TY - JOUR
T1 - Transcriptomic analysis reveals evidence for a cryptic plastid in the colpodellid Voromonas pontica, a close relative of chromerids and apicomplexan parasites
AU - Gile, Gillian H.
AU - Slamovits, Claudio H.
PY - 2014/5/5
Y1 - 2014/5/5
N2 - Colpodellids are free-living, predatory flagellates, but their close relationship to photosynthetic chromerids and plastidbearing apicomplexan parasites suggests they were ancestrally photosynthetic. Colpodellids may therefore retain a cryptic plastid, or they may have lost their plastids entirely, like the apicomplexan Cryptosporidium. To find out, we generated transcriptomic data from Voromonas pontica ATCC 50640 and searched for homologs of genes encoding proteins known to function in the apicoplast, the non-photosynthetic plastid of apicomplexans. We found candidate genes from multiple plastid-associated pathways including iron-sulfur cluster assembly, isoprenoid biosynthesis, and tetrapyrrole biosynthesis, along with a plastid-type phosphate transporter gene. Four of these sequences include the 5′ end of the coding region and are predicted to encode a signal peptide and a transit peptide-like region. This is highly suggestive of targeting to a cryptic plastid. We also performed a taxon-rich phylogenetic analysis of small subunit ribosomal RNA sequences from colpodellids and their relatives, which suggests that photosynthesis was lost more than once in colpodellids, and independently in V. pontica and apicomplexans. Colpodellids therefore represent a valuable source of comparative data for understanding the process of plastid reduction in humanity's most deadly parasite.
AB - Colpodellids are free-living, predatory flagellates, but their close relationship to photosynthetic chromerids and plastidbearing apicomplexan parasites suggests they were ancestrally photosynthetic. Colpodellids may therefore retain a cryptic plastid, or they may have lost their plastids entirely, like the apicomplexan Cryptosporidium. To find out, we generated transcriptomic data from Voromonas pontica ATCC 50640 and searched for homologs of genes encoding proteins known to function in the apicoplast, the non-photosynthetic plastid of apicomplexans. We found candidate genes from multiple plastid-associated pathways including iron-sulfur cluster assembly, isoprenoid biosynthesis, and tetrapyrrole biosynthesis, along with a plastid-type phosphate transporter gene. Four of these sequences include the 5′ end of the coding region and are predicted to encode a signal peptide and a transit peptide-like region. This is highly suggestive of targeting to a cryptic plastid. We also performed a taxon-rich phylogenetic analysis of small subunit ribosomal RNA sequences from colpodellids and their relatives, which suggests that photosynthesis was lost more than once in colpodellids, and independently in V. pontica and apicomplexans. Colpodellids therefore represent a valuable source of comparative data for understanding the process of plastid reduction in humanity's most deadly parasite.
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U2 - 10.1371/journal.pone.0096258
DO - 10.1371/journal.pone.0096258
M3 - Article
C2 - 24797661
AN - SCOPUS:84900402320
SN - 1932-6203
VL - 9
JO - PloS one
JF - PloS one
IS - 5
M1 - e96258
ER -