Gene Expression and Physiological Differences in Neo-Octoploid Switchgrass Subjected to Drought Stress

Switchgrass (Panicum virgatum L.) has been subject to breeding to improve its yield and composition for bioenergy, but improving its tolerance to environmental variability is just beginning. Different ploidy populations act as somewhat distinct gene pools which can only be bridged through whole genome reduction or duplication events. In order to document potential wide-ranging effects of whole genome duplication, we examined the effects of water stress on growth, physiology, and gene expression in individual tetraploid clones of the switchgrass cultivar ‘Liberty’ as well as neo-octoploid lines derived from it. The neo-octoploids behaved similarly to Liberty under water-stress and recovery conditions. Growth rates, photosynthesis, gas exchange, node numbers, and height were reduced in plants under water stress while proline levels were increased. A total of 6134 differentially expressed genes (8% of the annotated genes with detectable expression in crown tissue) were detected under water deficit stress, while 3310 differentially expressed genes were detected in crown tissue after 1 week of recovery from water deficit stress relative to well-watered treatments. Only a small number of genes were identified as being differentially expressed between 4x Liberty and its 8x derivatives. Overall design: mRNA profiles of crown tissue from related individuals and cultivars were sampled after water-stress and during a recovery period. Paired-end sequencing of mRNA was performed using Illumina.