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Title: LIGHT MODULATION OF RUBISCO IN ARABIDOPSIS PLANTS REQUIRES THE ABILITY TO REDOX REGULATE RUBISCO ACTIVASE

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

Submitted to: Photosynthetic CO2 Assimilating Enzymes Rubisco and Pepc Conference
Publication Type: Proceedings
Publication Acceptance Date: 8/25/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: To directly address the relationship between redox regulation of activase and modulation of Rubisco activity by light intensity in Arabidopsis, we transformed the rca-minus mutant, which does not express Rubisco activase, to obtain plants that express various forms of Rubisco activase. Rubisco activity was rapidly increased by illumination in plants expressing only the shorter isoform but the activity was not down-regulated at intensities limiting for photosynthesis. In plants expressing only larger isoform, Rubisco activity was down-regulated at limiting light, but activity increased only slowly at saturating light intensities. Light regulation of Rubisco was similar to wildtype plants in the progeny of a cross of these two transformants in which both isoforms were present. When the ability of larger isoform to be redox regulated was eliminated by replacement of critical cyteine residues, the resulting transgenic plants also lost the ability to down-regulate Rubisco under limiting light. Other characteristics of the various transgenic plants will be presented. Our findings clearly indicate that light regulation of Rubisco under limiting light requires the ability to regulate the activity of the activase protein by redox changes in stroma. Implications of these results for light modulation of Rubisco in tobacco and other species that lack larger isoform will be discussed.