1-05: Uncovering switchgrass crown and rhizome metabolism in latitudinally differentiated ecotypes

Switchgrass (Panicum virgatum L.) is being developed as a perennial biomass energy crop for temperate regions of the USA.  To optimize biomass yields, southern ecotypes with longer growing season are developed for use in northern latitudes and in some years have poor winter survival. Here, we evaluate the crown and rhizome metabolism of two contrasting tetraploid populations of switchgrass: cv. Kanlow, a southern lowland ecotype, with cv. Summer, a northern upland ecotype when grown at the same latitude.  These populations differed significantly with respect to maturity, yield, and winter survival.  Comparisons were made post-flowering to understand cellular metabolism as the plants transition to winter dormancy.  Significant differences existed in transcript abundances for 9561 genes, including nutrient transporters, WRKY transcription factors and defense proteins.  Principal component analysis (PCA) clearly differentiated between both the Summer and Kanlow transcriptomes and metabolomes.  Gene-set enrichment analyses showed that a number of pathways were differentially up-regulated in the two cultivars.  For both populations, protein levels and enzyme activities agreed well with transcript abundances for genes involved in the phenylpropanoid pathway which was up-regulated in Kanlow crowns and rhizomes.  For Summer plants, key events included changes in cellular redox status and metabolic redirection, potentially as an integrated response to loss in photosynthate and environmental cues such as shorter days and cooler nights.  These results led to the analyses of the crown and rhizome transcriptomes at additional harvest times and some initial results from this data set will also be discussed.