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Title: REGULATION OF RUBISCO VIA RUBISCO ACTIVASE: INTEGRATION OF CONTROL BY THE STROMAL ADP/ATP RATIO AND REDOX STATE

Author
item PORTIS JR, ARCHIE
item EWY, ROBERT
item ZHANG, NING - PLANT BIOLOGY UOFI URBANA
item KALLIS, RUSSELL - CROP SCIENCES UOFI URBANA

Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/19/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Rubisco activase regulates Rubisco by utilizing its ATP hydrolysis activity to remove the inhibitory sugar phosphates. The activity of Rubsico is typically observed to co-vary with the overall rate of photosynthesis when light intensity varies, but less commonly is also reduced when photosynthesis is restricted by product (triose phosphate) utilization. The decrease in the ATPase and Rubisco activation activities of Rubisco activase by an increase in the ratio of ADP/ATP, which occurs under limitations in triose phosphate utilization, can account for the latter. An explicit mechanism that can account for the light modulation of Rubisco activity was not apparent until our recent discovery that activase activity is also modulated by redox changes, which are specifically mediated by thioredoxin-f. Redox alters the response of the activase to the ADP/ATP ratio, thereby integrating the control by these two signaling pathways. Redox regulation is dependent on the larger of the two isoforms of Rubisco activase, which contains the critical cysteine residues. Thus, redox regulation has revealed the biochemical significance for alternative splicing of the activase gene. Evidence for redox regulation obtained from in vitro studies of the isolated proteins and in vivo studies using transgenic Arabidopsis plants, will be presented. Some unresolved issues requiring further research also will be discussed.