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Title: Regulation of Rubisco activity in C₃ and CAM Mesembryanthemum crystallinum L.
Author: Davies, Barnaby Nicholas
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2006
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This study combined in vivo leaf gas exchange, chlorophyll fluorescence, and instantaneous carbon isotope discrimination (D) analyses with in vitro measurement of Rubisco and PEPc activity and transcript abundance of key Rubisco and PEPc regulatory enzymes, Rubisco activase (RCA) and PEPc kinase (PPCKI ), and RCA protein abundance, to provide a novel molecular perspective on the co-regulation of carboxylase activity in M. crystallinum. In C3 M. crystallinum, Rubisco activation state was highest during the photoperiod. C3 Rubisco activity remained uniform diurnally, mirrored by the pattern of stable CO2 assimilation rate and protein abundance of both RCA isoforms, RCA1 and RCA2. RACE-PCR was used to identify RCA2 as the larger isoform in M. crystallinum. A marked decrease in RCA2 protein occurred during CAM induction, coincident with increased PEPc protein abundance and maximal PEPc activity. Diurnal Rubisco activity was regulated independent of light intensity and electron transport rate (ETR) following CAM induction. Rubisco activation state in CAM M. crystallinum was increased during the latter half of the photoperiod (mid CAM Phase III - Phase IV), coincident with low apparent PEPc activity and the final stages of titratable acidity breakdown. Increased RCA1 protein abundance during mid-CAM Phase III was observed coincident with an increase in Rubisco activation state of approximately one third. Modulation of diurnal Rubisco activity by RCA1 represented a potential regulatory mechanism unique to the CAM mode of M. crystallinum.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available