The leap from aquatic to terrestrial life was a turning point in plant evolution, but how early plants evolved to adapt to life on land remains poorly understood. A recent collaborative study published in Mol Biol Evol explored this mystery by examining the evolution and function of Shikimate Kinase-Like 1 (SKL1), a gene critical for chloroplast development.
While SKL1 was known to influence chloroplast biogenesis in Arabidopsis thaliana, its role in more ancient plant species remained unclear. This study fills that gap by examining SKL1 in Marchantia polymorpha, an early-diverging land plant. The authors show that disrupting SKL1 in Marchantia leads to pigment defects and abnormal chloroplast structures, similar to phenotypes seen in Arabidopsis. Interestingly, SKL1 does not retain the enzymatic activity of its ancestor, shikimate kinase (SK). Instead, it has evolved a novel role, likely a result of structural changes in its substrate-binding pocket. This discovery suggests that SKL1 emerged around the time plants first migrated on land, acquiring a new function essential for chloroplast formation.