Hormonal regulation of α-amylase inhibitor synthesis in germinating barley

Mundy, John

doi:10.1007/bf02907784

Cited by 45 publications

(27 citation statements)

References 23 publications

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“…These two proteins have been precipitated together here to highlight their different patterns of synthesis. The regulation of synthesis of ASI, both in vivo (21) and in vitro (present study) therefore appears to be the reverse of that for aamylase; synthesis of the inhibitor is enhanced by ABA while it is inhibited by GA3 in comparison to untreated aleurones.…”

Section: Resultsmentioning

confidence: 53%

“…5, lanes 4-6; Table II) is essentially the same as that previously described in vivo (21). These two proteins have been precipitated together here to highlight their different patterns of synthesis.…”

Section: Resultsmentioning

confidence: 85%

“…Another protein whose synthesis in vivo is specifically regulated in cultured aleurone layers by these hormones has been identified as a seed protein ASI2 which inhibits both barley a-amylase and the bacterial protease subtilisin (20). Interestingly, ASI synthesis in vivo was stimulated in aleurone layers by ABA but reduced by GA, a control antagonistic to that for a-amylase (21). These results have led to speculation on the role of ASI and other seed proteins in aleurone layers, and generally on the effect of ABA on protein synthesis in the mRNAs FROM BARLEY ALEURONE AND STARCHY ENDOSPERM aleurone tissue system ( 12,21).…”

mentioning

confidence: 99%

“…Interestingly, ASI synthesis in vivo was stimulated in aleurone layers by ABA but reduced by GA, a control antagonistic to that for a-amylase (21). These results have led to speculation on the role of ASI and other seed proteins in aleurone layers, and generally on the effect of ABA on protein synthesis in the mRNAs FROM BARLEY ALEURONE AND STARCHY ENDOSPERM aleurone tissue system ( 12,21).…”

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confidence: 99%

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Differential Synthesis in Vitro of Barley Aleurone and Starchy Endosperm Proteins

Mundy¹,

Hejgaard²,

Hansen³

et al. 1986

Plant Physiol.

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To widen the selection of proteins for gene expression studies in barley seeds, experiments were performed to identify proteins whose synthesis is differentially regulated in developing and germinating seed tissues. The in vitro synthesis of nine distinct barley proteins was compared using mRNAs from isolated endosperm and aleurone tissues (developing and mature grain) and from cultured (germinating) aleurone layers treated with abscisic acid (ABA) and GA3. B and C hordein polypeptides and the salt-soluble proteins O-amylase, protein Z, protein C, the chymotrypsin inhibitors (CI-I and 2), the a-amylase/subtilisin inhibitor (ASI) and the inhibitor of animal cell-free protein synthesis systems (PSI) were synthesized with mRNA from developing starchy endosperm tissue. Of these proteins, f6-amylase, protein Z, and CI-1 and 2 were also synthesized with mRNA from developing aleurone cells, but ASI, PSI, and protein C were not. CI-I and also a probable amylase/protease inhibitor (PAPI) were synthesized at high levels with mRNAs from late developing and mature aleurone. These results show that mRNAs encoding PAPI and CI-I survive seed dessication and are long-lived in aleurone cells. Thus, expression of genes encoding ASI, PSI, protein C, and PAPI is tissue and stage-specific during seed development. Only ASI, CI-I, and PAPI were synthesized in significant amounts with mRNA from cultured aleurone layers. The levels of synthesis of PAPI and CI-1 were independent of hormone treatment. In contrast, synthesis of a-amylase (included as control) and of ASI showed antagonistic hormonal control: while GA promotes and ABA reduces accumulation of mRNA for a-amylase, these hormones have the opposite effect on ASI mRNA levels.One approach to understanding the molecular mechanisms controlling seed maturation and germination is to study organspecific, developmentally characteristic, and hormonally regulated seed proteins and their mRNAs. Earlier studies have identified such polypeptides in Gossypium (7) and Brassica (6) and have formed the basis of later work at the molecular level on these crops. We report here the results of similar experiments with barley seeds, a cereal of importance as livestock feed and as malt in the brewing industry.The barley seed or caryopsis is comprised of several tissues derived from the fertilized ovule (4). The seed proteins of the grain, synthesized during seed development in the endosperm and/or aleurone layer, include the hordeins (30-50% of total N, ' Present address:

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Section: Resultsmentioning

confidence: 53%

Section: Resultsmentioning

confidence: 85%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Differential Synthesis in Vitro of Barley Aleurone and Starchy Endosperm Proteins

Mundy¹,

Hejgaard²,

Hansen³

et al. 1986

Plant Physiol.

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“…102, 1993 nous GA and ABA concentrations strongly controls a-amylase gene expression in intact germinating seedlings, although a cultivar's sensitivity to each hormone would shift the effective (perceived) balance. ABA also induces the accumulation of the a-amylase inhibitor bifunctional a-amylasel subtilisin inhibitor (Mundy, 1984). In addition to hormonal and other physiological controls, cultivar-specific differences in expression could be caused by gene sequence variations.…”

Section: Molecular Studies Of A-amylase Gene Expression In Barleymentioning

confidence: 99%

Aleurones from a Barley with Low [alpha]-Amylase Activity Become Highly Responsive to Gibberellin When Detached from the Starchy Endosperm

Skadsen

1993

Plant Physiol.

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The physiological and molecular bases for contrasting a-amylase phenotypes were examined in germinating seeds of two barley (Hordeum vurgare 1.) cultivars, Morex and Steptoe. Morex is a high-quality malting barley that develops high a-amylase activity soon after germination. Steptoe is a feed barley that develops only low a-amylase activity levels during this period. l h e expression of all high-and low-isoelectric point (pl) a-amylase isozymes is reduced in Steptoe. The amount of a-amylase mRNA per gram of seedling tissue is correspondingly lower in Steptoe. Southern blot analysis revealed that the cultivars have the same copy number and organization for most high-and low-pl genes. Steptoe seedlings or embryoless half-seeds produce little a-amylase in response to exogenous applications of gibberellic acid (CA,) compared with Morex. However, when isolated aleurones of both cultivars are treated with GA3, they produce similar amounts of high-and lowpl a-amylase RNAs. This suggests that a factor in the starchy endosperm is responsible for lowered a-amylase response in Steptoe. l h e factor is probably not abscisic acid (ABA), since the two cultivars have similar concentrations of ABA during germination.

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The Protein Reserves of the Barley Grain and Their Degradation During Malting and Brewing

Wallace

Lance

1988

Journal of the Institute of Brewing

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The hordeins of barley are the main components of the grain protein, comprising B (sulphur rich), C (sulphur poor) and D (high relative molecular mass) species. A gel fraction can be isolated that consists of the D and part of the B hordein. Other important components of the reserve protein are B-amylase, protein Z and enzyme inhibitors as well as endosperm cell wall protein and protein associated with the starch granules.Degradation of protein is mediated by peptidase enzymes, most important of which are the endopeptidases and the exopeptidases; the latter having specificity for the carboxy-or amino-terminal region of a polypeptide chain. A very high activity of carboxypeptidase develops In the germinating barley grain. Five carboxypeptidases have been identified in malt and three fully characterized. Several endopeptidases have been identified, which have optimum activity close to pH 5.0 (that of the starchy endosperm) and studies with active site Inhibitors suggest that sulphydryl dependent species are the most important However, only limited use has been made of hordein as a substrate in the measurement of peptidase activity in malt Lack of a complete understanding on the peptidases and their regulation in the germinating barley is a major limiting factor in the knowledge on the mobilization of the protein reserves during malting and mashing. Both de novo synthesis and activation of the peptidases have been demonstrated and the hormones gibberellic acid and abscisic acid appear to have a regulatory role. A controlled modification of the protein reserve is required so that there is an appropriate supply of amino acids for the brewers yeast but retention of proteins important in the desirable foaming component of beer. It is also important that proteins which can interfere in the final stages of brewing, e.g. those with chill haze forming potential, are broken down. An early hydrolysis is required of cell wall proteins and those proteins intimately associated with the starch granules.

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Hormonal regulation of α-amylase inhibitor synthesis in germinating barley

Cited by 45 publications

References 23 publications

Differential Synthesis in Vitro of Barley Aleurone and Starchy Endosperm Proteins

Differential Synthesis in Vitro of Barley Aleurone and Starchy Endosperm Proteins

Aleurones from a Barley with Low [alpha]-Amylase Activity Become Highly Responsive to Gibberellin When Detached from the Starchy Endosperm

The Protein Reserves of the Barley Grain and Their Degradation During Malting and Brewing

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