Figure 7. Diagrammatic representation of possible regulation of motility by cAMP mediated wave reversal in L. donovani promastigotes.

A cAMP-dependent signal transduction cascade is triggered when the flagella of a forward swimming parasite encounters any signal(s)/cue(s) (e.g. physical obstruction or osmotic/chemical gradient). The elevated cAMP levels allow the base-to-tip ciliary beating to take over tip-to-base flagellar beating. Ciliary beating allows the cell to alter its direction, after which tip-to-base beating is restarted. Solid arrows denote direction of swimming. Dotted arrows denote direction of wave propagation of flagella. Dotted outline of Leishmania denotes previous position. Filled outline of Leishmania denotes current position.