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.

Identification, Characterization, and Expression Analysis of Cell Wall Related Genes in Sorghum bicolor (L.) Moench, a Food, Fodder, and Biofuel Crop

“…and among the cell types within a tissue (i.e., epidermal, xylem, phloem, fiber cells, etc. ; Hatfield et al, 1999; McKinley et al, 2016). Expression analysis across different tissues will provide important insight into the role of cell wall related genes in that particular tissue.…”

“…This analysis provides information on the tissue specific target genes for bioengineering purposes. A recent study of sorghum gene expression in pre- and post-anthesis stages of stem internodes showed differential expression of genes involved in growth, cell wall development and stem sugar accumulation (McKinley et al, 2016). CesA, Csls, callose synthases, XTHs, glucuroarabinoxylan biosynthetic genes, expansins, glucosyl hydrolases, pectin lyases/esterases, and lignin biosynthetic genes were among the major differentially expressed cell wall related genes (McKinley et al, 2016).…”

“…Characterization of sorghum (1,3; 1,4)-β-glucan biosynthetic gene subfamilies CslF and CslH showed that CslF6 plays an important role in elongating cells while CslH3 has a major role in cells that has stopped growth and started depositing storage compounds (Ermawar et al, 2015a). In a recent study, genes encoding cellulose, lignin, and glucuroarabinoxylan biosynthetic enzymes were dynamically expressed during the different development stages of sorghum (McKinley et al, 2016). The expansins and XTHs encoding genes were also shown to be differentially expressed in the growing stem internodes of sorghum.…”

Characterization of sugar metabolism in the stem of Tachisuzuka, a whole-crop silage rice cultivar with high sugar content in the stem

“…Some studies suggest that high-sugar varieties of sugarcane and sweet sorghum are characterized by high SPS activity and low VIN activity (Liu et al, 2013;McKinley et al, 2016;Zhu et al, 1997). However, this is not applicable to TS, because SPS activity and gene expression levels in leaf sheaths did not differ significantly between TS and KH (Figures 4 and 5).…”

“…and sweet sorghum (Sorghum bicolor), which mainly accumulate soluble sugars in the stem (for reviews, see Bihmidine et al, 2013;Slewinski, 2012;Wang et al, 2013). Those studies identified key enzymes and transporters for sugar accumulation, such as sucrose-phosphate synthase (Botha & Black, 2000;Grof et al, 2007;Liu et al, 2013;Zhu et al, 1997), vacuolar acid invertase (Liu et al, 2013;McKinley et al, 2016;Zhu et al, 1997), and tonoplast sugar transporter (Bihmidine et al, 2016). However, sugar metabolism in rice stems has received less attention.…”