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Corn under weed, low nitrogen, and shade stress

ABSTRACT: 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.

ORGANISM(S): Zea mays

PROVIDER: GSE29132 | GEO | 2011/05/09

SECONDARY ACCESSION(S): PRJNA140449

REPOSITORIES: GEO

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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.

Project description:Purpose: This study is designed to identify genes and processes that are differentially regulated in corn when it is grown with or without weeds through the entire critical weed free period (to V8) or when weeds were removed early in the critical weed free period (at V4) and the plants were allowed to recover until V8. Methods: Corn was grown as described above in field plots near Brookings SD in 2007 and 2008 and RNA was extracted from the top-most leaf tips from four plants per treatment plot. Unidirectional cDNA illumina sequencing libraries were constructed for each sample (pooled leaf tips from the given plot), and were sequenced (some samples were paired end sequenced and some were single end sequenced - all 100 bases for PE and SE reads), quality trimmed, and analyzed using the Tuxedo suite of programs for SE reads of the forward read libraries for each sample. Results: We identified a small number of genes that were differentially expressed in both years. More importantly, gene set enrichment analysis of the data determined that weeds, when present through the critical weed free period impacted phytochrome signaling, defense responses, photosynthetic processes, oxidative stress responses, and various hormone signaling processes. When weeds were removed at V4 and the plants allowed to recover until V8, the weeds still imprinted impacts on phytochrome signaling, oxidative stress, and defense responses. Thus, it appears that weeds presence through the early portion of the critical weed free period, even after removal, induced processes that reduce corn growth and yield that lasted at least through V8. Conclusions: This study represents the first investigation of the impact of the lasting effects of weeds during the early critical weed free period on the transcriptome of corn, and provides additional data on the impact of weeds through the critical weed free period that augments and confirms much of what was observed in similar microarray studies.

Project description:Persistence of the invasive perennial weed leafy spurge is mainly attributed to seasonal production of underground adventitious buds (UABs), which undergo well-defined phases of dormancy (para-, endo- and eco-dormancy). These well-defined phases of dormancy also allow UABs of leafy spurge to survive extreme seasonal variations, including dehydration-stress. Consequently, objectives of this study include understanding the effects of dehydration-stress on vegetative reproduction, flowering competence, and transcript profiles at different phases of bud dormancy. The vegetative growth potential of UABs was monitored by removing the aerial portion of dehydration-stressed plants and re-watering the root system. Further, microarray analysis was used to follow transcriptome profiles to identify critical defense- and signaling-pathways at different phases of dormancy in UABs. Surprisingly, only 3 days of dehydration-stress is required to break the endodormant phase in UABs. In leafy spurge, vernalization of endodormant UABs has previously been shown to induce flower competence, while breaking of endodormancy via dehydration-stress did not induce floral induction. Thus, these two environmental treatments open a unique approach to independently dissect molecular mechanisms involved in endodormancy maintenance and floral competence. Bioinformatics analysis of transcriptome data helped to identify models and overlapping pathways. During endodormancy break, LEC1, PHOTOSYSTEM I RC, and brassinosteroids were identified as ooverlapping hubs of up-regulated genes, and DREB1A, CBF2, GPA1, MYC2, BHLH, BZIP, and flavonoids were identified as overlapping hubs of down-regulated genes. Additionally, key genes involved in metabolic activity, chromatin modification, and cross-talk between growth regulators were identified as playing a role during endodormancy maintenance. Plant material, controlled environmental treatments, and vegetative growth: Three-month-old paradormant leafy spurge plants grown in a greenhouse were acclimated for one week, under growth chamber conditions, prior to being subjected to a ramp-down in temperature (27 °C → 10 °C) and photoperiod (16 h → 8 h light) for 12 weeks to induce endodormancy, as previously established (Doğramacı et al. 2010; Foley et al. 2009). Endodormancy status was confirmed by comparing vegetative growth rates of plants with and without a ramp-down treatment. To study the effects of dehydration-stress on vegetative growth from UABs, water was withheld from endodormant plants up to 21 days. After dehydration for 0, 1-, 3-, 7-, 14-, and 21-days, the aerial portion of the plants were decapitated at the soil surface and vegetative growth and floral competence of UABs were monitored under growth-conducive conditions by re-watering the root system. Vegetative shoot growth from six plants was recorded weekly for four weeks, and results of four replications were analyzed using SAS 9.2 (SAS Institute, Cary, NC, 2008) software as described by Doğramacı et al. (2010). Microarray analysis: At the end of each treatment, crown buds were collected, and RNA extraction, cDNA synthesis, fluorescent labeling, microarray hybridization using ~23K element arrays, and spot intensity analyses were performed as previously described by Doğramacı et al. (2010). Based on unexpected vegetative growth results obtained from this study, only microarray data obtained from 0-, 1-, and 3-day dehydration-stressed endodormant UABs, which were compared with microarray data for endodormant, and flowering competent ecodormant UABs from our previous study (Doğramacı et al. 2010; GSE19217), were used for bioinformatics analyses. However, to merge the datasets from these two separate experiments, T-tests were first performed on microarray data obtained from endodormant UABs from each experiment, and differentially-expressed genes (p<0.005) were removed from the dataset (~5% of the spots). After removing the outliers, the two endodormant transcriptome data sets were grouped together and used as the baseline control for further ANOVA, T-tests and other analyses. Array normalization, statistical analyses and clustering of the dataset and Venn diagram generation were done using GeneMaths XT 5.1 software as previously described by Doğramacı et al. (2010).

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Corn under weed, low nitrogen, and shade stress

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