Formyl group modification of chlorophyll a: a major evolutionary mechanism in oxygenic photosynthesis

ABSTRACT We discuss recent advances in chlorophyll research in the context of chlorophyll evolution and conclude that some derivations of the formyl side chain arrangement of the porphyrin ring from that of the Chl a macrocycle can extend the photosynthetic active radiation (PAR) of these molecules, for example, Chl d and Chl f absorb light in the near‐infrared region, up to ∼750 nm. Derivations such as this confer a selective advantage in particular niches and may, therefore, be beneficial for photosynthetic organisms thriving in light environments with particular light signatures, such as red‐ and near‐far‐red light‐enriched niches. Modelling of formyl side chain substitutions of Chl a revealed yet unidentified but theoretically possible Chls with a distinct shift of light absorption properties when compared to Chl a. The present work builds on recent findings on the biosynthetic pathway of chlorophyll (Chl) d and what is known of the biosynthesis of other chlorophylls. The likely evolution of Chls is discussed especially in the light of the recently discovered Chls d and f. The work suggests an evolutionary explanation for the currently known diversity of Chls and suggests that more Chls could be discovered in the future.