Identification of genes involved in the formation of soluble dietary fiber in winter rye grain and their expression in cultivars with different viscosities of wholemeal water extract

The grain of rye(Secale cereale L.) used for baking contains a large amount of non-starch polysaccharides,making it an excellent component of functional foods. But rye grain intended for alcohol production and forage use should have a reduced content of these polysaccharides. A comprehensive parameter that can predict the best field of application for winter rye grain is the viscosity of its wholemeal water extract.However, our understanding of the genetic background underlying this key trait and associated features of rye grain is poor. By analyzing six Russian winter rye cultivars, we identified the most contrasting forms and characterized the peculiarities of their water-soluble carbohydrates capable of influencing the viscosity of water extracts. Then, using phylogenetic and transcriptomic analyses, we identified in the rye genome many genes encoding putative glycosyltransferases and glycosylhydrolases responsible for the synthesis and degradation of arabinoxylans, mixed-linkage glucans, cellulose, and some other polysaccharides. We determined the dynamics of m RNA abundance for these genes at three stages of kernel development. Comparisons of gene expression levels in two contrasting cultivars revealed specific members of multigene families that may serve as promising targets for manipulating non-starch polysaccharide content in rye grain. High-viscosity cultivars were characterized by up-regulation of many glycosyltransferases involved in the biosynthesis of arabinoxylans and other cell-wall polysaccharides,whereas low-viscosity cultivars showed up-regulation of several genes encoding polysaccharidedegrading enzymes.

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

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 fl uorescence and transmission electron microscopy. Micrographs showed a variable distribution of（1,3;1,4）-b-glucan in fl uenced 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 de fined.Transcript pro filing of these genes across sorghum tissues was carried out using real-time quantitative polymerase chain reaction, indicating that, as in other cereals, Csl F6 transcripts dominated.