Transplantation and subsequent behavior of mitochondria in cells of Phytophthora

Abstract

Mitochondria isolated from streptomycin-resistant (Sr) protoplasts of Phytophthora parasitica were transferred into chloramphenicol-resistant (Cpr) protoplasts of P. parasitica or Phytophthora capsici with an average successful rate of 1.7 × 10-4, using a selective medium containing streptomycin. No colonies appeared when self-fusion products of donor mitochondria or recipient protoplasts were exposed to the selective medium. Mitochondria isolated from Cpr protoplasts of P. capsici were also transferred into Sr protoplasts of P. parasitica with a similar success rate using a selective medium containing chloramphenicol. Zoospores produced by the Cpr+Sr intraspecific mitochondrial hybrid gave rise to Sr and Cpr+Sr cultures. The second generation zoospores produced by Sr and Cpr+Sr cultures also gave rise to Sr and Cpr+Sr cultures, suggesting the possible occurrence of fusion between some of the Cpr mitochondria and Sr mitochondria, and the displacement of non-fused Cpr mitochondria in the receptor protoplast by the donor Sr mitochondria. Zoospores produced by the interspecific mitochondrial hybrid gave rise to Cpr, Sr, Cpr+Sr, and Cps +Ss cultures. The second generation zoospores produced by Cpr+Sr or Sr cultures also gave rise to the same four types of cultures, suggesting the existence of residual antibiotic-sensitive mitochondria (Cps+Ss) in the parental isolates and the random distribution of Cpr, Sr, and Cps+Ss mitochondria during asexual reproduction. Results suggest that the phenotype of antibiotic resistance / sensitivity was the end result of the interactions among the three types of mitochondria.Key words: mitochondrial transplantation, mitochondrial hybrid, antibiotic resistance, Phytophthora parasitica, Phytophthora capsici.