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Contrasting metabolism in perenniating structures of upland and lowland switchgrass plants late in the growing season

Nathan A. Palmer, Aaron J. Saathoff, Christian M. Tobias, Paul Twigg, Yuannan Xia, Kenneth P. Vogel, Soundararajan Madhavan, Scott E. Sattler, Gautam Sarath
PLoS one 2014 v.9 no. pp. 1-11
Panicum virgatum, acetyl coenzyme A, dormancy, ecotypes, energy crops, enzyme activity, gene expression, gene expression regulation, genes, growing season, indigenous species, messenger RNA, metabolism, metabolites, night temperature, overwintering, phenylpropanoids, photoperiod, plant physiology, plant proteins, principal component analysis, rhizomes, root crown, spring, temperate zones, tetraploidy, transcription factors, transcriptome, transcriptomics, transporters, winter
Switchgrass (Panicum virgatum L.) is a perennial grass native to the USA that is being developed as a bioenergy crop for temperate regions of the world. Its ability to survive winters and produce new growth the following spring is an essential factor of its value as an energy crop. We have explored crown and rhizome metabolism of two contrasting tetraploid populations of switchgrass, cv Kanlow, a lowland ecotype with high yields but poor winter survival, and cv Summer, an upland ecotype with lower yields and excellent, higher winter survival 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 a large specific class of proteins (NB-ARC domain) involved in defense. Principal component analysis (PCA) differentiated between Summer and Kanlow transcriptomes. PCA of metabolites identified by GCMS supported the transcriptomic data, and again differentiated the Kanlow and Summer metabolomes. Gene-set enrichment analyses, showed that a number of pathways were differentially up-regulated in the two ecotypes. 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 appear to be changes in cellular redox status and metabolic redirection with acetyl-CoA as a hub in Summer plants, potentially as an integrated response to loss in photosynthate and environmental cues (short days and cooler nights).