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:Heterosis, a phenomenon where hybrids exhibit superior performance in various traits such as yield, quality, and resistance compared to their parents, has long been a focus of agricultural research. Although tobacco biomass significantly affects tobacco yield and economic profitability, the underlying reasons for the dominance of tobacco biomass hybrids and their formation remain unclear. To address this, we selected 5 tobacco varieties (lines) with large differences in tobacco biomass as the parents and formulated F1 hybrids to analyze the expression of tobacco biomass heterosis. Our findings demonstrate that tobacco leaf biomass exhibits a clear heterosis advantage. In particular, the hybrid Va116×GDH94 showed strong heterosis, with 76.69% of differentially expressed genes (DEGs) displaying Overdominant expression pattern. Notably, these Overdominant DEGs were significantly enriched in biological processes such as photosynthesis and respiration. During photosynthesis, transgressive up-regulation of Lhc improved light-harvesting efficiency, while the up-regulation of Psa and Psb in the photosystem enhanced the defense of chloroplasts against strong light. Additionally, the up-regulation of rbcl promoted the increase of photosynthetic products in the hybrids. During respiration, the down-regulation of MDH, ACO, and OGDH suppressed the tricarboxylic acid cycle (TCA cycle) and weakened respiratory consumption in the hybrids. Furthermore, we observed that the net photosynthetic rate and intercellular CO2 concentration of the hybrids were significantly higher than those of the parents. Taken together, our results suggest that the overdominant expression effect of DEGs plays a crucial role in the formation of tobacco biomass hybrid advantage. The overdominant expression effect of photosynthesis and respiration-related genes enhanced the photosynthetic capacity of the hybrids, reduced respiration consumption, and promoted the increase of tobacco biomass, thus demonstrating the obvious hybrid advantage.

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:Hybrid plants and animals grow larger and more vigorously than the parents, a common phenomenon known as hybrid vigor or heterosis. Heterosis often correlates with the genetic distance between hybridizing parents, but the mechanism for this is largely unknown. We found that genetic distance was correlated with natural variation of stress responses under the control of the circadian clock. CIRCADIAN-CLOCK-ASSOCIATED1 (CCA1) and LATE-ELONGATED-HYPOCOTYL (LHY) or CCA1 alone mediate expression amplitudes and periods of these stress-responsive genes in stress and non-stress conditions. In Arabidopsis thaliana intraspecific hybrids, genome-wide expression of many biotic and abiotic stress-responsive genes was diurnally repressed to promote biomass heterosis, which is associated with several biomass quantitative trait loci (QTLs). Expression differences in four selected stress-responsive genes among ten ecotypes could be used to predict heterosis in their hybrids. Parent plants with larger expression differences between stress-responsive genes produced higher-vigor hybrids, while those with smaller differences produced lower-vigor hybrids. Stress-responsive genes were epigenetically repressed in the hybrids under normal conditions but induced during times of stress at certain times of the day, balancing the tradeoff between stress responses and growth. Consistently, repressing the stress genes in diploids increased growth vigor. We demonstrate how hybrids manipulate diurnal stress-responsive gene expression to enhance growth vigor. Both circadian and epigenetic regulation play key roles in the altered expression of stress-responsive genes in hybrids. Our findings provide a conceptual advance and mechanistic understanding of heterosis, as well as selection criteria for parents to be effectively used for producing high-yield hybrids. Examination of gene expression in Arabidopsis thaliana F1 hybrids between Col and C24 and 3 time points using mRNA-seq

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Sweet corn: low- vs. high-yielding hybrids

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