Distribution, structure and biosynthetic gene families of (1,3;1,4)‐β‐glucan in Sorghum bicolor

Abstract

In cereals, the presence of soluble polysaccharides including (1,3;1,4)-b-glucan has downstream implications for human health, animal feed and biofuel applications. Sorghum bicolor (L.) Moench is a versatile crop, but there are limited reports regarding the content of such soluble polysaccharides. Here, the amount of (1,3;1,4)-b-glucan present in sorghum tissues was measured using a Megazyme assay. Very low amounts were present in the grain, ranging from 0.16%-0.27% (w/w), while there was a greater quantity in vegetative tissues at 0.12-1.71% (w/w). The fine structure of (1,3;1,4)-b-glucan, as denoted by the ratio of cellotriosyl and cellotetraosyl residues, was assessed by high performance liquid chromatography (HPLC) and ranged from 2.6-3:1 in the grain, while ratios in vegetative tissues were lower at 2.1-2.6:1. The distribution of (1,3;1,4)-b-glucan was examined using a specific antibody and observed with fluorescence and transmission electron microscopy. Micrographs showed a variable distribution of (1,3;1,4)-b-glucan influenced by temporal and spatial factors. The sorghum orthologs of genes implicated in the synthesis of (1,3;1,4)-b-glucan in other cereals, such as the Cellulose synthase-like (Csl) F and H gene families were defined. Transcript profiling of these genes across sorghum tissues was carried out using real-time quantitative polymerase chain reaction, indicating that, as in other cereals, CslF6 transcripts dominated.

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

“…Eukaryotic CesA genes were first cloned from cotton (Pear et al, 1996) and have been later reported from Arabidopsis (10), maize (12), poplar (18), and 14 in foxtail millet (Richmond and Somerville, 2000; Appenzeller et al, 2004; Djerbi et al, 2005; Muthamilarasan et al, 2015). Cluster analysis of CESA proteins found to be clustered with CSLD and CSLF proteins (Figure 2) consistent with earlier reports (Ermawar et al, 2015a). The clustering is due the presence of common conserved domains among cellulose synthase and cellulose synthase like family of proteins.…”

“…In the present investigation, the large family of sorghum Csls has been classified into 8 different groups (CslA to H) based on the phylogenetic studies (Ermawar et al, 2015a; Figure 2). Particularly, two clusters, CslF and CslH were observed be unique to sorghum with no Arabidopsis homologs, which is in agreement with the previous reports of these clusters as grass specific (Paterson et al, 2009; Ermawar et al, 2015a) while no sorghum Csl genes were clustered in Clusters CslB and CslG (Figure 2). Similar clustering of SbCsl genes has been reported previously in the sorghum draft genome report (Paterson et al, 2009).…”

“…In sorghum, a total of 12 CesA and 36/37 Csl genes have been reported in previous studies (Paterson et al, 2009; Yin et al, 2009). 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).…”

Method for hull‐less barley transformation and manipulation of grain mixed‐linkage beta‐glucan

“…After hydrolysis with lichenase (EC 3.2.1.73; 1,3‐1,4‐beta‐D‐glucan 4‐glucanohydrolase), a portion of the hydrolysate was collected and stored at −20°C for high pH anion exchange chromatography (HPAEC) analysis of the G4G3G (DP3) and G4G4G3G (DP4) oligosaccharides. Hydrolysates were separated on a solid phase extraction (SPE) cartridge packed with graphitized carbon (Varian Bond Elute Carbon 50mg‐1), as outlined in Ermawar et al (). The oligosaccharides were dissolved in 1 mL water and analyzed using HPAEC on a Dionex ICS‐5000 using a DionexCarboPAC PA‐200 column (3 × 250 mm), as outlined by Ermawar et al ().…”

Targeted mutation of barley (1,3;1,4)-β-glucan synthases reveals complex relationships between the storage and cell wall polysaccharide content

“…The DP3:DP4 ratio was determined by High-Performance Anion-Exchange Chromatography (HPAEC) as described in Ermawar et al (2015). Lichenase enzyme (Megazyme Int., Wicklow, Ireland) was used to release oligosaccharides for profiling by HPAEC.…”