Barley grain (1,3;1,4)-β-glucan content: effects of transcript and sequence variation in genes encoding the corresponding synthase and endohydrolase enzymes

Abstract

The composition of plant cell walls is important in determining cereal end uses. Unlike other widely consumed cereal grains barley is comparatively rich in (1,3;1,4)-β-glucan, a source of dietary fibre. Previous work showed Cellulose synthase-like genes synthesise (1,3;1,4)-β-glucan in several tissues. HvCslF6 encodes a grain (1,3;1,4)-β-glucan synthase, whereas the function of HvCslF9 is unknown. Here, the relationship between mRNA levels of HvCslF6, HvCslF9, HvGlbI (1,3;1,4)-β-glucan endohydrolase, and (1,3;1,4)-β-glucan content was studied in developing grains of four barley cultivars. HvCslF6 was differentially expressed during mid (8–15 DPA) and late (38 DPA) grain development stages while HvCslF9 transcript was only clearly detected at 8–10 DPA. A peak of HvGlbI expression was detected at 15 DPA. Differences in transcript abundance across the three genes could partially explain variation in grain (1,3;1,4)-β-glucan content in these genotypes. Remarkably narrow sequence variation was found within the HvCslF6 promoter and coding sequence and does not explain variation in (1,3;1,4)-β-glucan content. Our data emphasise the genotype-dependent accumulation of (1,3;1,4)-β-glucan during barley grain development and a role for the balance between hydrolysis and synthesis in determining (1,3;1,4)-β-glucan content, and suggests that other regulatory sequences or proteins are likely to be involved in this trait in developing grain.

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

“…To assess the distribution of (1,3;1,4)‐β‐glucan in WT grain compared with lines carrying induced mutations, we used immunolabelling with the BG1 antibody (Burton et al ., 2011). Developmental stages for analysis were selected based on the transcript abundance of the target genes; for HvCslF6 , we sampled mature grain; and for HvCslF9 , we sampled grain at 15 DPA, as this follows the peak of expression of this gene (Burton et al ., 2008; Garcia‐Gimenez et al ., 2019).…”

“…HvCslF9 expression in developing grain is generally low but shows a prominent peak at about 8 DPA (cv. Sloop; Burton et al ., 2008), although this varies depending on the cultivar (Garcia‐Gimenez et al, 2019). In cv.…”

Genome-Wide Association Mapping of Mixed Linkage (1,3;1,4)-β-Glucan and Starch Contents in Rice Whole Grain

“…The MLG content was reported to account for 20% of the total dietary fiber content in wheat (Prasadi and Joye, 2020). Wirkijowska et al (2012) reported that the content of (1-3) (1-4)-β-D-glucans in barley kernel ranged between 4.04 and 5.71% of dry matter, and Garcia-Gimenez et al (2019) expressed that barley has a considerably higher MLG content (4-10%) compared with wheat (1%) or rice (<0.06%), although (Fincher, 2009a) reported that (1-3) (1-4)-β-D-glucans constitute up to 70% of starchy endosperm in barley. In all these reports, the amount of MLG was measured in a few samples/accessions.…”

Whole-Grain Intake in the Mediterranean Diet and a Low Protein to Carbohydrates Ratio Can Help to Reduce Mortality from Cardiovascular Disease, Slow Down the Progression of Aging, and to Improve Lifespan: A Review

“…Β-glucan constitutes approximatively 75% of dry weight of endosperm cell walls, and arabinoxylan constitutes 25% [ 75 ]. The percentages of beta-glucan content in the barley grain vary according to the different polymorphisms of the genes that encode the corresponding synthase and endohydrolase enzymes [ 76 ]. Barley β-glucans also have cholesterol-lowering properties [ 77 , 78 ], however, lower than oats [ 79 ].…”