The ultrastructure of germinating barley seeds. II. Breakdown of starch granules and cell walls of the endosperm in three barley varieties

Gram, Niels H.

doi:10.1007/bf02904380

Cited by 20 publications

(8 citation statements)

References 15 publications

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“…It seems highly likely that the diffusion of α-amylase from the aleurone into the endosperm is prevented or strongly retarded by intact cell walls. Previous authors have shown that the temporal and spatial patterns of cell wall and starch degradation are similar and proposed that cell wall degradation may be important for starch degradation 39 , but our data constitute the first experimental evidence for a causal relationship between these processes.…”

Section: Discussionsupporting

confidence: 62%

Cell wall degradation is required for normal starch mobilisation in barley endosperm

Andriotis

Rejzek

Barclay

et al. 2016

Sci Rep

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Starch degradation in barley endosperm provides carbon for early seedling growth, but the control of this process is poorly understood. We investigated whether endosperm cell wall degradation is an important determinant of the rate of starch degradation. We identified iminosugar inhibitors of enzymes that degrade the cell wall component arabinoxylan. The iminosugar 1,4-dideoxy-1, 4-imino-l-arabinitol (LAB) inhibits arabinoxylan arabinofuranohydrolase (AXAH) but does not inhibit the main starch-degrading enzymes α- and β-amylase and limit dextrinase. AXAH activity in the endosperm appears soon after the onset of germination and resides in dimers putatively containing two isoforms, AXAH1 and AXAH2. Upon grain imbibition, mobilisation of arabinoxylan and starch spreads across the endosperm from the aleurone towards the crease. The front of arabinoxylan degradation precedes that of starch degradation. Incubation of grains with LAB decreases the rate of loss of both arabinoxylan and starch, and retards the spread of both degradation processes across the endosperm. We propose that starch degradation in the endosperm is dependent on cell wall degradation, which permeabilises the walls and thus permits rapid diffusion of amylolytic enzymes. AXAH may be of particular importance in this respect. These results provide new insights into the mobilization of endosperm reserves to support early seedling growth.

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Section: Discussionsupporting

confidence: 62%

Cell wall degradation is required for normal starch mobilisation in barley endosperm

Andriotis

Rejzek

Barclay

et al. 2016

Sci Rep

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“…The non-release of 'cytase' and 'diastase' from scutella from which the epithelium been removed as noted by Brown and Morris 13 , who also noted that the 'face' of the scutellum, (sliced from the embryo), released enzymes into a nutrient gel and that starch and cell walls were degraded under the full area of the scutellum in vitro and that endosperm degradation began under all parts of the scutellum in the germinating grain are all facts that support the importance of the scutellar epithelium and minimize the importance of residual aleurone tissue. The cytological changes which occur in the epithelium are typical of secretory cells 13,56,57 . Plugs of scutellar tissue, totally devoid of peripheral aleurone tissue, release ␣-amylase 50,58 .…”

Section: LI 6spiw Sj Xli )Qfv]s Erh Xli %Piyvsri 0e]ivmentioning

confidence: 99%

Malt Modification - A Century Of Evolving Views

Briggs

2002

Journal of the Institute of Brewing

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This lecture is the 22nd to commemorate Horace Taberrer Brown, a truly remarkable polymath who made important contributions to brewing practice and science and to 'pure' science. The ideas that Brown and his collaborators developed in the 1890s regarding the origins of the enzymes which catalyse the modification of the endosperm of germinating barley and how modification progresses through the grain are summarized, then the stages by which our understanding has been enhanced are noted. The discovery of gibberellins, their use in malting, the role they play in germinating grain, and how this knowledge has suggested ways to make malts with reduced malting losses are outlined. The discrepant reported patterns of modification and true 'average' patterns are described. It is pointed out that abrasion does not work by inducing two-way modification, as originally proposed. This successful process probably depends on improved access of oxygen to the living grain tissues. Microbes on the grain compete with the embryo and aleurone layer for oxygen, to the detriment of germination and modification. Commercially acceptable ways in which the activities of microbes might be reduced (and malting enhanced) are discussed, including the use of plug-rinses at the end of steeps to reduce the microbial population and the quantity of the microbial nutrients which support growth and respiration and are dissolved in the water around the grains. A newly-proposed method for the bulk-selection of malting quality lines from mixed populations of barley is mentioned. Finally, the dangers to the malting and brewing industries in the U.K. of the continuing reduction in scientific research is indicated.

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“…They found that the endosperm of Julia appeared to be more rigid and compact than the equivalent endosperm of Proctor, but they did not report any differences in cell wall thickness. Similary GRAM (14) could detect no differences between cell walls of varieties of varying malting quality (Minerva, Nordal and Klages) by freezefracture techniques. The reason that differences in cell wall thickness have not been observed might be that i) the differences have been too small, ii) different parts of the endosperm have been examined, iii) insufficient (or non-representative) cell wall sections have been measured, iv) there was, indeed, no difference in the cell wall thickness.…”

Section: Discussionmentioning

confidence: 88%

“…The low 13-glucan, thin-walled mutant malted much more quickly than the high 13-glucan parent variety, supporting the views of MACLEOD (20), that the biggest obstacle to the conversion of barley to satisfactory malt is the network of endosperm cell walls. This view is based on the suggestion that the 13-glucan-rich cell walls must be broken down before any hydrolysis of starch and protein takes place and has been recently demonstrated by GRAM (14). Furthermore, a comparison of the malting ofM-737 and M-1460 shows the importance of high 13-glucanase activity for the rate of modification as pointed out by WAINWm6HT (32).…”

Section: Discussionmentioning

confidence: 91%

Selection and characterization of low β-glucan mutants from barley

Aastrup

1983

Carlsberg Res. Commun.

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Four barley lines have been selected from 40,000 M 2 plants derived from sodium azide-treated seeds of the high [3-glucan cultivar Minerva, on the basis of low viscosity of acid extracts of flour. Two lines show a minor decrease in total ~-glucan content, and two lines are low in total [3-glucan, exhibit rapid endosperm modification and display a mealy endosperm. The thickness of the endosperm cell walls in the low [~-glucan mutants is 3.0-3.5/am compared with 6.5 lam for the parent variety Minerva. One of the low B-glucan mutants, has increased 13-glucanase activity which might partly explain the increased rate of its modification during malting. The other mutant, M-737, has approximately the same amount of [~-glucanase as Minerva and appears to be a genuine low [3-glucan mutant. Malting studies confirmed the important role of endosperm cell walls as a barrier for enzyme dissemination.

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The ultrastructure of germinating barley seeds. II. Breakdown of starch granules and cell walls of the endosperm in three barley varieties

Cited by 20 publications

References 15 publications

Cell wall degradation is required for normal starch mobilisation in barley endosperm

Cell wall degradation is required for normal starch mobilisation in barley endosperm

Malt Modification - A Century Of Evolving Views

Selection and characterization of low β-glucan mutants from barley

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