Apicoplast and mitochondrion in gametocytogenesis of Plasmodium falciparum

Abstract

Live cell imaging of human malaria parasites Plasmodium falciparum during gametocytogenesis revealed that the apicoplast does not grow, whereas the mitochondrion undergoes remarkable morphological development. A close connection of the two organelles is consistently maintained. The apicoplast and mitochondrion are not components of the male gametes, suggesting maternal inheritance.

FIG. 1.

Live cell images of 3D7 ACP(L):mOrange-CS(L):GFPmut2 gametocytes at stage II (a and b) and stage III (c to f), showing a small apicoplast (red) that is always encased by the mitochondrion (green). At stage III, the apicoplast is round (c and e) or slightly elongated (d and f). In contrast, the mitochondrion forms branches from the cluster that encase the apicoplast. Sometimes the GFP labeling for the mitochondrion is heterologous, but continuous (c and d). Scale bars, 3 μm.

FIG. 2.

Live cell images of 3D7 ACP(L):mOrange-CS(L):GFPmut2, at stage IV (a and b) and stage V (c and d), showing the apicoplast (red) and mitochondrion (green) association in macrogametocytes (a and c) and microgametocytes (b and d). The apicoplast (red) does not elongate or branch but stays small. Often, the mOrange signal for the apicoplast is weak in the mature microgametocyte (d). Scale bars, 3 μm.

FIG. 3.

Exflagellated microgametes. Immunofluorescence images of the mitochondrion in NF54 parasites, fixed 7 min (a and b) or 30 min (c to f) after exflagellation induction. (a to d) The mitochondrion (labeled with the anti-Hsp60 antibody [green]) stays single even after each microgamete (whose axoneme is labeled with the anti-alpha tubulin antibody [red]) is formed (a and b) and exflagellated (c and d). (e and f) The apicoplast (labeled with the anti-ACP antibody [green]) stays single and does not enter the exflagellated microgametes (whose axoneme is labeled with the anti-alpha tubulin antibody [red]). Scale bars, 3 μm.