Journal Article Research Support, U.S. Gov't, Non-P.H.S. Paulinella Research Support, Non-U.S. Gov't Rhizaria endosymbiotic gene transfer photosynthesis photosynthetic eukaryotes primary endosymbiosis Archaeplastida Glaucophyta Letter Photosystem II Protein Complex RNA, Spliced Leader Review Rhodophyta algae algal evolution chromatophore endosymbiosis extremophiles genome reduction light regulation natural selection organellogenesis plastid evolution protein truncation rare species splice leader trans-splicing