THE 46-KD FORM OF ARABIDOPSIS RUBISCO ACTIVASE CONFERS LIGHT-MEDIATED REGULATION OF RUBISCO ACTIVITY IN PLANTA

Authors: EWY, ROBERT; PORTIS JR, ARCHIE

Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/19/2000
Publication Date: 7/19/2000
Citation: Ewy, R.G., Portis Jr, A.R. 2000. Thr 46-kd form of arabidopsis rubisco activase confers light-mediated regulation of rubisco activity in planta. Plant Physiology Supplement: p.163.

Interpretive Summary:

Technical Abstract: The 43- and 46-kD isoforms of rubisco activase (RA) in Arabidopsis appear to have different functions yet work synergistically to regulate the activity of Rubisco. Kallis and Portis showed that transgenic Arabidopsis thaliana plants with only the 43-kD form of RA present did not exhibit light-mediated regulation of Rubisco. To determine if the 46-kD form of RA does confer light mediated regulation of Rubisco, we crossed a stable transgenic line of Arabidopsis that contains only the 46-kD isoform of RA with various stable transgenic lines that express only the 43-kD form of RA. The extent of light-mediated regulation of Rubisco activity was determined from the slow phase of the induction of photysynthesis. In all the 46-x 43-kD lines, as well as the Col wt. 70-80 percent of the increase of photosynthesis occurred during the slow phase of induction, indicative of light-mediated Rubisco activation. In contrast, in transgenic lines that contain only a 43-kD form of RA, the increase of photosynthesis largely occurred during the rapid phase of induction, consistent with the loss of light-mediated regulation of Rubisco activity. The results demonstrate that reintroduction of the 46-kD isoform of RA into plants that express only the 43-kD form of RA restores light-mediated regulation of Rubisco.