Inter- and intra-species comparative analysis of drought effects on seed metabolic composition

Drought stress can severely affect seed characteristics and seed metabolism during development, resulting in a grain yield reduction. Here, we examined the effect of drought on seed characteristics and central metabolism of seven different plant species, i.e., tomato, pepper, and eggplant from the Solanaceae family; melon and watermelon from the Cucurbitaceae family; maize from the Poaceae family; and sunflowers from the Asteraceae family. Synchronized changes of seed weight and seed size in response to drought were observed, showing smaller seed size and lower 1000 seeds weight for tomato and melon while larger seed size and higher 1000 seeds weight for pepper, eggplant, maize, and sunflower. Except for watermelon, number of seeds per plant declined in drought condition for all the species. Principal component analysis and hierarchical clustering highlighted differences of seed relative metabolite content due to phylogenetic differences and different regimes of water deficit. Correlation network analysis revealed interspecies differences in the metabolites associated with seed traits and stress-specific metabolite coordinated behavior in each species. The results suggest that the maintenance of seed dimensions in droughty environments may depend on the rewiring of amino acids and sugar metabolic network. The detected metabolic interactions that are conserved across species shed light on phylogenetic relationships. This comparative study expands our understanding of the interspecific diversity of seed metabolism in response to drought and may assist us for future breeding programs in light of climate change.