RNA Interference Suppression of Genes in Glycosyl Transferase Families 43 and 47 in Wheat Starchy Endosperm Causes Large Decreases in Arabinoxylan Content

Abstract

The cell walls of wheat (Triticum aestivum) starchy endosperm are dominated by arabinoxylan (AX), accounting for 65% to 70% of the polysaccharide content. Genes within two glycosyl transferase (GT) families, GT43 (IRREGULAR XYLEM9 [IRX9] and IRX14) and GT47 (IRX10), have previously been shown to be involved in the synthesis of the xylan backbone in Arabidopsis, and close homologs of these have been implicated in the synthesis of xylan in other species. Here, homologs of IRX10 TaGT47_2 and IRX9 TaGT43_2, which are highly expressed in wheat starchy endosperm cells, were suppressed by RNA interference (RNAi) constructs driven by a starchy endosperm-specific promoter. The total amount of AX was decreased by 40% to 50% and the degree of arabinosylation was increased by 25% to 30% in transgenic lines carrying either of the transgenes. The cell walls of starchy endosperm in sections of grain from TaGT43_2 and TaGT47_2 RNAi transgenics showed decreased immunolabeling for xylan and arabinoxylan epitopes and approximately 50% decreased cell wall thickness compared with controls. The proportion of AX that was water soluble was not significantly affected, but average AX polymer chain length was decreased in both TaGT43_2 and TaGT47_2 RNAi transgenics. However, the long AX chains seen in controls were absent in TaGT43_2 RNAi transgenics but still present in TaGT47_2 RNAi transgenics. The results support an emerging picture of IRX9-like and IRX10-like proteins acting as key components in the xylan synthesis machinery in both dicots and grasses. Since AX is the main component of dietary fiber in wheat foods, the TaGT43_2 and TaGT47_2 genes are of major importance to human nutrition.

Breeding maize for silage and biofuel production, an illustration of a step forward with the genome sequence

“…Candidate genes for xylan synthase have been identified as members of the GT43 (IRX9/14-like) and GT47 (IRX10-like) families, although the precise contribution of both protein families remains unclear [90,91]. Rice OsGT47A (also named OsIRX10) mutants had a reduced level of xylans and showed an increase in saccharification efficiency [92] .…”

Dietary Fibre: Wheat Genes for Enhanced Human Health

“…Suppression of either gene had similar effects with AX content decreased to about 50 % of controls as determined by monosaccharide composition of non-starch polysaccharide ( Fig. 46.3a ; Lovegrove et al 2013 ). In contrast to suppression of TaGT61_1, the amount of arabinose substitution was increased (Fig.…”

Current potential and limitations of immunolabeling in cereal grain research

“…Maize (Galuszka et al, 2005) Aleurone Arabinoxylan Wheat (Beaugrand et al, 2005;Beaugrand, Reis, et al, 2004;Guillon et al, 2004;Lovegrove et al, 2013;Philippe et al, 2006;Philippe et al, 2007;Robert et al, 2011;Suliman et al, 2013); oat, rye ; barley Xylan Wheat (Lovegrove et al, 2013) Xyloglucan Barley (13),(14)--D-glucan Wheat Philippe et al, 2006;Robert et al, 2011;; barley Callose Wheat (Philippe et al, 2006); barley (Wilson et al, 2012) Mannan Barley Ferulic acid Wheat (Philippe et al, 2007;Robert et al, 2011) p-Coumaric acid Wheat Tranquet et al, 2009) Xylanase Wheat (Beaugrand, Cronier, et al, 2004;Beaugrand et al, 2005;Beaugrand, Reis, et al, 2004) Glycosyltransferase Wheat (Suliman et al, 2013) Oxalate oxidase Wheat ( Wheat (Van Herpen et al, 2008;Wiley et al, 2007) Oleosin / Caleosin Rice (Chen et al, 2012); oat (Heneen et al, 2008) Puroindolines Wheat (Capparelli et al, 2005) Transfer cells Arabinoxylan Wheat Lovegrove et al, 2013;Robert et al, 2011); oat, rye, barley …”

“…Xylan Wheat (Lovegrove et al, 2013) (13),(14)--D-glucan Wheat Ferulic acid Wheat Cell wall invertase Maize (Kang et al, 2009) …”

“…Wheat Guillon et al, 2004;Lovegrove et al, 2013;Philippe et al, 2006;Philippe et al, 2007); oat, rye ; barley Wilson et al, 2006;) Xylan Wheat (Lovegrove et al, 2013) Xyloglucan Wheat (Pellny et al, 2012); barley (Dwivany et al, 2009; (13),(14)--D-glucan Wheat Philippe et al, 2006); barley (Wilson et al, 2006;; maize (Carpita and McCann, 2010) Callose Wheat (Pellny et al, 2012;Philippe et al, 2006); barley (Wilson et al, 2006; Mannan Wheat (Pellny et al, 2012) (Furukawa et al, 2003;Nagamine et al, 2011;Ohdaira et al, 2011;Saito et al, 2009;Saito et al, 2008;Takahashi et al, 2005;Tian et al, 2013;Washida et al, 2009;Yasuda et al, 2009); maize (Arcalis et al, 2010;Chikwamba et al, 2003;Holding et al, 2007) Globulin Wheat (Arcalis et al, 2004); rice Tian et al, 2013); maize (Arcalis et al, 2010) Glutelin Wheat (Arcalis et al, 2004;Wang et al, 2013) Oat (Mohammadi et al, 2007) Binding protein (BiP) Rice Embryo and scutellum Dehydrin Quinoa (Carjuzaa et al, 2008) Oleosin / Caleosin Rice (Chen et al, 2012); oat (Heneen et al, 2008); barley (Liu et al, 2005) Prolamin Rice (Ohdaira et al, 2011) Cytokinin dehydrogenase Maize …”