title: Tissue specific analysis reveals a differential organization and regulation of both ethylene biosynthesis and E8 during climacteric ripening of tomato.
abstract: BACKGROUND
  Solanum lycopersicum or tomato is extensively studied with respect to the ethylene metabolism during climacteric ripening, focusing almost exclusively on fruit pericarp. In this work the ethylene biosynthesis pathway was examined in all major tomato fruit tissues: pericarp, septa, columella, placenta, locular gel and seeds. The tissue specific ethylene production rate was measured throughout fruit development, climacteric ripening and postharvest storage. All ethylene intermediate metabolites (1-aminocyclopropane-1-carboxylic acid (ACC), malonyl-ACC (MACC) and S-adenosyl-L-methionine (SAM)) and enzyme activities (ACC-oxidase (ACO) and ACC-synthase (ACS)) were assessed.
  
  
  RESULTS
  All tissues showed a similar climacteric pattern in ethylene productions, but with a different amplitude. Profound differences were found between tissue types at the metabolic and enzymatic level. The pericarp tissue produced the highest amount of ethylene, but showed only a low ACC content and limited ACS activity, while the locular gel accumulated a lot of ACC, MACC and SAM and showed only limited ACO and ACS activity. Central tissues (septa, columella and placenta) showed a strong accumulation of ACC and MACC. These differences indicate that the ethylene biosynthesis pathway is organized and regulated in a tissue specific way. The possible role of inter- and intra-tissue transport is discussed to explain these discrepancies. Furthermore, the antagonistic relation between ACO and E8, an ethylene biosynthesis inhibiting protein, was shown to be tissue specific and developmentally regulated. In addition, ethylene inhibition by E8 is not achieved by a direct interaction between ACO and E8, as previously suggested in literature.
  
  
  CONCLUSIONS
  The Ethylene biosynthesis pathway and E8 show a tissue specific and developmental differentiation throughout tomato fruit development and ripening.
authors.forename: Bram
authors.initials: B
authors.lastname: Van de Poel
authors.forename: Nick
authors.initials: N
authors.lastname: Vandenzavel
authors.forename: Cindy
authors.initials: C
authors.lastname: Smet
authors.forename: Toon
authors.initials: T
authors.lastname: Nicolay
authors.forename: Inge
authors.initials: I
authors.lastname: Bulens
authors.forename: Ifigeneia
authors.initials: I
authors.lastname: Mellidou
authors.forename: Sandy
authors.initials: S
authors.lastname: Vandoninck
authors.forename: Maarten Latm
authors.initials: ML
authors.lastname: Hertog
authors.forename: Rita
authors.initials: R
authors.lastname: Derua
authors.forename: Stijn
authors.initials: S
authors.lastname: Spaepen
authors.forename: Jos
authors.initials: J
authors.lastname: Vanderleyden
authors.forename: Etienne
authors.initials: E
authors.lastname: Waelkens
authors.forename: Maurice P
authors.initials: MP
authors.lastname: De Proft
authors.forename: Bart M
authors.initials: BM
authors.lastname: Nicolai
authors.affiliation: Division of Mechatronics, Biostatistics and Sensors (MeBioS), Department of Biosystems (BIOSYST), KU Leuven, Willem de Croylaan 42, bus 2428, 3001 Leuven, Belgium. annemie.geeraerd@biw.kuleuven.be.
authors.forename: Annemie H
authors.initials: AH
authors.lastname: Geeraerd
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D000598:Amino Acids, Cyclic / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008190:Lyases / Q000378:metabolism; D018551:Solanum lycopersicum / Q000378:metabolism* / Q000502:physiology
chemical_list: D000598:Amino Acids, Cyclic; D005030:Ethylenes; C023863:1-aminocyclopropane-1-carboxylic acid; C036216:ethylene; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase