| Abstract: | Carotenoid compositions were analyzed for ten strains of Nephroselmis (Prasinophyceae) containing four described and three undescribed species. Based on the distribution pattern of the siphonaxanthin series, five carotenoid types were recognized in the examined strains/species: type I (N. astigmatica Inouye et Pienaar, N. pyriformis (N. Carter) Ettl, and Nephroselmis sp1. MBIC 11158) had siphonaxanthin C12:1 and C14:1 esters as well as 6′‐OH siphonaxanthin C12:1 and C14:1 esters, type II (Nephroselmis sp2. MBIC 11149) had siphonaxanthin C8:1 ester, type III (Nephroselmis sp3. NIES 486, NIES‐PS 535, and MBIC 10871) had 19‐methoxy siphonaxanthin and siphonaxanthin C12:1 and C14:1 esters, type IV (N. spinosa Suda) had only a small amount of siphonaxanthin C12:1 ester, and type V (N. olivacea Stein) had lutein as a major carotenoid but completely lacked the siphonaxanthin series. 19‐Methoxy siphonaxanthin was a novel and very unique carotenoid, that is, it contains a methoxy group and was found for the first time in photosynthetic eukaryotes. Additionally, carotenoids containing a primary methoxy group had previously never been found in any group of organisms. Siphonaxanthin C8:1 ester, which was only known as a trace carotenoid in Chlamydomonas parkeae Ettl, was first discovered as a major carotenoid in Nephroselmis sp2. (MBIC 11149). Based on these results and comparison of the phylogenetic relationships of the Nephroselmis species used, we discuss the taxonomic significance of the carotenoid types and evolutionary process of the photosynthetic antenna systems in green plants. |
