Seasonal below‐ground metabolism in switchgrass

• Published in: The Plant journal : for cell and molecular biology 2017-12, Vol.92 (6), p.1059-1075
• Main Authors: Palmer, Nathan A., Saathoff, Aaron J., Scully, Erin D., Tobias, Christian M., Twigg, Paul, Madhavan, Soundararajan, Schmer, Marty, Cahoon, Rebecca, Sattler, Scott E., Edmé, Serge J., Mitchell, Robert B., Sarath, Gautam
• Format: Article
• Language: English
• Subjects: Abscisic acid; Abscisic Acid - metabolism; Accession numbers: SRX1601466; Annual variations; autophagy; Biofuels; Biomass; Carbon dioxide; Cascades; Chromosome Mapping; Dehydration; Dormancy; Energy transduction; Gene expression; Information processing; Metabolic pathways; Metabolism; Metabolites; Mitochondria; Oxidative phosphorylation; Panicum - genetics; Panicum - growth & development; Panicum - metabolism; Panicum virgatum; Phosphorylation; Plant Growth Regulators - metabolism; Plants (botany); Polyploidy; Rapamycin; Rhizome - genetics; Rhizome - growth & development; Rhizome - metabolism; Rhizomes; Seasonal variations; Seasons; Sequence Analysis, RNA; Signal transduction; Signaling; Substrates; Sucrose; Sugar; Survival; switchgrass; Synthesis; target of rapamycin kinase; Tissues; TOR protein; Transcription; Transcriptome; transcriptomes; Winter
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.13742

Summary Switchgrass (Panicum virgatum), a perennial, polyploid, C4 warm‐season grass is among the foremost herbaceous species being advanced as a source of biomass for biofuel end uses. At the end of every growing season, the aerial tissues senesce, and the below‐ground rhizomes become dormant. Future growth is dependent on the successful over‐wintering of the rhizomes. Although the importance of rhizome health to overall year‐upon‐year plant productivity has been long recognized, there is limited information on seasonal changes occurring during dormancy at both the transcriptome and metabolite levels. Here, global changes in transcriptomes and metabolites were investigated over two growing seasons in rhizomes harvested from field‐grown plants. The objectives were: (a) synthesize information on cellular processes that lead to dormancy; and (b) provide models that could account for major metabolic pathways present in dormant switchgrass rhizomes. Overall, metabolism during dormancy appeared to involve discrete but interrelated events. One was a response to abscisic acid that resulted in dehydration, increases in osmolytes and upregulation of autophagic processes, likely through the target of rapamycin complex and sucrose non‐fermentative‐related kinase‐based signaling cascades. Another was a recalibration of energy transduction through apparent reductions in mitochondrial oxidative phosphorylation, increases in substrate level generation of ATP and reducing equivalents, and recycling of N and possibly CO2 through refixation. Lastly, transcript abundances indicated that cold‐related signaling was also occurring. Altogether, these data provide a detailed overview of rhizome metabolism, especially during dormancy, which can be exploited in the future to improve winter survival in switchgrass. Significance Statement This research synthesizes information on cellular processes that regulate seasonal metabolism of switchgrass rhizomes and provide models for explaining the major metabolic pathways involved in dormancy. This detailed overview of rhizome metabolism provides mechanistic information that can be used to improve winter survival in switchgrass.