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Title: Cytokinin interconversion by StCKP1 controls potato tuber dormancy
Author: Bromley, J. R.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2009
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A novel cytokinin binding protein Solanum tuberosum Cytokinin Phosphorylase 1 (StCKP1), has been identified in tuberising stolon tips which shares regions of homology with members of the nucleosidase and phosphoribosyl transferase family. Analysis of transcripts indicates an increase in abundance of StCKP1 on tuberisation of stolon tips, and high abundance in periderm of dormant tubers. Analysis of protein abundance by immunoblotting echoes this finding and indicates StCKP1 begins to accumulate in stolon tips shortly before tuberisation, matching binding activity. Transgenic analysis of the cytological reporter gene uidA under the control of two identified promoter regions indicates StCKP1 is expressed predominantly in tuber tissue. Analysis of StCKP1 activity by HPLC and LC-MS-MS shows that StCKP1 catalyses the interconversion of free base and riboside. Kms determined for cytokinin and aiminopurine substrates indicate that StCKP1 has a higher affinity for cytokinin substrates and, of these cytokinins, displays a higher affinity for the free base catalysing ribosylation of the N9 to form the corresponding riboside. Desiree cultivars over-expressing StCKP1 under the CaMV 35S promoter exhibited an increased rate of tuberisation of stolon tips and an increase in the length of the dormant period following lifting. Over-expression of StCKP1 was found to increase in particular the chill sensitive period of dormancy, confirming results of StCKP1 knock-down by RNAi. Transcript abundance of StCKP1 at tuberisation in other cultivars including King Edward and Maris Peer was found to correlate with dormancy characteristics prescribed by the European Cultivated Potato Database and the British potato variety database.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available