Cooperation is Fleeting in the World of Transposable Elements
Figure 1
Selfish and Cooperative Transposition, and the Game ISs Play
(A) shows the basic structure of a composite transposon. The narrow open bar indicates the selectable gene(s). The wide bar inscribed with ISL and ISR indicates the ISs flanking these genes. Gray triangles indicate the inverted repeats that constitute the inside and outside ends of the ISs. Red triangles indicate repeat sequences used in a particular type of transposition event. The upper panel illustrates selfish transposition, where either IS transposes independently from the other. The lower panel illustrates cooperative transposition, where the composite transposes as a whole, taking the selectable genes with it.
(B) The structure of the payoff matrix P describing the payoff to ISL in the symmetric game, where both ISs have the same target specificity and the same likelihood of undergoing DNA rearrangement. The parameter t is the joint probability of transposition and horizontal transfer of the transposition product, r is the probability of DNA rearrangement associated with cooperative transposition, and s is the probability that the new host of a transposable element will need the selectable genes for its survival. Entry PSC is the payoff to ISL if a selfish ISL is paired with a cooperative ISR in a composite, and analogously for the other entries of P. The payoff matrix for ISR is the transpose of P.
(C) Schematic diagram of the evolutionary stable strategies (ESSs) in the case of genetic dominance of selfish transposition. Selfish transposition (“S”) is the only ESS if r > ts. Selfish and cooperative transposition (“C”) are both ESSs if r < ts.