Interaction of Herbicides and Quinone with the QB-Protein of the Diuron-Resistant Chlamydomonas reinhardtii Mutant Dr2

AUTOR(ES)

Haworth, Philip

RESUMO

We have used the diuron-resistant Dr2 mutant of Chlamydomonas reinhardtii which is altered in the 32 kilodalton QB-protein at amino acid 219 (valine to isoleucine), to investigate the interactions of herbicides and plastoquinone with the 32 kilodalton QB-protein. The data contained in this report demonstrate that the effects of this mutation are different from those of the more completely characterized mutant which confers extreme resistance to triazines in higher plants. The mutation in C. reinhardtii Dr2 confers only slight resistance to a number of inhibitors of photosynthetic electron transport. Extreme triazine resistance results from an increase in the binding constant of the herbicide with the 32 kilodalton QB-protein, in contrast the diuron binding constant for chloroplasts isolated from wild-type (sensitive) Chlamydomonas and the resistant Dr2 are indistinguishable. We conclude that the altered structure in the 32 kilodalton QB-protein of Dr2 does not directly affect the diuron binding site. This mutation appears to alter the steric properties of the binding protein in such a way that diuron and plastoquinone do not directly compete for binding. This steric perturbation confers mild resistance to other herbicidal inhibitors of photosynthesis and alters the kinetics of QA to QB electron transfer.

Documentos Relacionados

• Light-dependent degradation of the QB-protein in isolated pea thylakoids
• Mutants Resistant to anti-Microtubule Herbicides Map to a Locus on the Uni Linkage Group in Chlamydomonas Reinhardtii
• Isolation and Characterization of a Mutant of Chlamydomonas reinhardtii Deficient in the CO2 Concentrating Mechanism 1
• Photoconversion of Photochlorophyllide in the y-1 Mutant of Chlamydomonas reinhardtii
• Isolation and genetic analysis of Chlamydomonas reinhardtii strains resistant to cadmium.