Functional characterisation of three transcription factors downstream of RIPENING INHIBITOR that control tomato plant morphology and fruit development and ripening

Jack Gillan

Research output: ThesisDoctoral Thesis

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Tomato (Solanum lycopersicum) is one of the most extensively consumed fruit crops worldwide. Therefore, the identification of genes central to fruit development and ripening, which influence fruit quality, remains an important objective. Previously, the RIPENING INHIBITOR (RIN) transcription factor was shown to be a global ripening-regulator. Current breeding strategies have utilised the heterozygous rin mutation as fruits display reduced fruit softening, expanding distribution and storage opportunities, despite negatively impacting both fruit colour and flavour. Therefore, downstream targets of RIN have been identified in order to facilitate a more targeted approach for tomato improvement. Using Systems Biology outputs derived from transcriptomics performed over fruit development and ripening, three transcription factors were identified, including the direct RIN target ZINC FINGER PROTEIN INDETERMINATE DOMAIN 2 (ZFPIDD2), and predicted indirect RIN targets: ZINC-FINGER PROTEIN ZPR1 and HEAT SHOCK TRANSCRIPTION FACTOR A3 (HSFA2). These transcription factors were manipulated through the insertion of a knock-down RNAi construct under constitutive control (CaM35S).
Down-regulation of ZFPIDD2 resulted in several plant developmental differences, including reduced internode lengths, elevated non-vegetative biomass with increased fruit number, size and total yield. Fruits displayed a partial uncoupling of ripening: with significant reduction to fruit softening and potential extension to shelf-life, combined with elevated colour-associated ripening and carotenoid content. Therefore, the improvements of the rin mutation are maintained, while enhancing yield and colour development. Similar ripening-related improvements were demonstrated by ZPR1 transgenic lines, containing the knock-down construct, with altered phenolics and less development and fruit yield-associated differences. HSFA2 transgenic lines exhibited phenotypes similar to hy5 down-regulation: including extended shoot growth during early development, paler leaves and reduced carotenoid content in ripe fruits. Despite not providing targeted improvements, all three transcription factors were shown to be important for development and fruit ripening-related quality traits. This study provides further insight into transcriptional control of tomato development and ripening, and future approaches to trait improvement using the emerging technologies associated with gene editing.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Fraser, Paul, Supervisor
Award date1 Jun 2019
Publication statusUnpublished - 2018


  • Tomato
  • Ripening
  • Transcription factors
  • Ripening inhibitor
  • RIN

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