Genetic analysis of mutant clones of Chlamydomonas reinhardtii defective in potassium transport

Abstract

Mutant clones of Chlamydomonas reinhardtii defective for potassium transport were isolated and characterized. Of the four genes identified, three - TRK1, TRK2 and TRK3 encode high-affinity transport functions, and one gene, HKR1, encodes a low-affinity transport function. Characterization of the potassium dependence of recombinants possessing two mutant trk alleles suggests that the protein products of TRK2 and TRK3 interact functionally, and that TRK1 may serve a regulatory function. The mutant clone defective for a low-affinity potassium transporter was isolated by mutagenizing trk2-1 cells, which lack a functional high-affinity transporter, and screening surviving cells for dependence on very high potassium concentrations. The hkr1 phenotype is expressed only in the presence of trk2-1.