Photosynthetic Pigment Composition In The Primitive Green Alga Mesostigma Viride (Prasinophyceae): Phylogenetic And Evolutionary Implications

The photosynthetic pigment composition of Mesostigma viride Lauterborn, a primitive green alga, was determined. This alga contained chl a and b , lycopene, lutein, siphonaxanthin, gamma-carotene, beta-carotene, antheraxanthin, violaxanthin, neoxanthin, and two novel carotenoid fatty acid esters, siphonaxanthin C12:0 ester and siphonaxanthin C14:0 ester. The esters were saturated, whereas all previously identified siphonaxanthin and loroxanthin esters have been mono-unsaturated (trans -Delta2). Neoxanthin was the all-trans form. This is the first such case detected in the chloroplasts of green plants. The 9'-cis form of neoxanthin is believed to be universally present in the chloroplasts of green plants (Streptophyta and Chlorophyta) and is a precursor of abscisic acid. However, the 9'-cis form was not found in M. viride. Based on these results, we discuss the phylogenetic implications and early evolution of the antenna pigment system in green plants.