Arabinoxylan and (1→3),(1→4)-β-glucan deposition in cell walls during wheat endosperm development

Abstract

Arabinoxylans (AX) and (1-->3),(1-->4)-beta-glucans are major components of wheat endosperm cell walls. Their chemical heterogeneity has been described but little is known about the sequence of their deposition in cell walls during endosperm development. The time course and pattern of deposition of the (1-->3) and (1-->3),(1-->4)-beta-glucans and AX in the endosperm cell walls of wheat (Triticum aestivum L. cv. Recital) during grain development was studied using specific antibodies. At approximately 45 degrees D (degree-days) after anthesis the developing walls contained (1-->3)-beta-glucans but not (1-->3),(1-->4)-beta-glucans. In contrast, (1-->3),(1-->4)-beta-glucans occurred widely in the walls of maternal tissues. At the end of the cellularization stage (72 degrees D), (1-->3)-beta-glucan epitopes disappeared and (1-->3),(1-->4)-beta-glucans were found equally distributed in all thin walls of wheat endosperm. The AX were detected at the beginning of differentiation (245 degrees D) in wheat endosperm, but were missing in previous stages. However, epitopes related to AX were present in nucellar epidermis and cross cells surrounding endosperm at all stages but not detected in the maternal outer tissues. As soon as the differentiation was apparent, the cell walls exhibited a strong heterogeneity in the distribution of polysaccharides within the endosperm.

Pattern of Deposition of Cell Wall Polysaccharides and Transcript Abundance of Related Cell Wall Synthesis Genes during Differentiation in Barley Endosperm

“…Callose has a transient appearance in the cellularizing endosperm except in those regions surrounding plasmodesmata . This pattern of callose deposition in the early endosperm is similar to what has been described for rice and wheat endosperm (Brown et al, 1997;Philippe et al, 2006).…”

“…4B). This specific lack of labeling in the peripheral endosperm cells has also been reported in wheat (Philippe et al, 2006). In wheat, this observed heterogeneity in labeling intensity within the starchy endosperm persists throughout development whereas in barley, by 16 DAP the cell walls of the peripheral endosperm are labeled (Fig.…”

“…During cellularization each polysaccharide is uniformly deposited in the endosperm cell walls except for arabino-(1-4)-b-D-xylan where labeling is restricted to those cell walls immediately adjacent to the grain crease . Similar studies have been performed on developing rice (Oryza sativa; Brown et al, 1997) and wheat (Triticum aestivum) grains (Philippe et al, 2006).…”

“…Therefore, observations on grain development and polysaccharide distribution are only described up to 28 DAP. We and others (Brown et al, 1997;Philippe et al, 2006) have reported the transient nature of (1→3)-b-D-glucan during early endosperm development. Callose is the first polysaccharide to appear in the walls of the cellularizing endosperm at 3 DAP, persisting until around 6 DAP .…”

“…Chemical analysis has shown (1→3, 1→4)-b-D-glucan to be the most abundant polysaccharide in the barley grain (Fincher, 1975). Unlike rice (Brown et al, 1997) but similar to wheat (Philippe et al, 2006) (Fig. 4B).…”