Metabolic Background, Not Photosynthetic Physiology, Determines Drought and Drought Recovery Responses in C3 and C2 Moricandias.

Distinct photosynthetic physiologies are found within the Moricandia genus, both C3-type and C2-type representatives being known. As C2-physiology is an adaptation to drier environments, a study of physiology, biochemistry and transcriptomics was conducted to investigate whether plants with C2-physiology are more tolerant of low water availability and recover better from drought. Our data on Moricandia moricandioides (Mmo, C3), M. arvensis (Mav, C2) and M. suffruticosa (Msu, C2) show that C3 and C2-type Moricandias are metabolically distinct under all conditions tested (well-watered, severe drought, early drought recovery). Photosynthetic activity was found to be largely dependent upon the stomatal opening. The C2-type M. arvensis was able to secure 25-50% of photosynthesis under severe drought as compared to the C3-type M. moricandioides. Nevertheless, the C2-physiology does not seem to play a central role in M. arvensis drought responses and drought recovery. Instead, our biochemical data indicated metabolic differences in carbon and redox-related metabolism under the examined conditions. The cell wall dynamics and glucosinolate metabolism regulations were found to be major discriminators between M. arvensis and M. moricandioides at the transcription level.