The development of instabilities and structures in the protostellar
disc can have a significant impact on the dynamics of solids embedded
in the disc and in the process of planetesimal formation. On the one
hand, by producing local pressure maxima, such structures promote the
formation of planetesimals in such agglomeration sites for meter sized
objects. On the other hand, by dynamically stirring up the
planetesimal population, they might induce destructive collisions and
hamper further growth. In this talk I will discuss these issues in
reference to structures produced by gravitational instabilities in the
earliest phases of star formation. I will show that, during this
phase, planetesimals preferentially form in the outer disc, beyond a
few tens of AU, in a ring roughly coincident with the Kuiper belt in
the Solar System. I will then discuss the implications of such model
in relation to some observed properties of protostellar and debris
discs.  Finally, I will present synthetic ALMA images of
self-gravitating protostellar discs, whose physical properties are
derived from numerical simulations, in order to discuss whether these
kind of structures might or might not be detectable in the near
future.