Meeting Abstract
By far, the largest numbers of formerly photosynthetic parasites are found among the red algae. Nearly half the floridiophyte orders in the red algae contain parasitic taxa and there appear to be nearly a hundred independent parasite lineages within the group. Because there are so many independent evolutionary events of parasitism in the red algae and it appears that parasites have most often evolved from a common ancestor of their hosts, this is an intriguing group to explore the evolutionary changes concomitant with a transition from a free-living to parasitic lifestyle. For much of their life history many red algal parasites exist as a nucleus and a collection of mitochondria freely intermingling with the host’s organelles and cytoplasm within host cells. As the first step in understanding how the parasite relationship has repeatedly evolved in the red algae and why parasites are so well tolerated as intracellular guests, we have sequenced the genome of the free-living red seaweed Gracilariopsis andersonii and Gracilariophila oryzoides, its obligate parasite with a combination of Illumina and PacBio sequencing. Their gene repertoire and synteny suggests that successful parasitic association among red algae results from similarity rather than evading host detection as is common among most other parasitic lineages.
