title: Overexpression of plum auxin receptor PslTIR1 in tomato alters plant growth, fruit development and fruit shelf-life characteristics.
abstract: BACKGROUND
  TIR1-like proteins are F-box auxin receptors. Auxin binding to the F-box receptor proteins promotes the formation of SCF(TIR1) ubiquitin ligase complex that targets the auxin repressors, Aux/IAAs, for degradation via the ubiquitin/26S proteasome pathway. The release of auxin response factors (ARFs) from their Aux/IAA partners allows ARFs to mediate auxin-responsive changes in downstream gene transcription. In an attempt to understand the potential role of auxin during fruit development, a plum auxin receptor, PslTIR1, has previously been characterized at the cellular, biochemical and molecular levels, but the biological significance of this protein is still lacking. In the present study, tomato (Solanum lycopersicum) was used as a model to investigate the phenotypic and molecular changes associated with the overexpression of PslTIR1.
  
  
  RESULTS
  The findings of the present study highlighted the critical role of PslTIR1 as positive regulator of auxin-signalling in coordinating the development of leaves and fruits. This was manifested by the entire leaf morphology of transgenic tomato plants compared to the wild-type compound leaf patterning. Moreover, transgenic plants produced parthenocarpic fruits, a characteristic property of auxin hypersensitivity. The autocatalytic ethylene production associated with the ripening of climacteric fruits was not significantly altered in transgenic tomato fruits. Nevertheless, the fruit shelf-life characteristics were affected by transgene presence, mainly through enhancing fruit softening rate. The short shelf-life of transgenic tomatoes was associated with dramatic upregulation of several genes encoding proteins involved in cell-wall degradation, which determine fruit softening and subsequent fruit shelf-life.
  
  
  CONCLUSIONS
  The present study sheds light into the involvement of PslTIR1 in regulating leaf morphology, fruit development and fruit softening-associated ripening, but not autocatalytic ethylene production. The results demonstrate that auxin accelerates fruit softening independently of ethylene action and this is probably mediated through the upregulation of many cell-wall metabolism genes.
authors.affiliation: Department of Plant Agriculture, University of Guelph, Vineland Station, ON, Canada. ielshark@uoguelph.ca.|Damanhour University, Faculty of Agriculture, Damanhour, Egypt. ielshark@uoguelph.ca.
authors.forename: I
authors.initials: I
authors.lastname: El-Sharkawy
authors.affiliation: Department of Plant Agriculture, University of Guelph, Vineland Station, ON, Canada. ssherif@uoguelph.ca.|Damanhour University, Faculty of Agriculture, Damanhour, Egypt. ssherif@uoguelph.ca.
authors.forename: S
authors.initials: S
authors.lastname: Sherif
authors.affiliation: Department of Plant Agriculture, University of Guelph, Vineland Station, ON, Canada. welkayal@uoguelph.ca.
authors.forename: W
authors.initials: W
authors.lastname: El Kayal
authors.affiliation: The University of Sydney, Faculty of Agriculture, Sydney, Australia. brian.jones@sydney.edu.au.
authors.forename: B
authors.initials: B
authors.lastname: Jones
authors.affiliation: Chongqing University, Genetic Engineering Research Center, Bioengineering College, Chongqing, China. zhengguoli@cqu.edu.cn.
authors.forename: Z
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada. asulliva@uoguelph.ca.
authors.forename: A J
authors.initials: AJ
authors.lastname: Sullivan
authors.affiliation: Department of Plant Agriculture, University of Guelph, Vineland Station, ON, Canada. jsubrama@uoguelph.ca.
authors.forename: Subramanian
authors.initials: S
authors.lastname: Jayasankar
mesh_terms: D005030:Ethylenes / Q000096:biosynthesis; D005638:Fruit / Q000254:growth & development* / Q000378:metabolism; D007210:Indoleacetic Acids; D018551:Solanum lycopersicum / Q000235:genetics* / Q000254:growth & development; D063245:Plant Development; D010937:Plant Growth Regulators / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics; D000068242:Prunus domestica / Q000235:genetics* / Q000254:growth & development; D011956:Receptors, Cell Surface / Q000235:genetics*; D015398:Signal Transduction
chemical_list: D005030:Ethylenes; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C046131:auxin receptor, plant; C036216:ethylene