Effects of Abiotic Stress on Physiological Plasticity and Water Use of Setaria viridis.

The emerging model Setaria viridis with its C4 photosynthesis and its adaptation to hot and dry locations is a promising system to investigate water use and abiotic stress tolerance. We investigated the physiological plasticity of six S. viridis natural accessions that originated from different regions of the world under normal conditions and conditions of water-deficit stress and high temperatures. Accessions  Zha-1, A10.1 and Ula-1 showed significantly higher of leaf water potential (Ψ_leaf), photosynthesis (A), transpiration (E), and stomatal conductance (g_s) rates as compared Ast-1, Aba-1 and Sha-1 when grown under stress conditions. Expression analysis of genes associated with C4 photosynthesis, aquaporins, ABA biosynthesis and signaling genes including genes involved in stress revealed an increased stress sensitivity of Ast-1, Aba-1 and Sha-1. Gene expression analyses data correlated well with physiological and biochemical activities mediated by the products of the genes under study. Correlation analysis characterized A10.1 and Ast-1  as two extreme tolerant and sensitive accessions originated from United States and Azerbaijan under water-deficit and heat stress, respectively.  Although preliminary, our study demonstrated the plasticity of S. viridis accessions under stress, and allow the identification of tolerant and sensitive accessions that could be use for the study of the mechanisms associated with stress tolerance in C4 grasses and the characterization of the regulatory networks involved