Evolution from the prokaryotic to the higher plant chloroplast signal recognition particle: the signal recognition particle RNA is conserved in plastids of a wide range of photosynthetic organisms.

The protein targeting signal recognition particle (SRP) pathway in chloroplasts of higher plants has undergone dramatic evolutionary changes. It disposed of its RNA, which is an essential SRP component in bacteria, and uses a unique chloroplast-specific protein cpSRP43. Nevertheless, homologs of the conserved SRP54 and the SRP receptor, FtsY, are present in higher plant chloroplasts.