PNNL

Abstract

Drought is the most important environmental stress limiting crop yields. The C4 cereal, Sorghum bicolor, is a critical food, forage, and emerging bioenergy crop that is notably drought-tolerant. We conducted a large-scale field experiment, imposing pre- and post-flowering drought stress on two genotypes of S. bicolor across a tightly-resolved time series, resulting in a data set of over 350 transcriptomes. We observed a fast and global transcriptomic response in leaf and root tissues with clear temporal patterns, including modulation of well-known drought pathways. We identified genotypic differences in core photosynthesis and reactive oxygen species scavenging pathways, highlighting possible mechanisms of drought tolerance and of the delayed senescence, stay-green phenotype. Finally, we discovered a large scale depletion in the expression of genes critical to arbuscular mycorrhizal (AM) symbiosis, with a corresponding drop in AM fungal mass in the plants’ rhizosphere.