The first plastid genome for the plant parasite family Cytinaceae

Parasitic plants are a noticeable exception to the evolutionary stability of the plastid genome, but only some parasite lineages have been sequenced so far. Roquet et al. provide the complete plastome of Cytinus hypocistis, the first parasite sequenced for Malvales.

Chloroplast genome map of Cytinus hypocistis showing annotated genes.
Chloroplast genome map of Cytinus hypocistis showing annotated genes. The grey circle indicates the GC content and the line marks the 50 % threshold. Ψ indicates pseudogenes and * indicates genes that might be pseudogenes.

This extremely divergent genome is highly reduced and some regions of this genome are likely to have evolved under relaxed negative selection, suggesting that further plastome reduction is ongoing and linked to the loss of photosynthetic activity. Increased selection intensity and strong positive selection are detected for rpl22 in Cytinus, which might indicate an evolutionary role in the host-parasite coevolution.

Further reading

Cristina Roquet, Éric Coissac, Corinne Cruaud, Martí Boleda, Frédéric Boyer, Adriana Alberti, Ludovic Gielly, Pierre Taberlet, Wilfried Thuiller, Jérémie Van Es, Sébastien Lavergne, 2016, 'Understanding the evolution of holoparasitic plants: the complete plastid genome of the holoparasite Cytinus hypocistis (Cytinaceae)', Annals of Botany, vol. 118, no. 5, pp. 885-896