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Title: Evaluation of different genetic intervention approaches for the enhancement of carotenoids : assessment of ABA and antioxidants mediated extended shelf life in Solanum lycopersicum
Author: Moghadaszadeh Kermani, Fatemeh
ISNI:       0000 0004 8499 3117
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 2016
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Carotenoids are important groups of natural pigments belonging to the class of natural products known as isoprenoids. Lycopene is an important carotenoid commonly found in the human diet and represents 50% of carotenoids found in human serum and has a high antioxidant effect in the body. Ketocarotenoids are oxygenated carotenoids also known as xanthophylls, but this specific class of xanthophylls are rarely found in higher plants but are used commercially in animal feedstock especially aquaculture for salmon and shrimp and therefore have a large market value. In this study, different strategies were evaluated for the enhancement and production of high-value carotenoids and ketocarotenoids in tomato fruit. The mechanisms underlying the metabolic phenotype and associated physiological changes were investigated. Identification and validation of putative transcription factors (TF) followed in three parts of first objective: 1- APRR2-like (Arabidopsis pseudo-response regulator-2-like) on chromosome 6. Primary identification on APRR2-like homologue gene was initiated which needs more investigation. 2- ESB9 TF designated as Solyc06g053960. ESB9 F1 characterisation demonstrate the effect of this gene on decrease of β-carotene level in all of the lines; the next generation characterisation could lead to identification of an effective TF on pigmentation 3- putative candidate genes/regions in the S.pennelli sub ILs of 2-4 and 2-5 (Q1968 line) were studied as one strategy. The Q1968 line results indicate a significant increase in lycopene and some other metabolites. Firstly a pattern of effect was proposed for responsible regulators based on stages of ripening. Secondly two probable types of pattern that the introgressed region genes can operate for their effects were investigated. In another approach nonendogenous ketocarotenoids in tomato have been increased by combining biosynthetic optimisation [astaxanthin biosynthesis in CrtZW line (β-carotene ketolase/hydroxylase)] and transcriptional regulators [DET1(De-etiolated 1) and APRR2]. In CrtZW.APRR2 line no dramatic increase was found. Further investigation to elucidate the biochemical molecular mechanisms underlying the CrtZW.APRR2 phenotype provide a deep insight to choosing the best effective candidates for improving high-value compounds based on the TF mechanism which affect pigmentation and ripening. Through genetic crossing a new variety termed CrtZW.DET1 exhibited a significant increase in carotenoids both carotenes such as lycopene and high value ketocarotenoids. These genotypes also displayed delayed ripening the hypothesis proposed involved the modulation of abscisic acid (ABA) content in the fruit due to the depletion of β ring derived carotenoids. Associated changes in cell-wall degradation enzyme activities, hormones level and cell wall compound measurements were also observed. These data have revealed a new mechanism for improving the shelf life characteristics of fleshy fruits via introducing new pathways to plant. Firmness and weight alterations trend in shelf life experiments of CrtZW.DET1 line demonstrate a value added to this line for its unique shelf life property and its potential for improving the other crops quality.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Cartenoids ; Ketocarotenoids ; secondary metabolites ; gene manipulation ; Abscisic Acid ; plant hormons ; Ethylene ; Plant enzyme ; Firmness ; Shelflife ; Tomato ; QTL ; genetic cross ; Cell wall ; Regulatory genes