Project description:Abiotic stress causes disturbances in the cellular homeostasis. Re-adjustment of balance in carbon, nitrogen and phosphorus metabolism therefore plays a central role in stress adaptation. However, it is currently unknown which parts of the primary cell metabolism follow common patterns under different stress conditions and which represent specific responses. To address these questions, changes in transcriptome, metabolome and ionome were analyzed in maize source leaves from plants suffering low temperature, low nitrogen (N) and low phosphorus (P) stress. The selection of maize as study object provided data directly from an important crop species and the so far underexplored C4 metabolism. Growth retardation was comparable under all tested stress conditions. The only primary metabolic pathway responding similar to all stresses was nitrate assimilation, which was down-regulated. The largest group of commonly regulated transcripts followed the expression pattern: down under low temperature and low N, but up under low P. Several members of this transcript cluster could be connected to P metabolism and correlated negatively to different phosphate concentration in the leaf tissue. Accumulation of starch under low temperature and low N stress, but decrease in starch levels under low under low P conditions indicated that only low P treated leaves suffered carbon starvation. In conclusion, maize employs very different strategies for management of nitrogen and phosphorus metabolism under stress. While nitrate assimilation was regulated depending on demand by growth processes, phosphate concentrations changed depending on availability, thus building up reserves under excess conditions. Carbon and energy metabolism of the C4 maize leaves were particularly sensitive to P starvation. Responses of maize source leaves to low temperature, low nitrogen and low phosphorus conditions were tested in independent single-stress experiments. Seedlings 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 15mM KNO3 and 0.5mM KH2PO4 for control conditions; for low N and low P treatment, the nutrient concentrations were reduced to 0.15mM KNO3 and 0.1mM KH2PO4, respectively. Low temperature treated plants were always supplied with control nutrient solution. Plants from the nitrogen and phosphorus experiment as well as the control temperature plants were exposed to 28Â°C during the day and 20Â°C during the night. Low temperature treatment was limited to the night period and was reduced to 4Â°C for the 10h dark period. Source leaf lamina were harvested at day 20 (low temperature experiment) or day 30 after start of germination (low nitrogen and low phosphorus experiment) for parallel analysis of transcriptome, metabolome and ion profiles. The molecular data is further supplemented by phenotypic characterization of the maize seedlings under investigation.

Project description:This study was designed to identify changes in gene expression when corn was placed under various related stresses including being grown with a competing weed (canola) to the V4 or V8 stage, or when 40% shade cloth was present to the V4 or V8 stage, or under low nitrogen (no added nitrogen fertilizer), or under weed/shade free fertilized control conditions. In all 5 treatments and the control, samples were harvested at V8. Mechanisms underlying early season weed stress on crop growth are not well described. Corn vegetative growth and development, yield, and gene expression response to nitrogen (N), light (40% shade), and weed stresses were compared with the response of nonstressed plants. Vegetative parameters, including leaf area and biomass, were measured from V2 toV12 corn stages. Transcriptome (2008) or quantitative Polymerase Chain Reaction (q PCR) (2008/09) analyses examined differential gene expression in stressed versus nonstressed corn at V8. Vegetative parameters were impacted minimally by N stress although grain yield was 40% lower. Shade, present until V2, reduced biomass and leaf area > 50% at V2 and, at V12, recovering plants remained smaller than nonstressed plants. Grain yields of shade-stressed plants were similar to nonstressed controls, unless shade remained until V8. Growth and yield reductions due to weed stress in 2008 were observed when weeds remained until V6. In 2009, weed stress at V2 reduced vegetative growth, and weed stress until V4 or later reduced yield. Principle component analysis of differentially expressed genes indicated that shade and weed stress had more similar gene expression patterns to each other than to nonstressed or low N stressed tissues. Weed-stressed corn had 630 differentially expressed genes compared with the nonstressed control. Of these genes, 259 differed and 82 were shared with shade-stressed plants. Corn grown in N-stressed conditions shared 252 differentially expressed genes with weed-stressed plants. Ontologies associated with light/photosynthesis, energy conversion, and signaling were down-regulated in response to all three stresses. Although shade and weed stress clustered most tightly together, only three ontologies were shared by these stresses, O-methyltransferase activity (lignification processes), Poly U binding activity (post-transcriptional gene regulation), and stomatal movement. Based on both morphologic and genomic observations, results suggest that shade, N, and weed stresses to corn are regulated by both different and overlapping mechanisms.

Project description:This study was designed to identify changes in gene expression when corn was placed under various related stresses including being grown with a competing weed (canola) to the V4 or V8 stage, or when 40% shade cloth was present to the V4 or V8 stage, or under low nitrogen (no added nitrogen fertilizer), or under weed/shade free fertilized control conditions. In all 5 treatments and the control, samples were harvested at V8. Mechanisms underlying early season weed stress on crop growth are not well described. Corn vegetative growth and development, yield, and gene expression response to nitrogen (N), light (40% shade), and weed stresses were compared with the response of nonstressed plants. Vegetative parameters, including leaf area and biomass, were measured from V2 toV12 corn stages. Transcriptome (2008) or quantitative Polymerase Chain Reaction (q PCR) (2008/09) analyses examined differential gene expression in stressed versus nonstressed corn at V8. Vegetative parameters were impacted minimally by N stress although grain yield was 40% lower. Shade, present until V2, reduced biomass and leaf area > 50% at V2 and, at V12, recovering plants remained smaller than nonstressed plants. Grain yields of shade-stressed plants were similar to nonstressed controls, unless shade remained until V8. Growth and yield reductions due to weed stress in 2008 were observed when weeds remained until V6. In 2009, weed stress at V2 reduced vegetative growth, and weed stress until V4 or later reduced yield. Principle component analysis of differentially expressed genes indicated that shade and weed stress had more similar gene expression patterns to each other than to nonstressed or low N stressed tissues. Weed-stressed corn had 630 differentially expressed genes compared with the nonstressed control. Of these genes, 259 differed and 82 were shared with shade-stressed plants. Corn grown in N-stressed conditions shared 252 differentially expressed genes with weed-stressed plants. Ontologies associated with light/photosynthesis, energy conversion, and signaling were down-regulated in response to all three stresses. Although shade and weed stress clustered most tightly together, only three ontologies were shared by these stresses, O-methyltransferase activity (lignification processes), Poly U binding activity (post-transcriptional gene regulation), and stomatal movement. Based on both morphologic and genomic observations, results suggest that shade, N, and weed stresses to corn are regulated by both different and overlapping mechanisms. three biological replicates for each treatment and the control were collected and the resulting labeled cDNA was hybridized to the 46,000-element maize microarray chip developed by the University of Arizona using their protocol (International Microarray Workshop Handbook, 2009Gardiner et al. 2005). The hybridization scheme was a dual hybridization using a rolling circle balanced dye swap design. Thus we had thre biological replicates for each growth condition amd two technical replicates for each biological sample.

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Low nitrogen stress

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