title: Nitrogen remobilization and conservation, and underlying senescence-associated gene expression in the perennial switchgrass Panicum virgatum.
abstract: Improving nitrogen (N) remobilization from aboveground to underground organs during yearly shoot senescence is an important goal for sustainable production of switchgrass (Panicum virgatum) as a biofuel crop. Little is known about the genetic control of senescence and N use efficiency in perennial grasses such as switchgrass, which limits our ability to improve the process. Switchgrass aboveground organs (leaves, stems and inflorescences) and underground organs (crowns and roots) were harvested every month over a 3-yr period. Transcriptome analysis was performed to identify genes differentially expressed in various organs during development. Total N content in aboveground organs increased from spring until the end of summer, then decreased concomitant with senescence, while N content in underground organs exhibited an increase roughly matching the decrease in shoot N during fall. Hundreds of senescence-associated genes were identified in leaves and stems. Functional grouping indicated that regulation of transcription and protein degradation play important roles in shoot senescence. Coexpression networks predict important roles for five switchgrass NAC (NAM, ATAF1,2, CUC2) transcription factors (TFs) and other TF family members in orchestrating metabolism of carbohydrates, N and lipids, protein modification/degradation, and transport processes during senescence. This study establishes a molecular basis for understanding and enhancing N remobilization and conservation in switchgrass.
authors.affiliation: Plant Biology Division, the Samuel Roberts Noble Foundation, Ardmore, OK, 73401, USA.|BioEnergy Sciences Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Jiading
authors.initials: J
authors.lastname: Yang
authors.affiliation: Plant Biology Division, the Samuel Roberts Noble Foundation, Ardmore, OK, 73401, USA.|BioEnergy Sciences Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Worley
authors.affiliation: Department of Plant Science, South Dakota State University, Brookings, SD, 57007, USA.
authors.forename: Qin
authors.identifier: 0000-0002-3264-8392
authors.initials: Q
authors.lastname: Ma
authors.affiliation: Plant Biology Division, the Samuel Roberts Noble Foundation, Ardmore, OK, 73401, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Plant Biology Division, the Samuel Roberts Noble Foundation, Ardmore, OK, 73401, USA.
authors.forename: Ivone
authors.initials: I
authors.lastname: Torres-Jerez
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA.
authors.forename: Gaoyang
authors.initials: G
authors.lastname: Li
authors.affiliation: Plant Biology Division, the Samuel Roberts Noble Foundation, Ardmore, OK, 73401, USA.
authors.forename: Patrick X
authors.initials: PX
authors.lastname: Zhao
authors.affiliation: BioEnergy Sciences Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.|Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Plant Biology Division, the Samuel Roberts Noble Foundation, Ardmore, OK, 73401, USA.|BioEnergy Sciences Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Plant Biology Division, the Samuel Roberts Noble Foundation, Ardmore, OK, 73401, USA.|BioEnergy Sciences Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Udvardi
mesh_terms: D018533:Biomass; D018506:Gene Expression Regulation, Plant; D053263:Gene Regulatory Networks; D009584:Nitrogen / Q000378:metabolism*; D008897:Panicum / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D012621:Seasons; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors; D009584:Nitrogen
keywords: gene expression; nitrogen remobilization; senescence; switchgrass (Panicum virgatum); transcription factors