Transcriptomic and metabolomic responses of the nodulated pea root system during rewatering

In pea (Pisum sativum), as in other legumes, nitrogen nutrition relies on two different sources: soil mineral nitrogen supply via roots and and symbiotic atmospheric N2 fixation within root nodules. However symbiotic nitrogen fixation is very sensitive to abiotic stresses, especially drought, which is becoming increasingly frequent in the current context of climate change. Although the ability of a crop to recover after a drought period can determine both its survival and its yield at harvest, little is known about the physiological and molecular mechanisms occurring during recovery. In this work, we aimed at characterizing the kinetics of growth and nitrogen acquisition recovery after water stress, and at identifying the dynamics of the molecular adjustment mechanisms occurring in roots and nodules. For this purpose, two pea genotypes with contrasting nodulated root system architecture and recovery strategies were grown in the 4PMI phenotyping platform (Dijon). Plants were subjected to a two-week water stress period during the vegetative stage, followed by two weeks of optimal re-watering. For each genotype, roots and nodules were collected at the end of the drought period, and at 4 time points during recovery, and subjected to transcriptomics (RNA-seq) and metabolomics (GC-MS) analyses. The results highlight common and specific molecular processes occurring for each genotype. The implication of these processes in the molecular reprogramming taking place during recovery period will be discussed.