Observations on the Aleurone Layer. II. Fluorescence Microscopy of the Aleurone-Sub-Aleurone Junction With Emphasis on Possible β-1,3-Glucan Deposits in Barley

Abstract

The structural organization of the cell walls at the aleurone-sub-aleurone junction has been examined by fluorescence microscopy in ungerminated seeds of two varieties of Hordeum vulgare L. (cultivars Himalaya and Vanier). The sub-aleurone cell walls that are immediately adjacent to the aleurone layer are considerably thicker than the remainder of endosperm walls and contain extensive deposits of aniline blue-positive material. The latter was not significantly affected by periodate oxidation and was removed from tissue sections only by β-1,3-glucanases or hot dimethyl sulphoxide. These deposits may represent the primary substrate for endo-β-1,3-glucanases secreted by the aleurone layer during germination.

Purification and amino acid sequence determination of an endo-1,3-β-glucanase from barley

“…It thus belongs to the enzyme category EC 3.2.1.39 as opposed to EC 3.2.1.6. A potential substrate in barley and wheat for this enzyme is the aniline blue stainable deposits localized in the aleurone-subaleurone junction region (1,13). These deposits in barley have now been shown to be degradable by endo-1,3-13-giucanase purified in this study (MACGREGOR, BALLANCE and DUSHNICKY, manuscript in preparation) adding further evidence of the 1,3-13-glucan nature of these deposits.…”

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

“…2A). Fulcher et al (1977) suggests that these deposits may be the primary substrate for high levels of b-(1,3)-glucanase activity present at the onset of germination. Both Fulcher et al (1977) and Bacic and Stone (1981a) recognized that variation in the pattern and size of callose deposits between barley varieties does not support a specific physiological function, although Fincher (1989) suggested that the variable patterns of callose distribution might have reflected a variable number of transient water stress events that caused plasmolysis and callose deposition during grain development.…”

“…Both Fulcher et al (1977) and Bacic and Stone (1981a) recognized that variation in the pattern and size of callose deposits between barley varieties does not support a specific physiological function, although Fincher (1989) suggested that the variable patterns of callose distribution might have reflected a variable number of transient water stress events that caused plasmolysis and callose deposition during grain development. The deposits may either influence the movement of substances during germination or they could simply be a remnant of developing walls (Fulcher et al, 1977). However, another possible explanation is that callose is being synthesized as a wound response.…”

“…Fulcher et al (1977) described different labeling patterns in two barley varieties: One, cv Vanier, shows a continuous layer of the aniline blue fluorochrome whereas the other, cv Himalaya, has discrete patches of fluorescence along the thick walls directly adjacent to the aleurone. Similarly, Bacic and Stone (1981a) observed a continuous layer of aniline blue fluorochrome staining at the subaleurone/aleurone interface in wheat (cv Insignia) while describing droplets of fluorescent material at the same location for barley (cv Himalaya).…”

“…Early studies on wheat and barley grains report callose in mature endosperm cell walls as evidenced by deposits of the aniline blue fluorochrome at the aleurone/starchy endosperm interface (Fulcher et al, 1977;Bacic and Stone, 1981a). Fulcher et al (1977) described different labeling patterns in two barley varieties: One, cv Vanier, shows a continuous layer of the aniline blue fluorochrome whereas the other, cv Himalaya, has discrete patches of fluorescence along the thick walls directly adjacent to the aleurone.…”