Author
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KALLIS, RUSS - SCH LIFE SCI UOFI URB IL |
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PORTIS JR, ARCHIE |
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Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only Publication Acceptance Date: 8/6/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Arabidopsis rubisco activase cDNA coding for the 42kD isoform were altered in an ATP binding site by site directed mutagenesis. Amino acid position 111 was changed from a glutamine Q, to either a serine S, glutamate E, or aspartate D. Rubisco activation by recombinant enzymes was measured in response to various ADP/ATP ratios. Recombinant enzymes Q111D and Q111E demonstrated rubisco activation at ADP/ATP ratios that inhibited rubisco activation by the 42kD recombinant wild type enzyme to the level of spontaneous activation. In planta transformation of the rca mutant with altered rubisco activase cDNA has resulted in plants that grow at ambient CO2. Rubisco activation state was measure in wild type Arabidopsis and rca complemented with Q111E. Activation state was measured at 15, 30, and 60 minutes at saturing light (600uE m**-2s**-1), then at 15, 30, and 60 minutes after a change to subsaturating light (35uEm**-2s**-1), and at 60 minutes after a return to saturating light. Both the wild type and rca complemented with Q111E had a high rubisco activation state during the initial and final saturated light phases of the experiment. However, rca complemented with Q111E maintained a high activation state after the change to and throughout low illumination while the wild type plant showed a 50 percent drop of rubisco activation upon transfer to low light. In these initial experiments, the persistently high activation state demonstrated by Arabidopsis rca complemented with the Q111E enzyme is consistent with the previously reported in vito results. |
