photosynthetic Acclimation

Rising atmospheric CO2 is altering carbon–nitrogen interactions in C3 crops, with tomato (Solanum lycopersicum L.) showing enhanced carbon assimilation but frequently reduced nitrogen acquisition and assimilation. Nitrate reductase (NR), the rate-limiting enzyme in nitrate reduction, plays a central role by integrating nitrate assimilation with carbon metabolism and nitric oxide (NO) signaling. This review summarizes current knowledge of NR regulation in tomato under elevated CO2 (eCO2), focusing on post-translational mechanisms and their contribution to photosynthetic acclimation. Elevated CO2 modulates NR activity through interconnected changes in photorespiration, carbohydrate-mediated feedback, redox regulation, source–sink dynamics, and nitrogen availability. While eCO2 generally suppresses leaf nitrate assimilation by reducing photorespiratory support, root-zone CO2 enrichment can transiently stimulate root NR activity, highlighting tissue-specific regulation. Multi-omics studies further demonstrate extensive metabolic and molecular reprogramming affecting carbon skeleton supply, amino acid biosynthesis, and nitrogen assimilation. In addition, NR-dependent NO production links nitrogen metabolism with stomatal regulation through ABA-independent H2O2–NO signaling. Despite these advances, the roles of NR phosphorylation, 14-3-3 protein interactions, and redox-mediated regulation under eCO2 remain poorly understood. Overall, NR functions as a key metabolic and signaling hub coordinating carbon and nitrogen metabolism under future climate conditions. Understanding these regulatory mechanisms will facilitate strategies to improve nitrogen-use efficiency, sustain photosynthesis, and enhance tomato productivity under elevated atmospheric CO2 while identifying priorities for future physiological, molecular, and multi-omics research.

Adaptation mechanisms of low-phosphorus stress in plants: physiological responses, molecular regulation, and future perspectives

The molecular regulatory networks governing plant responses to low-Pi stress, covering phosphate transporters, SPX-PHR signaling, transcription factors, non-coding RNAs, and epigenetic modifications are summarized.

The carbon-nitrogen metabolism gene E1OGDH1 influences maize root system architecture and nitrogen plasticity

Synthetic nitrogen fertilizers have greatly increased crop yields, yet much of the applied nitrogen is lost from agroecosystems and contributes to environmental pollution and higher economic costs. Improving nitrogen uptake efficiency (NUpE) benefits from understanding how root system architecture (RSA) governs soil nitrogen capture. Although root traits have seldom been explicit breeding targets, selection for variation in above-ground nitrogen accumulation has also likely shaped differences in RSA. The Illinois Protein Strain Recombinant Inbred population, derived from more than a century of divergent selection for seed protein concentration, offers a powerful resource for dissecting RSA variation. Using multi-year field phenotyping of excavated root crowns and genome-wide association analysis, we identified a quantitative trait locus on chromosome 10 containing E1OGDH1, which encodes the E1 subunit of the 2-oxoglutarate dehydrogenase (OGDH) complex. OGDH performs a key step in the tricarboxylic acid cycle that also modulates 2-oxoglutarate, an important entry point into nitrogen metabolism and a co-factor for enzymes involved in hormone and secondary product synthesis. Long-read sequencing of inbreds derived from the divergent IHP and ILP parental populations revealed promoter polymorphisms defining E1OGDH1 alleles and differed in E1OGDH1 expression in root tissue. Field experiments in IPSRI lines carrying IHP- or ILP-associated E1OGDH1 alleles showed differences in root architectural traits over two years. CRISPR-Cas9 knockout mutants confirmed a functional role for E1OGDH1 in whole-plant performance and nitrogen-responsive root development. Mutants were shorter, had reduced biomass, and exhibited altered architectural responses to soil nitrogen levels. Transcriptome analysis further showed that loss of E1OGDH1 altered basal and nitrogen-responsive expression of genes associated with root development and nitrogen uptake and metabolism. Together, these findings identify E1OGDH1 as a strong candidate quantitative regulator of maize RSA and nitrogen plasticity, suggesting that central carbon–nitrogen metabolic genes can contribute to root developmental responses relevant to NUpE.

Design Principles of Plant Thermotolerance: Integrating Photosynthesis, Reproduction, and Field Resilience in a Warming Climate.

Global food security is increasingly threatened by climate change, as rising temperatures compromise the yields of major staple crops, including wheat, rice, and maize. Enhancing plant thermotolerance has therefore become a critical priority for sustaining agricultural productivity. However, plant heat-stress responses have often been described as fragmented and pathway-specific, limiting their translation into effective crop improvement strategies. Here, we synthesize current knowledge of plant responses to heat stress and reframe them as an integrated set of design principles centered on preserving photosynthetic carbon gain under high temperature. By doing so, we provide a collection of insights that may help guide future research efforts and the development of strategies for improving plant thermotolerance. We organize major defense strategies into six functional domains: (i) membrane systems and structural integrity, (ii) photosynthetic regulation, (iii) protective metabolites and hormonal signaling, (iv) reactive oxygen species (ROS) scavenging, (v) protein homeostasis, and (vi) transcriptional and post-transcriptional regulation. Rather than treating these responses as independent pathways, we emphasize their temporal hierarchy, energetic costs, and functional interconnections, highlighting their shared objective-maintaining CO2 assimilation, energy balance, and biomass accumulation as thermal damage accelerates. We further discuss how insights from mutagenesis, transgenic approaches, and targeted genetic modification can be translated into crop improvement, clarifying opportunities and trade-offs that emerge when thermotolerance is engineered at distinct physiological nodes. Together, this design-centered framework provides a unifying conceptual and practical roadmap for developing high-yielding, heat-tolerant cultivars, offering actionable guidance for sustaining crop productivity in a warming world.

AspAT orchestrates metabolic and transcriptional networks for drought adaptation in poplar.