Читать книгу Algorithms in Bioinformatics - Paul A. Gagniuc - Страница 66

Chromatophores are photosynthetic organelles discovered in species of freshwater amoeboids from Paulinella genus. Evidence shows that primary endosymbiosis of chromatophores occurred relatively recently (90–140 million years ago) compared to the origin of canonical Archaeplastida plastids (>1.5 billion years ago) [192]. Paulinella lineage gained the chromatophores independently. Thus, chromatophores are considered a valuable model for recent endosymbiosis and a perfect example of organellogenesis. The chromatophore genome is 1 Mb in length and encompasses ∼800 protein-coding genes [193]. A uniformity exists between the genome size of different organelles, except for chromatophores (Table 2.2). Synechococcus (WH5701) is a unicellular cyanobacterium found in the marine environment and the closest relative of the chromatophore. Bioinformatic evidence shows that chromatophores experienced a genome reduction compared to Synechococcus, from which about 74% of the genes were lost. Consequently, these reductions led to the loss of essential functions and made the chromatophore totally dependent on the host for growth and survival [193].