Low Nitrogen Stress Research Articles

Genome-Wide and Transcriptome Analysis of Autophagy-Related ATG Gene Family and Their Response to Low-Nitrogen Stress in Sugar Beet

Sugar beet (Beta vulgaris L.) is a significant global crop for sugar production, with nitrogen playing a crucial role in its growth, development, and sugar yield. Autophagy facilitates nutrient reabsorption and recycling under nutrient stress by degrading intracellular components, thereby enhancing plant nitrogen use efficiency. However, research on the autophagy response to low-nitrogen stress in sugar beet remains limited. In this study, 29 members of the ATG gene family were identified, with genes within the same subfamily displaying similar gene structures and conserved domains. These ATG genes in sugar beet contain various hormone and stress-response elements. Transcriptome data and qRT-PCR analysis further revealed that the expression levels of ATG4, ATG8b, ATG18a, TOR, NBR1, ATI, ATG8a, ATG12, and VTI12a were significantly upregulated under low-nitrogen stress, with most genes showing high expression levels across different tissues. These ATG genes are thus likely involved in regulating autophagy in response to low-nitrogen conditions. The observed increase in autophagosome numbers further supports the induction of autophagy by low-nitrogen stress. These nine genes can be considered key candidates for further research on nitrogen-sensitive autophagy in the sugar beet ATG gene family. This study provides a comprehensive analysis of the structure and biological functions of ATG genes in sugar beet, offering genetic resources for future efforts to improve sugar beet varieties through genetic engineering. Such efforts could focus on regulating autophagy to enhance nitrogen use efficiency and develop new germplasm.

Genome-Wide Characterization of Alfin-like Genes in Brassica napus and Functional Analyses of BnaAL02 and BnaAL28 in Response to Nitrogen and Phosphorus Deficiency.

Alfin-like proteins (ALs) form a plant-specific transcription factor (TF) gene family involved in the regulation of plant growth and development, and abiotic stress response. In this study, 30 ALs were identified in Brassica napus ecotype 'Zhongshuang 11' genome (BnaALs), and unevenly distributed on 15 chromosomes. Structural characteristic analysis showed that all of the BnaALs contained two highly conserved domains: the N terminal DUF3594 domain and the C-terminal PHD-finger domain. The BnaALs were classified into four groups (Group I-IV), supported by conserved intron-exon and protein motif structures in each group. The allopolyploid event between B. oleracea and B. rapa ancestors and the small-scale duplication events in B. napus both contributed to the large BnaALs expansion. The promoter regions of BnaALs contained multiple abiotic stress cis-elements. The BnaALs in I-IV groups were mainly expressed in cotyledon, petal, root, silique, and seed tissues, and the duplicated gene pairs shared highly similar expression patterns. RNA-seq and RT-qPCR analysis showed that BnaALs were obviously induced by low nitrogen (LN) and low phosphorus (LP) treatments in roots. Overexpressing BnaAL02 and BnaAL28 in Arabidopsis demonstrated their functions in response to LN and LP stresses. BnaAL28 enhanced primary roots' (PRs) length and lateral roots' (LRs) number under LP and LN conditions, where BnaAL02 can inhibit LR numbers under the two conditions. They can promote root hair (RH) elongation under LP conditions; however, they suppressed RH elongation under LN conditions. Our result provides new insight into the functional dissection of this family in response to nutrient stresses in plants.

Transcription factors BZR1 and PAP1 cooperate to promote anthocyanin biosynthesis in Arabidopsis shoots.

Anthocyanins play critical roles in protecting plant tissues against diverse stresses. The complicated regulatory networks induced by various environmental factors modulate the homeostatic level of anthocyanins. Here, we show that anthocyanin accumulation is induced by brassinosteroids (BRs) in Arabidopsis (Arabidopsis thaliana) shoots and shed light on the underlying regulatory mechanism. We observed that anthocyanin levels are altered considerably in BR-related mutants, and BRs induce anthocyanin accumulation by upregulating the expression of anthocyanin biosynthetic genes. Our genetic analysis indicated that BRASSINAZOLE RESISTANT 1 (BZR1) and PRODUCTION OF ANTHOCYANIN PIGMENT 1 (PAP1) are essential for BR-induced anthocyanin accumulation. The BR-responsive transcription factor BZR1 directly binds to the PAP1 promoter, regulating its expression. In addition, we found that intense anthocyanin accumulation caused by the pap1-D-dominant mutation is significantly reduced in BR mutants, implying that BR activity is required for PAP1 function after PAP1 transcription. Moreover, we demonstrated that BZR1 physically interacts with PAP1 to cooperatively regulate the expression of PAP1-target genes, such as TRANSPARENT TESTA 8, DIHYDROFLAVONOL 4-REDUCTASE, and LEUKOANTHOCYANIDIN DIOXYGENASE. Our findings indicate that BZR1 functions as an integral component of the PAP1-containing transcription factor complex, contributing to increased anthocyanin biosynthesis. Notably, we also show that functional interaction of BZR1 with PAP1 is required for anthocyanin accumulation induced by low nitrogen stress. Taken together, our results demonstrate that BR-regulated BZR1 promotes anthocyanin biosynthesis through cooperative interaction with PAP1 of the MBW complex.

Exploring the Molecular Landscape of Nitrogen Use Efficiency in Potato (Solanum tuberosum L.) under Low Nitrogen Stress: A Transcriptomic and Metabolomic Approach

Enhancing crop nitrogen use efficiency (NUE) in agricultural sciences is a pivotal challenge, particularly for high-demand crops like potatoes (Solanum tuberosum L.), the world’s third most significant food crop. This study delves into the molecular responses of potatoes to low nitrogen (LN) stress, employing an integrative approach that combines transcriptomics and metabolomics to compare two cultivars with divergent NUE traits: XS6, known for its high NUE, and NS7, characterized by lower NUE. Our research unveils that XS6 exhibits higher chlorophyll and N content, increased tuber yield, and elevated N assimilation capacity under LN stress conditions compared to NS7. Through transcriptome analysis, we identified critical genes involved in C and N metabolism that had higher expression in XS6. A significant discovery was the high-affinity nitrate transporter 2.7 gene, which showed elevated expression in XS6, suggesting its key role in enhancing NUE. Metabolomics analysis further complemented these findings, revealing a sophisticated alteration of 1252 metabolites under LN stress, highlighting the dynamic interplay between carbon and N metabolism in coping with N scarcity. The integration of transcriptomic and metabolomic data underscored the crucial role of trehalose in mitigating N deficiency and enhancing NUE. This study provides novel insights into the molecular mechanisms governing NUE in potatoes, offering valuable perspectives for molecular breeding to enhance NUE in potatoes and potentially other crops.

Physiological response to low-nitrogen stress and comprehensive evaluation in four rice varieties

Physiological response to low-nitrogen stress and comprehensive evaluation in four rice varieties

BjuB05.GS1.4 promotes nitrogen assimilation and participates in the domestication of shoot NUE in Brassica juncea

Elucidating crops' physiological and molecular mechanisms to adapt to low nitrogen environment and promoting nitrogen transfer from senescent leaves to new leaves is crucial in improving Brassica's nitrogen use efficiency (NUE). Glutamine synthetase (GS), a vital gene that helps plants to reassimilate ammonium released from protein degradation in leaves, was the focus of our research. In this study, we identified high (H141) and low NUE genotype (L65) genotypes of Brassica juncea with different responses to low-nitrogen stress. We observed that H141 has a lower nitrate content but higher ammonium and free amino acid contents as well as higher nitrate reductase and GS activities in the shoots. These physiological indicators are responsible for the high NUE of H141. Whole-genome resequencing data revealed that 5,880 genes associated with NUE are polymorphic between H141 and L65. These genes participate in amino acid, carbohydrate, and energy metabolic pathways. Haplotype analysis revealed two haplotypes for BjuB05.GS1.4. Hap1 and Hap2 have multiple single nucleotide polymorphisms or insertions/deletions in the regulatory regions of 5′ and 3′ untranslated regions and introns. Furthermore, the shoot NUE of Hap1 is significantly lower than that of Hap2. The two haplotypes of BjuB05.GS1.4 led to differences in the shoot NUEs of different genetic populations of mustard and are associated with the local soil nitrogen content, suggesting that they might help mustard to adapt to different geographies. In conclusion, the results of our study shed light on the physiological and molecular mechanisms underlying different mustard NUE genotypes and demonstrate the enormous potential of NUE breeding in B.juncea.

Transcriptomic Analysis of the Molecular Mechanism Potential of Grafting-Enhancing the Ability of Oriental Melon to Tolerate Low-Nitrogen Stress.

Nitrogen is the primary nutrient for plants. Low nitrogen generally affects plant growth and fruit quality. Melon, as an economic crop, is highly dependent on nitrogen. However, the response mechanism of its self-rooted and grafted seedlings to low-nitrogen stress has not been reported previously. Therefore, in this study, we analyzed the transcriptional differences between self-rooted and grafted seedlings under low-nitrogen stress using fluorescence characterization and RNA-Seq analysis. It was shown that low-nitrogen stress significantly inhibited the fluorescence characteristics of melon self-rooted seedlings. Analysis of differentially expressed genes showed that the synthesis of genes related to hormone signaling, such as auxin and brassinolide, was delayed under low-nitrogen stress. Oxidative stress response, involved in carbon and nitrogen metabolism, and secondary metabolite-related differentially expressed genes (DEGs) were significantly down-regulated. It can be seen that low-nitrogen stress causes changes in many hormonal signals in plants, and grafting can alleviate the damage caused by low-nitrogen stress on plants, ameliorate the adverse effects of nitrogen stress on plants, and help them better cope with environmental stresses.

Integrated morphological, physiological and transcriptomic analyses reveal the responses of Toona sinensis seedlings to low-nitrogen stress

Nitrogen is one of the most essential elements for plant growth and development. In this study, the growth, physiology, and transcriptome of Toona sinensis (A. Juss) Roem seedlings were compared between low-nitrogen (LN) and normal-nitrogen (NN) conditions. These results indicate that LN stress adversely influences T. sinensis seedling growth. The activities of key enzymes related to nitrogen assimilation and phytohormone contents were altered by LN stress. A total of 2828 differentially expressed genes (DEGs) in roots and 1547 in leaves were identified between the LN and NN treatments. A differential enrichment analysis of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways indicated that nitrogen and sugar metabolism, flavonoid biosynthesis, plant hormone signal transduction, and ABC transporters, were strongly affected by LN stress. In summary, this research provides information for further understanding the response of T. sinensis to LN stress.

Establishment of a Comprehensive Evaluation System for Low Nitrogen and Screening of Nitrogen-Efficient Germplasm in Peanut

Screening for nitrogen (N)-efficient germplasm to achieve high yield and high N efficiency is an important strategy to enhance the sustainability of modern agriculture. In this study, 127 peanut (Arachis hypogaea L.) germplasm resources were comprehensively evaluated by seedling hydroponics and field. At the seedling stage, with the range of low-nitrogen screening concentrations gradually narrowed through a comprehensive membership function analysis, standard normal distribution test, and variance analysis, we found that 0.15 mM N for 24 days could be the optimal condition for evaluating the N efficiency of peanuts. Through principal component analysis and correlation analysis, dry matter weight, root/shoot ratio, N content, N accumulation, N-use efficiency, and N use index were considered to be the N efficiency parameters, and a regression mathematical model was established accordingly. In the field, peanut genotypes that differ in resistance to low-nitrogen stress were evaluated by a yield nitrogen efficiency index under normal nitrogen and no nitrogen applications to verify the results at the seedling stage. Based on the multiple phenotypic analysis, N-efficient and N-inefficient peanut genotypes among germplasm were screened, and a comprehensive evaluation system was established to provide the theoretical basis for peanut breeding and cultivation techniques.

Grass-Endophyte Interactions and Their Associated Alkaloids as a Potential Management Strategy for Plant Parasitic Nematodes.

Claviceptaceous endophytic fungi in the genus Epichloë mostly form a symbiotic relationship with cool-season grasses. Epichloë spp. are capable of producing bioactive alkaloids such as peramines, lolines, ergot alkaloids, and indole-diterpenes, which protect the host plant from herbivory by animals, insects, and nematodes. The host also benefits from enhanced tolerance to abiotic stresses, such as salt, drought, waterlogging, cold, heavy metals, and low nitrogen stress. The bioactive alkaloids produced can have both direct and indirect effects towards plant parasitic nematodes. Direct interaction with nematodes' motile stages can cause paralysis (nematostatic effect) or death (nematicidal effect). Indirectly, the metabolites may induce host immunity which inhibits feeding and subsequent nematode development. This review highlights the different mechanisms through which this interaction and the metabolites produced have been explored in the suppression of plant parasitic nematodes and also how the specific interactions between different grass genotypes and endophyte strains result in variable suppression of different nematode species. An understanding of the different grass-endophyte interactions and their successes and failures in suppressing various nematode species is essential to enable the proper selection of grass-endophyte combinations to identify the alkaloids produced, concentrations required, and determine which nematodes are sensitive to which specific alkaloids.

Maize Autophagy-Related Protein ZmATG3 Confers Tolerance to Multiple Abiotic Stresses.

Abiotic stresses pose a major increasing problem for the cultivation of maize. Autophagy plays a vital role in recycling and re-utilizing nutrients and adapting to stress. However, the role of autophagy in the response to abiotic stress in maize has not yet been investigated. Here, ZmATG3, which is essential for ATG8-PE conjugation, was isolated from the maize inbred line B73. The ATG3 sequence was conserved, including the C-terminal domains with HPC and FLKF motifs and the catalytic domain in different species. The promoter of the ZmATG3 gene contained a number of elements involved in responses to environmental stresses or hormones. Heterologous expression of ZmATG3 in yeast promoted the growth of strain under salt, mannitol, and low-nitrogen stress. The expression of ZmATG3 could be altered by various types of abiotic stress (200 mM NaCl, 200 mM mannitol, low N) and exogenous hormones (500 µM ABA). GUS staining analysis of ZmATG3-GUS transgenic Arabidopsis revealed that GUS gene activity increased after abiotic treatment. ZmATG3-overexpressing Arabidopsis plants had higher osmotic and salinity stress tolerance than wild-type plants. Overexpression of ZmATG3 up-regulated the expression of other AtATGs (AtATG3, AtATG5, and AtATG8b) under NaCl, mannitol and LN stress. These findings demonstrate that overexpression of ZmATG3 can improve tolerance to multiple abiotic stresses.

Genetic trends in the Zimbabwe's national maize breeding program over two decades.

Monitoring genetic gains within breeding programs is a critical component for continuous improvement. While several national breeding programs in Africa have assessed genetic gain using era studies, this study is the first to use two decades of historical data to estimate genetic trends within a national breeding program. The objective of this study was to assess genetic trends within the final two stages of Zimbabwe's Department of Research & Specialist Services maize breeding pipeline between 2002 and 2021. Data from 107 intermediate and 162 advanced variety trials, comprising of 716 and 398 entries, respectively, was analyzed. Trials were conducted under optimal, managed drought stress, low nitrogen stress, low pH, random stress, and disease pressure (maize streak virus (MSV), grey leaf spot (GLS), and turcicum leaf blight under artificial inoculation. There were positive and significant genetic gains for grain yield across management conditions (28-35 kg ha-1 yr-1), under high-yield potential environments (17-61 kg ha-1 yr-1), and under low-yield potential environments (0-16 kg ha-1 yr-1). No significant changes were observed in plant and ear height over the study period. Stalk and root lodging, as well as susceptibility to MSV and GLS, significantly decreased over the study period. New breeding technologies need to be incorporated into the program to further increase the rate of genetic gain in the maize breeding programs and to effectively meet future needs.

Regulation of nitrogen metabolism by COE2 under low sulfur stress in Arabidopsis

The interplay between nitrogen and sulfur assimilation synergistically supports and sustains plant growth and development, operating in tandem to ensure coordinated and optimal outcomes. Previously, we characterized Arabidopsis CHLOROPHYLL A/B-BINDING (CAB) overexpression 2 (COE2) mutant, which has a mutation in the NITRIC OXIDE-ASSOCIATED (NOA1) gene and exhibits deficiency in root growth under low nitrogen (LN) stress. This study found that the growth suppression in roots and shoots in coe2 correlates with decreased sensitivity to low sulfur stress treatment compared to the wild-type. Therefore, we examined the regulatory role of COE2 in nitrogen and sulfur interaction by assessing the expression of nitrogen metabolism-related genes in coe2 seedlings under low sulfur stress. Despite the notable upregulation of nitrate reductase genes (NIA1 and NIA2), there was a considerable reduction in nitrogen uptake and utilization, resulting in a substantial growth penalty. Moreover, the elevated expression of miR396 perhaps complemented growth stunting by selectively targeting and curtailing the expression levels of GROWTH REGULATING FACTOR 2 (GRF2), GRF4, and GRF9. This study underscores the vital role of COE2-mediated nitrogen signaling in facilitating seedling growth under sulfur deficiency stress.

Identification and Expression Analysis of the BTB/POZ Gene Family in Solanum tuberosum

The BTB/POZ (broad-complex, tramtrack, and bric-a-brac) family of proteins is widespread in plants and animals and plays important roles in growth, development, metabolism, and environmental responses. There are few reports on BTB family genes in potato. In this study, 34 sequences containing conserved BTB domains were obtained from the potato gene database, and the phylogenetic, physical, and chemical properties, gene structure, conserved motif, domain, and chromosomal localization of the potato BTB protein family were analyzed via bioinformatics methods. In addition, we used qRT-PCR to detect 12 selected StBTB genes. The results confirmed that these genes are involved in cold, ABA, salt, hydrogen peroxide (H2O2), drought, and low-nitrogen stress, which is highly important for elucidating BTB family members and studying stress response and tolerance mechanisms. This study provides a theoretical basis for the study of the function and expression of potato BTB and lays a solid foundation for further understanding the molecular mechanism of the potato BTB gene under various environmental stresses.

Overexpression of CBL-Interacting Protein Kinases 23 Improves Tolerance to Low-Nitrogen Stress in Potato Plants

CBL-interacting protein kinases (CIPKs) play important regulatory roles in plant growth development and abiotic stress tolerance. However, the biological roles of these genes in response to low-nitrate (LN) stress in potato plants have not been determined. Here, we reported that StCIPK23 was expressed mainly in roots and leaves. StCIPK23 was located mainly in the cell membrane, nucleus, and cytoplasm. Further research suggested that, compared with wild-type (WT) plants, StCIPK23-overexpressing plants were taller and had significantly greater nitrate and ammonium nitrogen contents under LN stress. StCIPK23 overexpression can increase StAT, StNRT2.1, StNR, StGS1-3, and StGOGAT expression levels in StCIPK23 transgenic seedlings compared to those in WT plants under LN stress. The results of yeast two-hybrid and luciferase complementation imaging experiments suggested that StCIPK23 could interact with StCBL3. Real-time reverse transcription–PCR revealed the StCIPK23 expression level peaked at 6 h and the StCBL3 expression level peaked at 9 h in the roots under LN stress. In conclusion, we found that StCIPK23 and StCBL3 form a complex to regulate the expression of key genes in the nitrogen metabolism pathway to improve LN tolerance in potato plants.

Transcriptome Analysis of Sesame (Sesamum indicum L.) Reveals the LncRNA and mRNA Regulatory Network Responding to Low Nitrogen Stress.

Nitrogen is one of the important factors restricting the development of sesame planting and industry in China. Cultivating sesame varieties tolerant to low nitrogen is an effective way to solve the problem of crop nitrogen deficiency. To date, the mechanism of low nitrogen tolerance in sesame has not been elucidated at the transcriptional level. In this study, two sesame varieties Zhengzhi HL05 (ZZ, nitrogen efficient) and Burmese prolific (MD, nitrogen inefficient) in low nitrogen were used for RNA-sequencing. A total of 3964 DEGs (differentially expressed genes) and 221 DELs (differentially expressed lncRNAs) were identified in two sesame varieties at 3d and 9d after low nitrogen stress. Among them, 1227 genes related to low nitrogen tolerance are mainly located in amino acid metabolism, starch and sucrose metabolism and secondary metabolism, and participate in the process of transporter activity and antioxidant activity. In addition, a total of 209 pairs of lncRNA-mRNA were detected, including 21 pairs of trans and 188 cis. WGCNA (weighted gene co-expression network analysis) analysis divided the obtained genes into 29 modules; phenotypic association analysis identified three low-nitrogen response modules; through lncRNA-mRNA co-expression network, a number of hub genes and cis/trans-regulatory factors were identified in response to low-nitrogen stress including GS1-2 (glutamine synthetase 1-2), PAL (phenylalanine ammonia-lyase), CHS (chalcone synthase, CHS), CAB21 (chlorophyll a-b binding protein 21) and transcription factors MYB54, MYB88 and NAC75 and so on. As a trans regulator, lncRNA MSTRG.13854.1 affects the expression of some genes related to low nitrogen response by regulating the expression of MYB54, thus responding to low nitrogen stress. Our research is the first to provide a more comprehensive understanding of DEGs involved in the low nitrogen stress of sesame at the transcriptome level. These results may reveal insights into the molecular mechanisms of low nitrogen tolerance in sesame and provide diverse genetic resources involved in low nitrogen tolerance research.

Chloride reduces plant nitrate requirement and alleviates low nitrogen stress symptoms

Chloride (Cl−) is traditionally categorized as an antagonist of nitrate (NO3−) because Cl− hinders plant NO3− transport and accumulation. However, we have recently defined Cl− as a beneficial macronutrient for higher plants, due to specific functions that lead to more efficient use of water, nitrogen (N) and CO2 under optimal N and water supply. When accumulated in leaves at macronutrient levels, Cl− promotes growth through osmotic, physiological, metabolic, anatomical and cellular changes that improve plant performance under optimal NO3− nutrition. Nitrate over-fertilization in agriculture can adversely affect crop yield and nature, while its deficiency limits plant growth. To study the relationship between Cl− nutrition and NO3− availability, we have characterized different physiological responses such as growth and yield, N-use efficiency, water status, photosynthesis, leaf anatomy, pigments and antioxidants in tomato plants treated with or without 5 mM Cl− salts and increasing NO3− treatments (3–15 mM). First, we have demonstrated that 5 mM Cl− application can reduce the use of NO3− in the nutrient solution by up to half without detriment to plant growth and yield in tomato and other horticultural plants. Second, Cl− application reduced stress symptoms and improved plant growth under low-NO3− conditions. The Cl−-dependent resistance to low-N stress resulted from: more efficient use of the available NO3−; improved plant osmotic and water status regulation; improved stomatal conductance and photosynthetic rate; and better antioxidant response. We proposed that beneficial Cl− levels increase the crop ability to grow better with lower NO3− requirements and withstand N deficiency, promoting a more sustainable and resilient agriculture.

Emmer wheat (Triticum dicoccum Schuebl.) favours high photosynthetic capacity adaptation to low nitrogen stress.

Although tetraploid wheat has rich genetic variability for cultivar improvement, its physiological mechanisms associated with photosynthetic productivity and resilience under nitrogen (N) deficit stress have not been investigated. In this study, we selected emmer wheat (Kronos, tetraploid), Yangmai 25 (YM25, hexaploid), and Chinese Spring (CS, hexaploid) as materials and investigated the differences in net photosynthetic rate (Pn), carboxylation capacity, electron transfer capacity, photosynthetic product output, and photosynthetic N allocation under normal N (CK) and low N (LN) through hydroponic experiments. Tetraploid emmer wheat (Kronos) had a stronger photosynthetic capacity than hexaploid wheat (YM25, CS) under low N stress, which mainly associated with the higher degree of PSII opening, electron transfer rate, Rubisco content and activity, ATP/ADP ratio, Rubisco activase (Rca) activity and Rubisco activation state, and more leaves N allocation to the photosynthetic apparatus, especially the proportion of N allocation to carboxylation under low N stress. Moreover, Kronos reduced the feedback inhibition of photosynthesis by sucrose accumulation through higher sucrose phosphate synthetase (SPS) activity and triose phosphate utilization rate (VTPU). Overall, Kronos could allocate more N to the photosynthetic components to improve Rubisco content and activity to maintain photosynthetic capacity under low N stress while enhancing triose phosphate output to reduce feedback inhibition of photosynthesis. This study reveals the physiological mechanisms of emmer wheat that maintain the photosynthetic capacity under low N stress, which will provide indispensable germplasm resources for elite low-N-tolerant wheat improvement and breeding.

OsCIPK2 mediated rice root microorganisms and metabolites to improve plant nitrogen uptake

Crop roots are colonized by large numbers of microorganisms, collectively known as the root-microbiome, which modulate plant growth, development and contribute to elemental nutrient uptake. In conditions of nitrogen limitation, the over-expressed Calcineurin B-like interacting protein kinase 2 (OsCIPK2) gene with root-specific promoter (RC) has been shown to enhance growth and nitrogen uptake in rice. Analysis of root-associated bacteria through high-throughput sequencing revealed that OsCIPK2 has a significant impact on the diversity of the root microbial community under low nitrogen stress. The quantification of nifH gene expression demonstrated a significant enhancement in nitrogen-fixing capabilities in the roots of RC transgenetic rice. Synthetic microbial communities (SynCom) consisting of six nitrogen-fixing bacterial strains were observed to be enriched in the roots of RC, leading to a substantial improvement in rice growth and nitrogen uptake in nitrogen-deficient soils. Forty and twenty-three metabolites exhibiting differential abundance were identified in the roots and rhizosphere soils of RC transgenic rice compared to wild-type (WT) rice. These findings suggest that OSCIPK2 plays a role in restructuring the microbial community in the roots through the regulation of metabolite synthesis and secretion. Further experiments involving the exogenous addition of citric acid revealed that an optimal concentration of this compound facilitated the growth of nitrogen-fixing bacteria and substantially augmented their population in the soil, highlighting the importance of citric acid in promoting nitrogen fixation under conditions of low nitrogen availability. These findings suggest that OsCIPK2 plays a role in enhancing nitrogen uptake by rice plants from the soil by influencing the assembly of root microbial communities, thereby offering valuable insights for enhancing nitrogen utilization in rice cultivation.

Overexpression of oilseed rape trehalose-6-phosphate synthesis gene BnaC02.TPS8 confers sensitivity to low nitrogen and high sucrose-induced anthocyanin accumulation in Arabidopsis.

Overexpression of BnaC02.TPS8 increased low N and high sucrose-induced anthocyanin accumulation. Anthocyanin plays a crucial role in safeguarding photosynthetic tissues against high light, UV radiation, and oxidative stress. Their accumulation is triggered by low nitrogen (N) stress and elevated sucrose levels in Arabidopsis. Trehalose-6-phosphate (T6P) serves as a pivotal signaling molecule, sensing sucrose availability, and carbon (C) metabolism. However, the mechanisms governing the regulation of T6P synthase (TPS) genes responsible for anthocyanin accumulation under conditions of low N and high sucrose remain elusive. In a previous study, we demonstrated the positive impact of a cytoplasm-localized class II TPS protein 'BnaC02.TPS8' on photosynthesis and seed yield improvement in Brassica napus. The present research delves into the biological role of BnaC02.TPS8 in response to low N and high sucrose. Ectopic overexpression of BnaC02.TPS8 in Arabidopsis seedlings resulted in elevated shoot T6P levels under N-sufficient conditions, as well as an increased carbon-to-nitrogen (C/N) ratio, sucrose accumulation, and starch storage under low N conditions. Overexpression of BnaC02.TPS8 in Arabidopsis heightened sensitivity to low N stress and high sucrose levels, accompanied by increased anthocyanin accumulation and upregulation of genes involved in flavonoid biosynthesis and regulation. Metabolic profiling revealed increased levels of intermediate products of carbon metabolism, as well as anthocyanin and flavonoid derivatives in BnaC02.TPS8-overexpressing Arabidopsis plants under low N conditions. Furthermore, yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) analyses demonstrated that BnaC02.TPS8 interacts with both BnaC08.TPS9 and BnaA01.TPS10. These findings contribute to our understanding of how TPS8-mediated anthocyanin accumulation is modulated under low N and high sucrose conditions.