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Gewählte Master / Diploma Thesis:

Getinet Nega Adamu (2014): Biochemical and molecular biological investigations on phloridzin formation in Malus x domestica.
Master / Diploma Thesis - Abteilung Pflanzenbau, BOKU-Universität für Bodenkultur, pp 56. UB BOKU obvsg

Data Source: ZID Abstracts
Abstract This work focuses on phloridzin - the prevalent polyphenol in apple (Malus x domestica). Despite its abundance in fruits and leaves, neither the physiological role, nor the biosynthesis are completely understood. Its effect in pathogen defense and growth regulation is controversially discussed. Systematic studies are difficult until the involved genes are known. Although the pathway is well characterized at the level of enzymes, only two of the three genes have been identified so far. For the first biosynthetic step everal candidate genes are available, but the actual physiological involvement in phloridzin formation remains to be proven. The work concentrates on two different aspects related to the physiological activity of phloridzin on the one hand and on the identification of the gene encoding the enzyme, which catalyzes the key step in phloridzin formation on the other hand. The first part exploited the availability of genetically modified plants harboring scab resistance gene or a transcription factor enhancing anthocyanin formation, respectively. From each apple tree, leaves of three developmental stages were separately analyzed. The studies showed that a slight constitutive increase of the enzymes involved in the pathway leading to flavonoid and dihydrochalcone formation occurred, which, however, cannot explain the disease resistance of the genetically modified trees. The studies on the genetically modified trees harboring the transcription factor showed that the increase of anthocyanin formation is not based on a significant increase of the enzymes catalyzing the early steps of the pathways. We assume that the transcription factor affects later enzymes such as anthocyanidin synthase or anthocyanidin reductase. The second part of this work aimed at providing an expression vector harboring the recently reported Enoyl-ACP reductase (ENRL-5) which which was suggested to be involved in phloridzin formation in apple. This was achieved by the stepwise transformation of a closely related cDNA clone (ENRL-3). In total, this required the exchange of 14 amino acids. Of this, 13 were successfully converted but the finalization was not possible in the given time frame. The expression vector will be used for future studies on the functional activity of the enzyme encoded by the ENRL-5 gene.


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