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:Intercropping is a vital technology in resource-limited agricultural systems with low inputs. Peanut/maize intercropping enhances iron (Fe) nutrition in calcareous soil. Proteomic studies of the differences in peanut leaves, maize leaves and maize roots between intercropping and monocropping systems indicated that peanut/maize intercropping not only improves Fe availability in the rhizosphere but also influences the levels of proteins related to carbon and nitrogen metabolism. Moreover, intercropping may enhance stress resistance in the peanut plant (Xiong et al. 2013b). Although the mechanism and molecular ecological significance of peanut/maize intercropping have been investigated, little is known about the genes and/or gene products in peanut and maize roots that mediate the benefits of intercropping. In the present study, we investigated the transcriptomes of maize roots grown in intercropping and monocropping systems by microarray analysis. The results enabled exploration differentially expressed genes in intercropped maize. Peanut (Arachis hypogaea L. cv. Luhua14) and maize (Zea mays L. cv. Nongda108) seeds were grown in calcareous sandy soil in a greenhouse. The soil was enhanced with basal fertilizers [composition (mg·kg−1 soil): N, 100 (Ca (NO3)2·4H2O); P, 150 (KH2PO4); K, 100 (KCl); Mg, 50 (MgSO4·7H2O); Cu, 5 (CuSO4·5H2O); and Zn, 5 (ZnSO4·7H2O)]. The experiment consisted of three cropping treatments: peanut monocropping, maize monocropping and intercropping of peanut and maize. After germination of peanut for 10 days, maize was sown. Maize samples were harvested after 63 days of growth of peanut plants based on the degree of Fe chlorosis in the leaves of monocropped peanut. The leaves of monocropped peanut plants exhibited symptoms of Fe-deficiency chlorosis at 63 days, while the leaves of peanut plants intercropped with maize maintained a green color.
Project description:Nitrogen availability in the soil is a major determinant of crop yield. While the application of fertilizer can substantially increase the yield on poor soils, it also causes nitrate pollution of water resources and high costs for farmers. Increasing the nitrogen use efficiency in crop plants is a necessary step to implement low input agricultural systems. We exploited the genetic diversity present in the world-wide Arabidopsis thaliana population to study adaptive growth patterns and changes in gene expression associated with chronic low nitrate stress, with the aim to identify biomarkers associated with good plant performance under low nitrate availability. Transcription and epigenetic factors were identified as important players in the adaptatiion to limited nitrogen in a global gene expression analysis using the Affymetrix ATH1 chip.
Project description:Intercropping is a sustainable agricultural practice widely used around the world for enhancing resource use efficiency. However, short crops often grow in shade condition underneath the canopy of tall crops. Soybean is one of the most important oil crops and usually is planted in intercropping patterns. However, little is known about the acclimation responses of soybean leaves to shade in intercropping condition at the transcriptome level.
Project description:Algal biofuel production requires an input of synthetic nitrogen fertilizer. Fertilizer synthesized via the Haber-Bosch process produces CO2 as a waste by-product and represents a substantial financial and energy investment. Reliance on synthetic fertilizer attenuates the environmental significance and economic viability of algae production systems. To lower fertilizer input, the waste streams of algal production systems can be recycled to provide alternative sources of nitrogen such as amino acids to the algae. The halophytic green alga Dunaliella viridis can use ammonium (NH4+) derived from the abiotic degradation of amino acids, and previously, supplementation of NH4+ from glutamine (GLN) degradation was shown to support acceptable levels of growth and increased neutral lipid production compared to nitrate. To understand the effect of glutamine-released NH4+ on algae growth and physiology, metabolite levels, growth parameters, and transcript profiles of D. viridis cultures were observed in a time course after transition from media containing nitrate as a sole N source to medium containing GLN, glutamate (GLU), or a N-depleted medium. Growth parameters were similar between GLN (NH4+) and nitrate supplemented cultures, however, metabolite data showed that the GLN supplemented cultures (NH4+) more closely resembled cultures under nitrogen starvation (N-depleted and GLU supplementation). Neutral lipid accumulation was the same in nitrate and glutamine-derived NH4+ cultures. However, glutamine-derived NH4+ caused a transcriptional response in the immediate hours after inoculation of the culture. The strong initial response of cultures to NH4+ changed over the course of days to closely resemble that of nitrogen starvation. These observations suggest that release of NH4+ from glutamine was sufficient to maintain growth, but not high enough to trigger a cell transition to a nitrogen replete state. Comparative transcript profiling of the nitrogen-starved and nitrate-supplied cultures show an overall downregulation of fatty acid synthesis and a shift to starch synthesis and accumulation. The results indicate that a continuous, amino acid derived slow release of NH4+ to algae cultures could reduce the amount of synthetic nitrogen needed for growth, but optimization is needed to balance nitrogen starvation and cell division.
Project description:Nitrogen is one of the essential elements for plant growth. NH4+ and NO3- are two major forms of absorbing element N for higher plants. In this study we found that the growth of Panax notoginseng is inhibited when only adding ammonium nitrogen fertilizer, and adding nitrate fertilizer can alleviate the toxicity caused by ammonium. We use RNA-seq to identify genes that are related to the alleviated phenotypes after introducing NO3- to Panax notoginseng roots under NH4+ stresses. Twelve RNA-seq profiles in four sample groups, i.e., control, samples treated with NH4+, samples treated with NO3- only, and treated with both NH4+ and NO3- were obtained and analyzed to identify deregulated genes in samples with different treatments. ACLA-3 gene is downregulated in NH4+ treated samples, but is upregulated in samples treated with NO3- and with both NH4+ and NO3-, which is further validated in another set of samples using qRT-PCR. Our results suggest that unbalanced metabolism of nitrogen and nitrogen is the main cause of ammonium poisoning in roots of Panax notoginseng, and NO3- may significantly upregulate the activity of ACLA-3 which subsequently enhances the citrate cycle and many other metabolic pathways in Panax notoginseng root. These potentially increase the integrity of the Panax notoginseng roots. Our results suggest that introducing NO3- fertilizer is an effective means to prevent the occurrence of toxic ammonium in Panax notoginseng root.