Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Alterations to hormone regulated defense and stress response networks contribute to the greater growth of Arabidopsis F1 hybrids

ABSTRACT: Heterosis, or hybrid vigor, has been exploited in agriculture to deliver increases in crop yields for over a century, yet the molecular basis is not well understood We have studied the transcriptomes of 15 day old seedlings from intraspecific Arabidopsis hybrids with varying levels of heterosis and their parental lines in order to identify drivers of heterosis. The patterns of altered gene expression in the hybrids point to a reduction in basal defense levels that could reflect the antagonism between plant immunity and plant growth. Associated with this theme are changes to the salicylic acid and auxin regulated networks which are known to control abiotic and biotic defense responses as well as being important regulators of plant growth. Increased auxin response correlates with the heterotic phenotype of greater leaf cell numbers, whereas reduced salicylic acid levels and response promotes increased leaf cell size in hybrids involving C24. By manipulating salicylic acid levels in each of our hybrid systems, we can alter levels of heterosis, promote additional growth in the hybrids, and generate increased growth in the parents, especially C24. Aerial tissues of 15 days after sowing seedlings from C24, Ler, Col and their reciprocal hybrid offspring. In total 7 biological replicates for both the C24 and Ler parents, 2 biological replicates for Col, 10 biological replicates for C24/Ler and 4 biological replicates for both C24/Col and Col/Ler were sequenced and analysed. Each replicated consisted of a pools of 5-15 seedlings (see publication for more details)

ORGANISM(S): Arabidopsis thaliana

SUBMITTER: Michael Groszmann

PROVIDER: E-GEOD-64475 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Hormone-regulated defense and stress response networks contribute to heterosis in Arabidopsis F1 hybrids.

Groszmann Michael M Gonzalez-Bayon Rebeca R Lyons Rebecca L RL Greaves Ian K IK Kazan Kemal K Peacock W James WJ Dennis Elizabeth S ES

Proceedings of the National Academy of Sciences of the United States of America 20151102 46

Plant hybrids are extensively used in agriculture to deliver increases in yields, yet the molecular basis of their superior performance (heterosis) is not well understood. Our transcriptome analysis of a number of Arabidopsis F1 hybrids identified changes to defense and stress response gene expression consistent with a reduction in basal defense levels. Given the reported antagonism between plant immunity and growth, we suggest that these altered patterns of expression contribute to the greater ...[more]

PMID: 26527659

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Project description:F1 hybrids can outperform their parents in yield and vegetative biomass, features of hybrid vigor which form the basis of the hybrid seed industry. The yield advantage of the F1 is lost in the F2 and subsequent generations. In Arabidopsis, from F2 plants which have a F1 âlike phenotype, we have by recurrent selection produced pure breeding F5/F6 lines âHybrid Mimicsâ, in which the characteristics of the F1 Hybrid are stabilized. These Hybrid Mimic lines, like the F1 Hybrid, have larger leaves than the parent plant, the leaves having increased photosynthetic cell numbers, and in some lines increased size of cells, suggesting an increased supply of photosynthate. A comparison of the differentially expressed genes in the F1 Hybrid with those of eight Hybrid Mimic lines has identified metabolic pathways altered in both; these pathways include down regulation of defense response pathways and altered abiotic response pathways. F6 Hybrid Mimic lines are mostly homozygous at each locus in the genome yet retain the large F1-like phenotype. Many alleles in the F6 plants, when they are homozygous, have expression levels different to the level in the parent. We consider this altered expression to be a consequence of trans-regulation of genes from one parent by genes from the other parent. Transregulation could also arise from epigenetic modifications in the F1. The pure breeding Hybrid Mimics have been valuable in probing the mechanisms of hybrid vigor and may also prove to be useful hybrid vigor equivalents in agriculture. Plant Materials: Seeds were sterilized and sown onto plates containing MSN medium (MS salts supplemented with 1% (w/v) sucrose, pH7 with KOH, 0.6% wt/vol Noble agar). After 2 days at 4Â°C, the plates were transferred to a growth room with conditions of 22 Â°C/18 Â°C (day/night) and 16h light/8h dark cycle under Philips Cool Daylight TLD 58W/840 fluorescent tubes providing a photosynthetic photon flux density of 130 - 150Î¼mol photons m-2Â·s-1 as measured using a quantum meter (Model MQ-200 calibrated for electric light source, Apogee). At 18 days after sowing (DAS), the plants were transferred to soil and grown to the reproductive stage in a growth room with controlled light conditions (OSRAM L 36W/865 LumLux Daylight, 130 - 150Î¼mol photons m-2Â·s-1). To minimize the edge effects, the positioning of both plates and trays on the shelves was rotated every two days. All the plants were grown under the condition described above unless specified. Plant sample preparation and RNA extraction: For the transcriptomes of 15 DAS plants, the aerial tissues of 15 day seedlings were sampled. For the transcriptomes of plants at 28 DAS, the four largest leaves of 28 day plants from the parental lines (C24, Ler), the reciprocal Hybrids and eight F4 Hybrid Mimic lines were harvested. Each sample comprised a pool of five plants. Two biological replicates of each sample were sequenced. Total RNA was isolated using QIAGEN RNeasy MiniKitTM following the product instructions. To eliminate variation in experimental conditions in different positions in the growth room, nine F4 plant lines were divided into two batches to ensure plants were grown on the same shelves in each experiment. Parental lines C24 and Ler and the F1 Hybrid from which the F4 lines derived from were grown under the same conditions in each experiment as controls. The first batch including samples C24 (RepA and RepB), Ler (RepA and RepB), C24 x Ler F1, F4-L1-1, F4-L1-2, F4-L2-1, F4-L2-2 and F4-S-1 were grown under the condition describe above, we also sampled the five smallest C24 seedlings and five smallest Ler seedlings among the population (n = 50); the mRNA sequencing was performed by the Australian Genome Research Facility (AGRF). The second batch including C24 (RepC and RepD), Ler (RepC and RepD), Ler x C24 F1 Hybrid, F4-L3-1, F4-L3-2, F4-L4-1 and F4-L4-2 were grown in the same light intensity as above but under different light tubes (SYLVANIA PREMIUM extra FL36W/865 Super Daylight deluxe light tube). For the transcriptome of the two F6 Hybrid Mimic lines at 15 DAS, C24, Ler, Ler x C24 F1 Hybrids and three siblings from each F6 line (L3-1-1-2 and L4-2-1-2) were grown on MS medium (MS salts supplemented with 1% (w/v) sucrose, pH 5.7 with KOH, add 0.6% wt/vol agar) with controlled light conditions (SYLVANIA PREMIUM extra FL36W/865 Super Daylight deluxe, 130 - 150Î¼mol photons m-2Â·s-1). The mRNA sequencing service was provided by AGRF on the Illumina platform, 100bp paired ends.

Project description:F1 hybrids can outperform their parents in yield and vegetative biomass, features of hybrid vigor which form the basis of the hybrid seed industry. The yield advantage of the F1 is lost in the F2 and subsequent generations. In Arabidopsis, from F2 plants which have a F1like phenotype, we have by recurrent selection produced pure breeding F5/F6 linesHybrid Mimics, in which the characteristics of the F1 Hybrid are stabilized. These Hybrid Mimic lines, like the F1 Hybrid, have larger leaves than the parent plant, the leaves having increased photosynthetic cell numbers, and in some lines increased size of cells, suggesting an increased supply of photosynthate. A comparison of the differentially expressed genes in the F1 Hybrid with those of eight Hybrid Mimic lines has identified metabolic pathways altered in both; these pathways include down regulation of defense response pathways and altered abiotic response pathways. F6 Hybrid Mimic lines are mostly homozygous at each locus in the genome yet retain the large F1-like phenotype. Many alleles in the F6 plants, when they are homozygous, have expression levels different to the level in the parent. We consider this altered expression to be a consequence of trans-regulation of genes from one parent by genes from the other parent. Transregulation could also arise from epigenetic modifications in the F1. The pure breeding Hybrid Mimics have been valuable in probing the mechanisms of hybrid vigor and may also prove to be useful hybrid vigor equivalents in agriculture. Plant Materials: Seeds were sterilized and sown onto plates containing MSN medium (MS salts supplemented with 1% (w/v) sucrose, pH7 with KOH, 0.6% wt/vol Noble agar). After 2 days at 4°C, the plates were transferred to a growth room with conditions of 22°C/18°C (day/night) and 16h light/8h dark cycle under Philips Cool Daylight TLD 58W/840 fluorescent tubes providing a photosynthetic photon flux density of 130 - 150 umol photons m-2·s-1 as measured using a quantum meter (Model MQ-200 calibrated for electric light source, Apogee). At 18 days after sowing (DAS), the plants were transferred to soil and grown to the reproductive stage in a growth room with controlled light conditions (OSRAM L 36W/865 LumLux Daylight, 130 - 150 umol photons m-2·s-1). To minimize the edge effects, the positioning of both plates and trays on the shelves was rotated every two days. All the plants were grown under the condition described above unless specified. Plant sample preparation and RNA extraction: For the transcriptomes of 15 DAS plants, the aerial tissues of 15 day seedlings were sampled. For the transcriptomes of plants at 28 DAS, the four largest leaves of 28 day plants from the parental lines (C24, Ler), the reciprocal Hybrids and eight F4 Hybrid Mimic lines were harvested. Each sample comprised a pool of five plants. Two biological replicates of each sample were sequenced. Total RNA was isolated using QIAGEN RNeasy MiniKitTM following the product instructions. To eliminate variation in experimental conditions in different positions in the growth room, nine F4 plant lines were divided into two batches to ensure plants were grown on the same shelves in each experiment. Parental lines C24 and Ler and the F1 Hybrid from which the F4 lines derived from were grown under the same conditions in each experiment as controls. The first batch including samples C24 (RepA and RepB), Ler (RepA and RepB), C24 x Ler F1, F4-L1-1, F4-L1-2, F4-L2-1, F4-L2-2 and F4-S-1 were grown under the condition describe above, we also sampled the five smallest C24 seedlings and five smallest Ler seedlings among the population (n = 50); the mRNA sequencing was performed by the Australian Genome Research Facility (AGRF). The second batch including C24 (RepC and RepD), Ler (RepC and RepD), Ler x C24 F1 Hybrid, F4-L3-1, F4-L3-2, F4-L4-1 and F4-L4-2 were grown in the same light intensity as above but under different light tubes (SYLVANIA PREMIUM extra FL36W/865 Super Daylight deluxe light tube). For the transcriptome of the two F6 Hybrid Mimic lines at 15 DAS, C24, Ler, Ler x C24 F1 Hybrids and three siblings from each F6 line (L3-1-1-2 and L4-2-1-2) were grown on MS medium (MS salts supplemented with 1% (w/v) sucrose, pH 5.7 with KOH, add 0.6% wt/vol agar) with controlled light conditions (SYLVANIA PREMIUM extra FL36W/865 Super Daylight deluxe, 130 - 150 umol photons m-2Â·s-1). The mRNA sequencing service was provided by AGRF on the Illumina platform, 100bp paired ends.

Dataset Information

Alterations to hormone regulated defense and stress response networks contribute to the greater growth of Arabidopsis F1 hybrids

Publications

Hormone-regulated defense and stress response networks contribute to heterosis in Arabidopsis F1 hybrids.

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