title: Identification of novel genes potentially involved in somatic embryogenesis in chicory (Cichorium intybus L.).
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: UMR USTL-INRA 1281, Stress Abiotiques et Différenciation des Végétaux cultivés, Université Lille1, Cité Scientifique SN2, F-59650 Villeneuve d'Ascq, France. Anca.Lucau@univ-lille1.fr
authors.forename: Anca
authors.initials: A
authors.lastname: Lucau-Danila
authors.forename: Laurent
authors.initials: L
authors.lastname: Laborde
authors.forename: Sylvain
authors.initials: S
authors.lastname: Legrand
authors.forename: Ludovic
authors.initials: L
authors.lastname: Huot
authors.forename: David
authors.initials: D
authors.lastname: Hot
authors.forename: Yves
authors.initials: Y
authors.lastname: Lemoine
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Hilbert
authors.forename: Simon
authors.initials: S
authors.lastname: Hawkins
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Quillet
authors.forename: Theo
authors.initials: T
authors.lastname: Hendriks
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Blervacq
mesh_terms: D002473:Cell Wall / Q000378:metabolism; D018651:Cichorium intybus / Q000166:cytology / Q000196:embryology* / Q000235:genetics*; D003470:Culture Media; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005838:Genotype; D005960:Glucosides / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D010696:Phloroglucinol / Q000031:analogs & derivatives / Q000494:pharmacology; D018749:RNA, Plant / Q000235:genetics; D046509:Tissue Culture Techniques
chemical_list: D003470:Culture Media; D005960:Glucosides; D018749:RNA, Plant; C104977:Yariv reagent; D010696:Phloroglucinol