Published in:
Evolution, 65 (2011) 3, Seite 643-660
Language:
English
ISSN:
1558-5646;
0014-3820
Origination:
Footnote:
Description:
C₄ photosynthesis is a series of biochemical and structural modifications to C₃ photosynthesis that has evolved numerous times in flowering plants, despite requiring modification of up to hundreds of genes. To study the origin of C₄ photosynthesis, we reconstructed and dated the phylogeny of Molluginaceae, and identified C₄ taxa in the family. Two C₄ species, and three clades with traits intermediate between C₃ and C₄ plants were observed in Molluginaceae. C₃-C₄ intermediacy evolved at least twice, and in at least one lineage was maintained for several million years. Analyses of the genes for phosphoenolpyruvate carboxylase, a key C₄ enzyme, indicate two independent origins of fully developed C₄ photosynthesis in the past 10 million years, both within what was previously classified as a single species, Mollugo cerviana. The propensity of Molluginaceae to evolve C₃-C₄ and C₄ photosynthesis is likely due to several traits that acted as developmental enablers. Enlarged bundle sheath cells predisposed some lineages for the evolution of C₃-C₄ intermediacy and the C₄ biochemistry emerged via co-option of photorespiratory recycling in C₃-C₄ intermediates. These evolutionarily stable transitional stages likely increased the evolvability of C₄ photosynthesis under selection environments brought on by climate and atmospheric change in recent geological time.