Inactivation of the monocistronic rca gene in Anabaena variabilis suggests a physiological ribulose bisphosphate carboxylase/oxygenase activase-like function in heterocystous cyanobacteria

Inactivation of the monocistronic rca gene in Anabaena variabilis suggests a physiological... There was no discernible effect after incubating recombinant Anabaena Rubisco and carboxyarabinitol 1-phosphate with the product of the Anabaena rca gene. Since the unactivated cyanobacterial Rubisco is not readily inhibited by ribulose 1,5-bisphosphate and fallover is not observed, a genetic basis for the function of the Rubisco activase-like gene (rca) was sought. The monocistronic rca gene was inactivated in vivo and resulting mutant strains of A. variabilis were found to be incapable of synthesizing immunologically detected RCA protein. The requirement for the product of the rca gene in the light was further examined by measuring Rubisco activity in permeabilized whole cells of wild-type and rca mutant strains at different light intensities. In a 1% CO2-air atmosphere, inactivation of rca reduced the ability of A. variabilis to elevate Rubisco activity under high light (73 μmol quanta m−2 s−1), but had little effect under low light (8 μmol m−2 s−1). For air-grown cultures, differences in the rates exhibited by the wild-type and rca mutant to fully activate Rubisco during a whole-cell assay were enhanced by increases in light intensity. The significance of the rca mutation was underlined by effects on growth as, unlike the wild-type, growth rates did not increase after cells transferred from low to high light intensities. Higher exogenous CO2 concentrations (1%) were required to sustain a normal growth rate for the A. variabilis rca mutant. When grown in air levels of CO2, the rca mutant not only needed longer times to double in cell density but also exhibited greatly diminished Rubisco activity compared with the wild-type strain. Despite the unusual properties of cyanobacterial Rubisco, these results suggest a physiological role for the product of the rca gene in maximizing the activity of Rubisco in heterocystous cyanobacteria. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Molecular Biology Springer Journals

Inactivation of the monocistronic rca gene in Anabaena variabilis suggests a physiological ribulose bisphosphate carboxylase/oxygenase activase-like function in heterocystous cyanobacteria

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Publisher
Kluwer Academic Publishers
Copyright
Copyright © 1999 by Kluwer Academic Publishers
Subject
Life Sciences; Biochemistry, general; Plant Sciences; Plant Pathology
ISSN
0167-4412
eISSN
1573-5028
D.O.I.
10.1023/A:1006251808625
Publisher site
See Article on Publisher Site

Abstract

There was no discernible effect after incubating recombinant Anabaena Rubisco and carboxyarabinitol 1-phosphate with the product of the Anabaena rca gene. Since the unactivated cyanobacterial Rubisco is not readily inhibited by ribulose 1,5-bisphosphate and fallover is not observed, a genetic basis for the function of the Rubisco activase-like gene (rca) was sought. The monocistronic rca gene was inactivated in vivo and resulting mutant strains of A. variabilis were found to be incapable of synthesizing immunologically detected RCA protein. The requirement for the product of the rca gene in the light was further examined by measuring Rubisco activity in permeabilized whole cells of wild-type and rca mutant strains at different light intensities. In a 1% CO2-air atmosphere, inactivation of rca reduced the ability of A. variabilis to elevate Rubisco activity under high light (73 μmol quanta m−2 s−1), but had little effect under low light (8 μmol m−2 s−1). For air-grown cultures, differences in the rates exhibited by the wild-type and rca mutant to fully activate Rubisco during a whole-cell assay were enhanced by increases in light intensity. The significance of the rca mutation was underlined by effects on growth as, unlike the wild-type, growth rates did not increase after cells transferred from low to high light intensities. Higher exogenous CO2 concentrations (1%) were required to sustain a normal growth rate for the A. variabilis rca mutant. When grown in air levels of CO2, the rca mutant not only needed longer times to double in cell density but also exhibited greatly diminished Rubisco activity compared with the wild-type strain. Despite the unusual properties of cyanobacterial Rubisco, these results suggest a physiological role for the product of the rca gene in maximizing the activity of Rubisco in heterocystous cyanobacteria.

Journal

Plant Molecular BiologySpringer Journals

Published: Sep 29, 2004

References

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