Project description:Nitrate (NO3-) is crucial for optimal plant growth and development and often limits crop productivity at the low availability. In comparison with model plant Arabidopsis, the molecular mechanisms underlying NO3- acquisition and utilization remain largely unclear in maize. In particular, only a few genes have been exploited to improve nitrogen use efficiency (NUE). Here, we demonstrated that NO3--inducible ZmNRT1.1B (ZmNPF6.6) positively regulated NO3--dependent growth and NUE in maize. We showed that the tandem duplicated proteoform ZmNRT1.1C is irrelevant to maize seedling growth under nitrate supply, however, loss-of-function of ZmNRT1.1B significantly weakened plant growth under adequate NO3- supply in both hydroponic and field conditions. 15N-labeled NO3- absorption assay indicated that ZmNRT1.1B mediated high-affinity NO3--transport and root-to-shoot NO3- translocation. Furthermore, upon NO3- supply, ZmNRT1.1B promotes cytoplasmic-to-nuclear shuttling of ZmNLP3.1 (ZmNLP8), which co-regulates the expression of genes involved in NO3- response, cytokinin biosynthesis and carbon metabolism. Remarkably, overexpression of ZmNRT1.1B in modern maize hybrids improved grain yield under nitrogen (N) limiting fields. Taken together, our study revealed a crucial role of ZmNRT1.1B in high-affinity NO3- transport and signaling and offers valuable genetic resource for breeding nitrogen use efficient high-yield cultivars.
Project description:gnp3-b4_nitrogen_starvation - nitrogen starvation and re-supply - What are the transcriptomic short- and long-term plant responses to nitrogen starvation and nitrogen re-supply? - WS Arabidopsis ecotype were grown on 6mM nitrate as sole nitrogen source during 35 days under short days . At T0, plants were then starved for nitrate for 10 days and root and shoot samples were harvested separately 2 and 10 days after treatment (T2, T10). Then, nitrate (6 mM) was re-supplied for 1 and 24 hours (T+1, T+24). Keywords: time course
Project description:The metabolic response of maize source leaves to low nitrogen supply was analyzed in maize seedlings by parallel measurements of transcriptome and metabolome profiling. Inbred lines A188 and B73 were cultivated under controlled growth chamber conditions and supplied with either sufficient (15mM) or limiting (0.15mM) nitrate supply. Leaf lamina material was harvested at day 20 and day 30 after germination with the fifth and sixth leaf representing the main source leaf respectively. Four replicates were collecetd from individual plants for each combination of genotype, growth stage and nitrogen treatment. The leaf material was frozen, homogenised and aliquoted for transcriptome and metabolome analysis. The molecular data was further supplemented by phenotypic characterisation of the maize seedlings under investigation. Limited availability of nitrogen caused strong shifts in the metabolite profile of leaves. The transcriptome was less affected by the nitrogen stress but showed strong genotype and age dependent patterns. Nitrogen starvation initiated the selective down-regulation of processes involved in nitrate reduction and amino acid assimilation; ammonium assimilation related transcripts on the other hand were not influenced. Carbon assimilation related transcripts were characterized by high transcriptional coordination and general down-regulation under low nitrogen conditions. Nitrogen deprivation caused a slight accumulation of starch, but also directed increased amounts of carbohydrates into the cell wall and secondary metabolites. The decrease in N availability also resulted in accumulation of phosphate and by strong down-regulation of genes usually involved in phosphate starvation response, underlining the great importance of phosphate homeostasis control under stress conditions.
Project description:The metabolic response of maize source leaves to low nitrogen supply was analyzed in maize seedlings by parallel measurements of transcriptome and metabolome profiling. Inbred lines A188 and B73 were cultivated under controlled growth chamber conditions and supplied with either sufficient (15mM) or limiting (0.15mM) nitrate supply. Leaf lamina material was harvested at day 20 and day 30 after germination with the fifth and sixth leaf representing the main source leaf respectively. Four replicates were collecetd from individual plants for each combination of genotype, growth stage and nitrogen treatment. The leaf material was frozen, homogenised and aliquoted for transcriptome and metabolome analysis. The molecular data was further supplemented by phenotypic characterisation of the maize seedlings under investigation. Limited availability of nitrogen caused strong shifts in the metabolite profile of leaves. The transcriptome was less affected by the nitrogen stress but showed strong genotype and age dependent patterns. Nitrogen starvation initiated the selective down-regulation of processes involved in nitrate reduction and amino acid assimilation; ammonium assimilation related transcripts on the other hand were not influenced. Carbon assimilation related transcripts were characterized by high transcriptional coordination and general down-regulation under low nitrogen conditions. Nitrogen deprivation caused a slight accumulation of starch, but also directed increased amounts of carbohydrates into the cell wall and secondary metabolites. The decrease in N availability also resulted in accumulation of phosphate and by strong down-regulation of genes usually involved in phosphate starvation response, underlining the great importance of phosphate homeostasis control under stress conditions. Maize inbred lines A188 and B73 were cultivated in pots containing nutrient poor peat soil under the controlled conditions of a growth chamber. The plants were fertilized with modified Hoagland solutions containing either 15mM (high N) or 0.15mM nitrate (low N). Source leaf lamina were harvested at day 20 and day 30 after start of germination for parallel analysis of transcriptome and metabolome profiles. The molecular data is further supplemented by phenotypic characterization of the maize seedlings under investigation.
Project description:In comparison with provision of either ammonium or nitrate alone, simultaneously supplying both forms of N results in superior growth and yield for the majority of plants including rice. Using a rice 22K oligo-array, we performed transcriptome analysis to identify genes of rice (Oryza sativa L. ssp. japonica) responsive to change of N-supply forms and N-starvation. Using the supply of ammonium nitrate (one to one molar ratio) as control, the total number of root genes that were equal or more than two fold up- or down- regulated was 445, 324, and 781 by upon supply of either ammonium or nitrate or continuous N starvation, respectively for 96 h. In the shoot the equivalent numbers were much smaller only 32, 58, and 165, respectively. Clustering of the rice genes associated with different environmental stresses revealed substantial organ specificity of the root and shoot to N starvation, and also to the N supply form. Genes encoding transporters for ammonium and nitrate, nitrate reductase, glutamate dehydrogenase, and aspartate amino transferase, showed great response to change of the N supply form, especially to N starvation. Some of the genes involved in chlorophyll metabolism, carbon fixation and assimilation, were enhanced by ammonium supply only, but significantly suppressed by N-starvation. In the shoot there was increased expression of more general stress genes under nitrate when compared to ammonium nutrition. In the root the reverse situation was true with more apparent stress under ammonium nutrition. The microarray approach has revealed new levels of complexity in the response of rice to the form of N supply. Keywords: Rice; root; shoot; nitrogen starvation; nitrogen form; ammonium; nitrate; gene expression
Project description:ra05-09_urea - urea - What are the transcriptomic plant responses to urea nitrogen supply ? - Columbia Arabidopsis ecotype were grown hydroponically on 0.5 mM NH4NO3 as sole nitrogen source during 35 days under short days. Plants were then placed on 3 nutrient solutions supplemented, either with 1 mM NH4NO3, or with 0.5 mM NH4NO3 + 0.5 mM Urea, or with 1 mM Urea. Root and shoot samples were harvested separately 7 days after these different nitrogen treatments Keywords: treated vs untreated comparison
Project description:Herbaspirillum seropedicae is an endophytic bacterium that can fix nitrogen and promote a hormonal imbalance that leads to a plant growth-promoting effect when used as a microbial inoculant. Studies focused on mechanisms of action are crucial for a better understanding of the bacteria-plant interaction and optimization of plant growth-promoting response. The work aims to understand the underlined mechanisms responsible for the early stimulatory growth effects of the H. seropedicae inoculation in maize. To perform it, we combined transcriptomic and proteomic approaches with physiological analysis. The results obtained with the inoculation showed increased root biomass (233 and 253%) and shoot biomass (249 and 264%), respectively, for the fresh and dry mass of maize seedlings and increased green content and development. Omics data analysis for the positive biostimulation phenotype revealed that inoculation increases N-uptake and N-assimilation machinery through differential expressed nitrate transporters and amino acids pathway, as well carbon/nitrogen metabolism integration by the tricarboxylic acid cycle and the polyamines pathway. Additionally, phytohormone levels of root and shoot tissues increased in bacterium-inoculated-maize plants leading to feedback regulation by the ubiquitin-proteasome system. The early biostimulatory effect of H. seropedicae partially results from hormonal imbalance coupled with efficient nutrient uptake-assimilation and a boost in primary anabolic metabolism of carbon-nitrogen integrative pathways.
Project description:The environment plays important role in the interaction between plant hosts and pathogens. The application of chemical fertilizer is a crucial breeding technology to enhance crop yield since last century. As the most abundant fertilizer, nitrogen often increases disease susceptibility for crop plants. The underlying mechanism for nitrogen induced disease susceptibility is elusive. Here we found that nitrogen application activate gibberellin signaling by degradation of SLR1, the repressor protein in gibberellin signaling, which result in simultaneously promoting plant growth and disease susceptibility. SLR1, physically interacts with OsNPR1 and consequently facilitate OsNPR1 mediated defense responses. Transcriptome analysis showed that OsNPR1-SLR1 module plays a vital role in transcriptional reprogramming for both disease resistance and plant growth. Increase of SLR1 protein level in gibberellin deficient rice plants neutralizes disease susceptibility but sacrifice yield enhancement under high nitrogen supply. Mutation in SD1, encoding OsGA2ox2, produced more grains than WT,and maintains disease resistance under high nitrogen supply. Taken together, our work reveals the molecular mechanism underlying nitrogen-induced disease susceptibility, and demonstrates that the application of sd1 rice varieties prevent the tradeoff between disease susceptibility and yield increase under high nitrogen supply.
Project description:Development of crop varieties with high nitrogen use efficiency (NUE) is crucial for minimizing N loss, reducing environmental pollution and decreasing input cost. Maize is one of the most important crops cultivated worldwide and its productivity is closely linked to the amount of fertilizer used. A survey of the transcriptomes of shoot and root tissues of a maize hybrid line and its two parental inbred lines grown under sufficient and limiting N conditions by mRNA-Seq has been conducted to have a better understanding of how different maize genotypes respond to N limitation.
Project description:Plants face temporal and spatial variation in nitrogen (N) availability. This includes heterogeneity in soil nitrate (NO3-) content. To face these constraints, plants modify their gene expression and physiological processes to optimize N acquisition. This plasticity relies on a complex long-distance root-shoot-root signaling network that remains poorly understood. We previously showed that cytokinin (CK) biosynthesis is required to trigger systemic N signaling. Here, we performed split-root experiments and used a combination of CK-related mutant analyses, hormone profiling, transcriptomic analysis, NO3- uptake assays, and root growth measurements to gain insight into systemic N signaling in Arabidopsis thaliana. By comparing wild-type plants and mutants affected in CK biosynthesis and ABCG14-dependent root-to-shoot translocation of CK, we revealed an important role for active trans-Zeatin (tZ) in systemic N signaling. Both rapid sentinel gene regulation and long-term functional acclimation to heterogeneous NO3- supply, including NO3- transport and root growth regulation, are likely mediated by the integration of tZ content in shoots. Furthermore, shoot transcriptome profiling revealed that glutamate/glutamine metabolism is likely a target of tZ root-to-shoot translocation, prompting an interesting hypothesis regarding shoot-to-root communication. Finally, this study highlights tZ-independent pathways regulating gene expression in shoots as well as NO3- uptake activity in response to total N-deprivation. We used microarrays to detail transcriptional reprogramming occurring in shoots in response to heterogeneous nitrate supply compared to homogeneous nitrate supply in wild-type Arabidopsis thaliana plants and in two mutants affected in cytokinin biosynthesis and transport.