title: Dynamics of biomass partitioning, stem gene expression, cell wall biosynthesis, and sucrose accumulation during development of Sorghum bicolor.
abstract: Biomass accumulated preferentially in leaves of the sweet sorghum Della until floral initiation, then stems until anthesis, followed by panicles until grain maturity, and apical tillers. Sorghum stem RNA-seq transcriptome profiles and composition data were collected for approximately 100 days of development beginning at floral initiation. The analysis identified >200 differentially expressed genes involved in stem growth, cell wall biology, and sucrose accumulation. Genes encoding expansins and xyloglucan endotransglucosylase/hydrolases were differentially expressed in growing stem internodes. Genes encoding enzymes involved in the synthesis of cellulose, lignin, and glucuronoarabinoxylan were expressed at elevated levels in stems until approximately 7 days before anthesis and then down-regulated. CESA genes involved in primary and secondary cell wall synthesis showed different temporal patterns of expression. Following floral initiation, the level of sucrose and other non-structural carbohydrates increased to approximately 50% of the stem's dry weight. Stem sucrose accumulation was inversely correlated with >100-fold down-regulation of SbVIN1, a gene encoding a vacuolar invertase. Accumulation of stem sucrose was also correlated with cessation of leaf and stem growth at anthesis, decreased expression of genes involved in stem cell wall synthesis, and approximately 10-fold lower expression of SbSUS4, a gene encoding sucrose synthase that generates UDP-glucose from sucrose for cell wall biosynthesis. Genes for mixed linkage glucan synthesis (CSLF) and turnover were expressed at high levels in stems throughout development. Overall, the stem transcription profile resource and the genes and regulatory dynamics identified in this study will be useful for engineering sorghum stem composition for improved conversion to biofuels and bio-products.
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77845, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: McKinley
authors.affiliation: Department of Soil and Crop Sciences, Texas A&M University, College Station, TX, 77845, USA.
authors.forename: William
authors.initials: W
authors.lastname: Rooney
authors.affiliation: MSU-DOE laboratory, Michigan State University, East Lansing, MI, 48823, USA.
authors.forename: Curtis
authors.initials: C
authors.lastname: Wilkerson
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77845, USA.
authors.forename: John
authors.initials: J
authors.lastname: Mullet
mesh_terms: D018533:Biomass; D002473:Cell Wall / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism; D045868:Sorghum / Q000254:growth & development* / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*
chemical_list: D013395:Sucrose; D016695:Glycosyltransferases; C473049:xyloglucan - xyloglucosyltransferase
keywords: 
  Sorghum bicolor
  ; bioenergy; cell wall biology; stem sucrose; transcriptome analysis; vacuolar invertase