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Characterization of expressed sequence tags obtained by SSH during somatic embryogenesis in Cichorium intybus L.

ABSTRACT: BACKGROUND: Somatic embryogenesis (SE) is an asexual propagation pathway requiring a somatic-to-embryonic transition of differentiated somatic cells toward embryogenic cells capable of producing embryos in a process resembling zygotic embryogenesis. In chicory, genetic variability with respect to the formation of somatic embryos was detected between plants from a population of Cichorium intybus L. landrace Koospol. Though all plants from this population were self incompatible, we managed by repeated selfing to obtain a few seeds from one highly embryogenic (E) plant, K59. Among the plants grown from these seeds, one plant, C15, was found to be non-embryogenic (NE) under our SE-inducing conditions. Being closely related, we decided to exploit the difference in SE capacity between K59 and its descendant C15 to study gene expression during the early stages of SE in chicory. RESULTS: Cytological analysis indicated that in K59 leaf explants the first cell divisions leading to SE were observed at day 4 of culture. In contrast, in C15 explants no cell divisions were observed and SE development seemed arrested before cell reactivation. Using mRNAs isolated from leaf explants from both genotypes after 4 days of culture under SE-inducing conditions, an E and a NE cDNA-library were generated by SSH. A total of 3,348 ESTs from both libraries turned out to represent a maximum of 2,077 genes. In silico subtraction analysis sorted only 33 genes as differentially expressed in the E or NE genotype, indicating that SSH had resulted in an effective normalisation. Real-time RT-PCR was used to verify the expression levels of 48 genes represented by ESTs from either library. The results showed preferential expression of genes related to protein synthesis and cell division in the E genotype, and related to defence in the NE genotype. CONCLUSION: In accordance with the cytological observations, mRNA levels in explants from K59 and C15 collected at day 4 of SE culture reflected differential gene expression that presumably are related to processes accompanying early stages of direct SE. The E and NE library obtained thus represent important tools for subsequent detailed analysis of molecular mechanisms underlying this process in chicory, and its genetic control.

SUBMITTER: Legrand S

PROVIDER: S-EPMC1913917 | biostudies-literature | 2007

REPOSITORIES: biostudies-literature

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Characterization of expressed sequence tags obtained by SSH during somatic embryogenesis in Cichorium intybus L.

Legrand Sylvain S Hendriks Theo T Hilbert Jean-Louis JL Quillet Marie-Christine MC

BMC plant biology 20070606

<h4>Background</h4>Somatic embryogenesis (SE) is an asexual propagation pathway requiring a somatic-to-embryonic transition of differentiated somatic cells toward embryogenic cells capable of producing embryos in a process resembling zygotic embryogenesis. In chicory, genetic variability with respect to the formation of somatic embryos was detected between plants from a population of Cichorium intybus L. landrace Koospol. Though all plants from this population were self incompatible, we managed ...[more]

PMID: 17553130

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Project description:BACKGROUND: In our laboratory we use cultured chicory (Cichorium intybus) explants as a model to investigate cell reactivation and somatic embryogenesis and have produced 2 chicory genotypes (K59, C15) sharing a similar genetic background. K59 is a responsive genotype (embryogenic) capable of undergoing complete cell reactivation i.e. cell de- and re-differentiation leading to somatic embryogenesis (SE), whereas C15 is a non-responsive genotype (non-embryogenic) and is unable to undergo SE. Previous studies 1 showed that the use of the beta-D-glucosyl Yariv reagent (beta-GlcY) that specifically binds arabinogalactan-proteins (AGPs) blocked somatic embryo production in chicory root explants. This observation indicates that beta-GlcY is a useful tool for investigating somatic embryogenesis (SE) in chicory. In addition, a putative AGP (DT212818) encoding gene was previously found to be significantly up-regulated in the embryogenic K59 chicory genotype as compared to the non-embryogenic C15 genotype suggesting that this AGP could be involved in chicory re-differentiation 2. In order to improve our understanding of the molecular and cellular regulation underlying SE in chicory, we undertook a detailed cytological study of cell reactivation events in K59 and C15 genotypes, and used microarray profiling to compare gene expression in these 2 genotypes. In addition we also used beta-GlcY to block SE in order to identify genes potentially involved in this process. RESULTS: Microscopy confirmed that only the K59, but not the C15 genotype underwent complete cell reactivation leading to SE formation. beta-GlcY-treatment of explants blocked in vitro SE induction, but not cell reactivation, and induced cell wall modifications. Microarray analyses revealed that 78 genes were differentially expressed between induced K59 and C15 genotypes. The expression profiles of 19 genes were modified by beta-GlcY-treatment. Eight genes were both differentially expressed between K59 and C15 genotypes during SE induction and transcriptionally affected by beta-GlcY-treatment: AGP (DT212818), 26 S proteasome AAA ATPase subunit 6 (RPT6), remorin (REM), metallothionein-1 (MT1), two non-specific lipid transfer proteins genes (SDI-9 and DEA1), 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase), and snakin 2 (SN2). These results suggest that the 8 genes, including the previously-identified AGP gene (DT212818), could be involved in cell fate determination events leading to SE commitment in chicory. CONCLUSION: The use of two different chicory genotypes differing in their responsiveness to SE induction, together with beta-GlcY-treatment represented an efficient tool to discriminate cell reactivation from the SE morphogenetic pathway. Such an approach, together with microarray analyses, permitted us to identify several putative key genes related to the SE morphogenetic pathway in chicory.

Project description:In Cichorium intybus, macroscopic and histological modifications were identified during in vitro cell reactivation and morphogenesis events. The relationships between these modifications and transcript profiles of genes were investigated. Two chicory genotypes derived from the Hungarian landrace Koospol, were tested: K59 is a responsive genotype (embryogenic), as it undergoes cell de- and re-differentiation that leads to somatic embryogenesis (SE). C15 is an unresponsive genotype (nonembryogenic), unable to express this morphogenetic pattern. Previously studies showed that addition of beta-D-glucosyl Yariv reagent (BGlcY), a synthetic phenyl-glycoside that specifically binds arabinogalactan-proteins (AGPs), to the culture medium blocked somatic embryogenesis in chicory root explants in a concentration-dependent manner with complete inhibition of induction occurring at 250 µM of BGlcY (Chapmann et al. 2000a). A putative AGP (DT212818) encoding gene was previously found significantly over-expressed in the K59 as compared to the C15 and was suggested to be involved in chicory re-differentiation. To better understand the cell reactivation events, a treatment with BGlcY was applied in order to precipitate AGPs in muro and to block the in vitro cell re-differentiation processes. The two different genotypes together with BGlcY represented an original tool to discriminate cell reactivation events from cell fate determination. Microscopy, biochemical and transcriptome analyses showed that in vitro SE in chicory was blocked during BGlcY-treatment but cell reactivation still occurred. Consequently, AGP (DT212818) seems to be only important in cell fate determination leading to SE commitment. Gene expression profiles showed in addition to the AGP, other proteins could play a role in SE determination: 26S proteasome AAA ATPase subunit 6 (RPT6), remorin (REM), metallothionein 1 (MT1), 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase). Cell wall events during BGlcY-treatment were observed and discussed.

Project description:Heat stress is one of the major problems in agriculturally important cereal crops, especially wheat. Here, we have constructed a subtracted cDNA library from the endosperm of HS-treated (42°C for 2 h) wheat cv. HD2985 by suppression subtractive hybridization (SSH). We identified ~550 recombinant clones ranging from 200 to 500 bp with an average size of 300 bp. Sanger's sequencing was performed with 205 positive clones to generate the differentially expressed sequence tags (ESTs). Most of the ESTs were observed to be localized on the long arm of chromosome 2A and associated with heat stress tolerance and metabolic pathways. Identified ESTs were BLAST search using Ensemble, TriFLD, and TIGR databases and the predicted CDS were translated and aligned with the protein sequences available in pfam and InterProScan 5 databases to predict the differentially expressed proteins (DEPs). We observed eight different types of post-translational modifications (PTMs) in the DEPs corresponds to the cloned ESTs-147 sites with phosphorylation, 21 sites with sumoylation, 237 with palmitoylation, 96 sites with S-nitrosylation, 3066 calpain cleavage sites, and 103 tyrosine nitration sites, predicted to sense the heat stress and regulate the expression of stress genes. Twelve DEPs were observed to have transmembrane helixes (TMH) in their structure, predicted to play the role of sensors of HS. Quantitative Real-Time PCR of randomly selected ESTs showed very high relative expression of HSP17 under HS; up-regulation was observed more in wheat cv. HD2985 (thermotolerant), as compared to HD2329 (thermosusceptible) during grain-filling. The abundance of transcripts was further validated through northern blot analysis. The ESTs and their corresponding DEPs can be used as molecular marker for screening or targeted precision breeding program. PTMs identified in the DEPs can be used to elucidate the thermotolerance mechanism of wheat-a novel step toward the development of "climate-smart" wheat.

Project description:In Cichorium intybus, macroscopic and histological modifications were identified during in vitro cell reactivation and morphogenesis events. The relationships between these modifications and transcript profiles of genes were investigated. Two chicory genotypes derived from the Hungarian landrace Koospol, were tested: K59 is a responsive genotype (embryogenic), as it undergoes cell de- and re-differentiation that leads to somatic embryogenesis (SE). C15 is an unresponsive genotype (nonembryogenic), unable to express this morphogenetic pattern. Previously studies showed that addition of beta-D-glucosyl Yariv reagent (BGlcY), a synthetic phenyl-glycoside that specifically binds arabinogalactan-proteins (AGPs), to the culture medium blocked somatic embryogenesis in chicory root explants in a concentration-dependent manner with complete inhibition of induction occurring at 250 ÂµM of BGlcY (Chapmann et al. 2000a). A putative AGP (DT212818) encoding gene was previously found significantly over-expressed in the K59 as compared to the C15 and was suggested to be involved in chicory re-differentiation. To better understand the cell reactivation events, a treatment with BGlcY was applied in order to precipitate AGPs in muro and to block the in vitro cell re-differentiation processes. The two different genotypes together with BGlcY represented an original tool to discriminate cell reactivation events from cell fate determination. Microscopy, biochemical and transcriptome analyses showed that in vitro SE in chicory was blocked during BGlcY-treatment but cell reactivation still occurred. Consequently, AGP (DT212818) seems to be only important in cell fate determination leading to SE commitment. Gene expression profiles showed in addition to the AGP, other proteins could play a role in SE determination: 26S proteasome AAA ATPase subunit 6 (RPT6), remorin (REM), metallothionein 1 (MT1), 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase). Cell wall events during BGlcY-treatment were observed and discussed. Gene expression of K59 explants induced (d4) was compared with gene expression of K59 explants without induction (d0). Gene expression of K59 explants induced in the presence of BGlcY (Y+; d4) was next compared with gene expression of K59 explants induced in the absence of BGlcY (Y-; d4). Similar comparisons were made for C15 leaf explants. To link up both genotypes, direct comparison was done between gene expression of K59 explants without induction (d0) and C15 explants without induction (d0). Three biological replicates were used for each analysed condition. Dye labelling for each paired sample was reversed in two subsequent individual hybridizations giving rise to a total of six hybridizations per condition except for the K59_D0_vs_C15_D0 condition.

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Characterization of expressed sequence tags obtained by SSH during somatic embryogenesis in Cichorium intybus L.

Publications

Characterization of expressed sequence tags obtained by SSH during somatic embryogenesis in Cichorium intybus L.

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