Should I stay or should I go? Retention and loss of components in vestigial endosymbiotic organelles.

Our knowledge on the variability of the reduced forms of endosymbiotic organelles - mitochondria and plastids - is expanding rapidly, thanks to growing interest in peculiar microbial eukaryotes, along with the availability of the methods used in modern genomics and transcriptomics. The aim of this work is to highlight the most recent advances in understanding these organelles' diversity, physiology and evolution. We also outline the known mechanisms behind the convergence of traits between organelles which have undergone reduction independently, the importance of the earliest evolutionary events in determining the vestigial organelles' eventual fate, and a proposed classification of nonphotosynthetic plastids.