Interplay between sulfur nutrition and water stress tolerance in pea : a focus on seed development and composition

International audience; Water stress and sulfur-deficiency are two constraints increasingly faced by crops due to climate change and low-input practices. To investigate their interplay in the grain legume pea (Pisum sativum L.), sulfate was depleted at mid-vegetative stage and a moderate 9-day water stress period was imposed during the early reproductive phase. The combined stress accelerated seed production, lowering yield, one-seed weight and seed number per plant, but rebalanced seed globulin composition. In fact, the moderate water stress mitigated the negative effect of sulfur-deficiency on the accumulation of sulfur-rich globulins in seeds, probably due to a lower seed sink strength for nitrogen, enabling a readjustment of the sulfur-poor/sulfur-rich globulin ratio. These results uncovered the importance of sulfur for stabilizing seed yield in pea facing short and moderate water stress episodes, and showed that the adaptive response of sulfur-deprived plants to water stress is much more complicated than a simple additive response. A transcriptome analysis of developing seeds at the end of the combined stress period clearly advanced our knowledge of the seed response to the single or double stresses. Among the results that will be presented is a specific up-regulation of a set of genes in response to the combined stress, indicating the establishment of unique regulatory processes when sulfur-deficiency is combined with water stress and highlighting candidate genes to fine-tune the regulation of globulin synthesis under stressed conditions.