Ludwig Maximilian University of Munich Munich, Bayern, Germany
Body of Abstract: C4 and CAM photosynthesis are carbon-concentration mechanisms that allow plants to thrive in hot and dry environments. Introducing C4 or CAM traits in C3 species are long-term goals for crop improvement. Gene expression analyses and metabolite profiling is rarely combined, although it provides a more comprehensive understanding of metabolic pathways such as C4 or CAM. Species of Sesuvioideae exhibit photosynthetic variability including various C4 and CAM phenotypes, and are therefore a suitable study group for CAM and C4 evolution. Gene expression analysis of C3Sesuvium portulacastrum showed a number of up-regulated key C4 genes. We have now profiled 81 metabolites in cotyledons and leaves of C4-like S. sesuvioides and leaves of C3S. portulacastrum. We found that the accumulation of some C4-related metabolites such as aspartate was higher in the C3 species. In addition, the concentrations of malic and oxalic acids did not differ significantly between C3 and C4-like species. Furthermore, we found a significant accumulation of proline and glutamate, both essential amino acids for stress tolerance in C3 species. Our results indicate that S. portulacastrum does not operate a typical C3 metabolism, but a C4-like photosynthetic type that differs from the type shown by its relative S. sesuvioides.