Carbon concentrating mechanisms in pods are key elements for terminal drought resistance in Phaseolus vulgaris L.

Common bean (Phaseolus vulgaris L.) is one of the most consumed legumes in the human diet. A major problem for this rainfed crop is the decrease in grain yield caused by prolonged drought periods during the reproductive stage of plant development (terminal drought, TD). Despite the importance of the common bean as a substantial source of proteins, TD remains a prevailing threat to the farming of this staple, with losses reaching more than 80%. Based on the high correlation between the common bean resistance to TD with an efficient photo-assimilate mobilization and biomass accumulation in seeds, we aimed to identify mechanisms implicated in its resistance to this stress. We used two representative Durango race common bean cultivars with contrasting yields under TD, grown under well-watered or TD conditions. By comparative transcriptomic analysis focused on source leaves, pods, and seeds from both cultivars, we provide evidence indicating that under TD the resistant cultivar promotes the buildup of transcripts involved in recycling carbon through photosynthesis, photorespiration, and CO2 concentrating mechanisms in pod walls; while in seeds, the induced transcripts participate in sink strength and respiration. Physiological data support this conclusion, implicating their relevance as key processes in the plant response to TD.