A shared genetic mechanism for melanotic encapsulation of CM-Sephadex beads and a malaria parasite, Plasmodium cynomolgiB, in the mosquito, Anopheles gambiae

A Plasmodium-refractory strain of Anopheles gambiae that melanizes ookinetes and intrathoracically inoculated CM-Sephadex beads was mated to a Plasmodium-susceptible strain that does not melanize the parasite or the beads. The F-1 progeny were then backcrossed to the susceptible strain. Backcross progeny were given a blood meal containing infective Plasmodium cynomolgi B, and the parasites were allowed to develop for 6-7 days, at which time the infected mosquitoes were injected with CM-Sephadex beads. The next day the mosquitoes were dissected and the beads were scored for degree of melanization while the parasites were scored for degree of encapsulation. A Spearman rank order correlation rest of the degree of correlation between the bead melanization phenotype and the parasite encapsulation phenotype gave a correlation coefficient of 0.74 (P < 0.01). This strong correlation between the two melanization responses suggests that the mechanisms for differential bead and parasite melanization of these two mosquito strains share at least one major gene. (C) 1996 Academic Press, Inc.