Project description:Soil humic substances are known to positively influence plant growth and nutrition. In particular, low-molecular fractions have been shown to increase NO3- uptake and PM H+-ATPase activity and alter expression of related genes. Changes in maize root transcriptome due to treatment with nitrate (NO3-), Water-Extractable Humic Substances (WEHS) and NO3-+WEHS were analyzed.
Project description:Maize (Zea mays L.) was hydroponically grown for 14 days and then stressed with hypoxia. Maize roots were sampled after 24 hours and analyzed by mass spectrometry.
Project description:The goal of this work was to investigate the influence of low red to far-red (R:FR) signals generated by a biological weedy and an artificial source of far-red light on the nitrate assimilation pathway in maize. In the absence of direct resource competition, far-red light reflected from neighboring weeds compromises light quality (red to far-red ratio; R/FR) and causes a wide range of morphological and physiological responses at early growth stages of crop plants. This study has investigated the effects of low R/FR light signals on nitrate assimilation in maize seedlings. The transcript levels of genes, metabolites, and activities of enzyme in the nitrate assimilation pathway under a biological and a simulated low R:FR light environment were compared with a high R:FR control environment. Low R:FR signals stimulated nitrate accumulation in maize leaves, which did not appear to result from the upregulation of nitrate transporter genes. A significant reduction in ferredoxin-dependent glutamine:2-oxoglutarate aminotransferase activity appears to play a major role in nitrate accumulation under low R:FR light environments, while activities of other enzymes of the nitrate assimilation pathway remain unchanged.
Project description:Plant nutrition takes advantage by the simultaneous presence of more N forms in the rhizosphere. In the last decades the interplay between ammonium and nitrate acquisition systems in roots has been deeply investigated. Although widely used as fertilizers, the occurrence of cross connection between urea and ammonium nutrition has been scarcely studied in plants, especially at molecular level. In a recent paper we provided evidence that maize plants fed with urea and ammonium mix showed a better N-uptake efficiency than plants fed with ammonium or urea alone. To elucidate the molecular mechanism underlying this response, transcriptomic and metabolomic changes occurring in maize plants were investigated. Transcriptomic analyses indicated that several transporters and enzymes involved in N-nutrition were found upregulated by all three N-treatments (AMT1.3, NRT1.1, NRT2.1, GS1, GOGAT, GDH), confirming that urea is a direct source of N for plants. Depending on N-form available in nutrient solution a peculiar response at transcriptomic and metabolomic level was observed, especially after 24 hours of treatment. In comparison to one single N-form, urea and ammonium mix induced a prompt assimilation of N, characterized by an overaccumulation of main amino acids in shoots, and an upregulation of ZmAMT1.1. Moreover even a peculiar modulation of aquaporins, carbonic anydrases, glutamine synthetase, amino aspartate, as well as the glycolysis-TCA cycle was induced in roots by urea and ammonium mix. Depending on N-form available in the external media, even changes in phytohormone’s composition were observed in maize (CKs, ABA, JA); in particular, already after 24 hours of treatment, urea induced the accumulation of trans-zeatin in shoots. Through a multiomics approach, we provide for the first time molecular characterization of maize response to urea and ammonium nutrition. This study paves the way to formulate guidelines for the optimization of N fertilization of crops to improve the N use efficiency in plants and therefore limit N losses in the environment.
Project description:Arable soils are extremely heterogeneous in spatial nutrient distribution. It is well documented that lateral roots (LRs) proliferate in nitrate-rich patch. Yet less information is available as to which genes are involved in this process, in particular in cereals. To understand the molecular mechanism for local nitrate induced LR growth in maize (Zea mays L.), we analyzed the gene expression profiling in maize root in early response (1 hour) to local nitrate stimulation by using Maize Oligonucleotide Array (http://www.maizearray.org) and a split-root system. Selected differentially expressed genes were further confirmed by semi-quantitative RT-PCR. The results showed that reception and/or transduction of local NO3- signal involve some important protein kinases and protein phosphatases (histidine kinases, serine/threonine kinases, protein phosphatase 2A etc.) and transcription factors (F-box, Zinc finger, Myb and bZIP transcription factors and response regulator). Increasing expression of genes encoding auxin response factor 7b, ethylene receptor, and cytokinin oxidase suggests strong interaction among hormonal pathways and local NO3- signaling pathways. Genes involving NO3- uptake and assimilation (NRT2.1, NR, etc.), sugar transport (a sugar transporter) and utilization (a sucrose synthase) were enhanced in the N-fed root. Furthermore, local NO3- induces rapid expression of genes related to cell division and expansion such as alpha-expansin, celluose synthase, kinesin, plasma membrane and tonoplast aquaporins. Based on the differentially expressed genes, a putative model which combines both the 'NO3- signal' and 'metabolic sink' theories is proposed to explain the molecular mechanism controlling local nitrate induced LR elongation in maize.
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:In this study a transcriptomic approach (RNA-sequencing) was utilized to elucidate molecular responses of maize (Zea mays L.) primary roots of the inbred line B73 to water deficit to gain a better understanding of the mechanisms underlying drought tolerance. Kernels of the maize inbred line B73 were germinated in paper rolls soaked with distilled water until seedlings had a primary root length of 2 to 4 cm. For mild and severe water deficit conditions, seedlings were transferred to PEG8000 solution with water potentials of -0.2 MPa and -0.8 MPa, respectively. Water deficit treatment was applied for 6 h and 24 h. Each treatment was performed in four biological replicates each consisting of 10 roots.
Project description:Arable soils are extremely heterogeneous in spatial nutrient distribution. It is well documented that lateral roots (LRs) proliferate in nitrate-rich patch. Yet less information is available as to which genes are involved in this process, in particular in cereals. To understand the molecular mechanism for local nitrate induced LR growth in maize (Zea mays L.), we analyzed the gene expression profiling in maize root in early response (1 hour) to local nitrate stimulation by using Maize Oligonucleotide Array (http://www.maizearray.org) and a split-root system. Selected differentially expressed genes were further confirmed by semi-quantitative RT-PCR. The results showed that reception and/or transduction of local NO3- signal involve some important protein kinases and protein phosphatases (histidine kinases, serine/threonine kinases, protein phosphatase 2A etc.) and transcription factors (F-box, Zinc finger, Myb and bZIP transcription factors and response regulator). Increasing expression of genes encoding auxin response factor 7b, ethylene receptor, and cytokinin oxidase suggests strong interaction among hormonal pathways and local NO3- signaling pathways. Genes involving NO3- uptake and assimilation (NRT2.1, NR, etc.), sugar transport (a sugar transporter) and utilization (a sucrose synthase) were enhanced in the N-fed root. Furthermore, local NO3- induces rapid expression of genes related to cell division and expansion such as alpha-expansin, celluose synthase, kinesin, plasma membrane and tonoplast aquaporins. Based on the differentially expressed genes, a putative model which combines both the 'NO3- signal' and 'metabolic sink' theories is proposed to explain the molecular mechanism controlling local nitrate induced LR elongation in maize. plants were pre-cultured in solution containing 0.5 mmol L-1 NO3- for 6 days and then transferred to N-free solution to grow for another 2 days. Then these plants were transferred to a two-compartment split-root system with only half root supplied with 1.0 mmol L-1 NO3-. Supply of Ca2+ in the N-free half was compensated by adding 1.0 mmol L-1 CaCl2. One hour after the local nitrate treatment, root segments (15cm from root tip to lateral root elongation zone) were sampled for RNA extraction. Two biological replicates were performed for each treatment.
Project description:In this study RNA-sequencing was used to monitor gene expression changes in four tissues (meristematic zone, elongation zone, and cortex and stele of the mature zone) of maize (Zea mays L.) primary roots in response to water deficit to gain a better understanding of the mechanisms underlying drought tolerance.
Project description:It was investigated the changes in protein expression in maize roots in response to treatment with Herbaspirillum seropedicae. To identify maize proteins whose expression levels were altered in the presence of bacteria, a label-free quantitative proteomic approach was used.