Figure 5.

Model of the involvement of nt-RecA in DSB repair in somatic plant cells. Exonucleases process the DSB in the acceptor molecule to produce 3′ single-stranded overhangs (a). A free 3′-end invades the double-stranded donor forming a D-loop, and repair synthesis commences (b). The invading end of the single strand is blocked by replication (c). The intermediate is processed further, and the break is sealed either by homologous (“two-sided,” d and e) or by illegitimate recombination (“one-sided,” f and g). Free single-stranded DNA is generated by replacement of one of the strands of the acceptor molecule during DNA synthesis that can act as a substrate for nt-RecA (d). nt-RecA promotes strand exchange with the homologous strand, and the break is sealed via homologous recombination at both ends (e). In contrast, in the absence of nt-RecA, the enzymatic machinery promoting illegitimate recombination present in somatic plant cells dominates, single strands are not paired or abandoned (f), and the break is sealed via illegitimate recombination (g).