Temperature effects on starch granules in developing barley grains

MacLeod, L.; Duffus, C. M.

doi:10.1016/s0733-5210(88)80046-8

Cited by 32 publications

(22 citation statements)

References 17 publications

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“…6a). These expression patterns correspond closely to the timing of starch synthesis in developing barley grains, although the latter is dependent to some extent on growth temperatures (MacLeod and Duffus, 1988). Given the relatively low levels of limit dextrinase mRNA in developing endosperm (Fig.…”

Section: Discussionsupporting

confidence: 54%

A Single Limit Dextrinase Gene Is Expressed Both in the Developing Endosperm and in Germinated Grains of Barley1

1999

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The single gene encoding limit dextrinase (pullulan 6-glucanohydrolase; EC 3.2.1.41) in barley (Hordeum vulgare) has 26 introns that range in size from 93 to 822 base pairs. The mature polypeptide encoded by the gene has 884 amino acid residues and a calculated molecular mass of 97,417 D. Limit dextrinase mRNA is abundant in gibberellic acid-treated aleurone layers and in germinated grain. Gibberellic acid response elements were found in the promoter region of the gene. These observations suggest that the enzyme participates in starch hydrolysis during endosperm mobilization in germinated grain. The mRNA encoding the enzyme is present at lower levels in the developing endosperm of immature grain, a location consistent with a role for limit dextrinase in starch synthesis. Enzyme activity was also detected in developing grain. The limit dextrinase has a presequence typical of transit peptides that target nascent polypeptides to amyloplasts, but this would not be expected to direct secretion of the mature enzyme from aleurone cells in germinated grain. It remains to be discovered how the enzyme is released from the aleurone and whether another enzyme, possibly of the isoamylase group, might be equally important for starch hydrolysis in germinated grain.Starch is the major carbohydrate reserve in cereal grains, where it is located in the nonliving cells of the starchy endosperm and constitutes up to 60% of total grain dry weight (Aman et al., 1985). Starch consists of the essentially linear (134)-␣-glucan amylose, together with the branched (134,136)-␣-glucan amylopectin. The two polysaccharides are organized in semicrystalline starch granules, which in barley (Hordeum vulgare) grain contain 70% to 75% amylopectin and 25% to 30% amylose (for review, see MacGregor and Fincher, 1993).Following germination, the glucosyl residues of amylose and amylopectin are released to support seedling growth by the concerted action of ␣-amylases, ␤-amylases, debranching enzymes, and ␣-glucosidases. The debranching enzymes catalyze the hydrolysis of (136)-␣-glucosidic linkages in amylopectin or in (134,136)-␣-oligoglucosides released by ␣-amylases. Because the (136)-␣-glucosyl linkages in these oligoglucosides, which are also referred to as limit dextrins, are not hydrolyzed by ␣-or ␤-amylases, and because the action of ␣-glucosidase on branched oligoglucosides is relatively slow, debranching enzymes are considered to play a central role in the complete depolymerization of starch to Glc. The debranched oligosaccharides are susceptible to further hydrolysis by amylases and ␣-glucosidases (Lee et al., 1971).Starch-debranching enzymes have been divided into two groups based on differences in their substate specificities and action patterns (Lee et al., 1971). The first group includes the pullulanases (pullulan 6-glucanohydrolase; EC 3.2.1.41), endohydrolases capable of hydrolyzing (136)-␣-linkages in pullulan, a polysaccharide consisting of maltotriosyl residues linked by (136)-␣-linkages. The second group includes isoamylases (glycogen...

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Section: Discussionsupporting

confidence: 54%

A Single Limit Dextrinase Gene Is Expressed Both in the Developing Endosperm and in Germinated Grains of Barley1

1999

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“…Sucrose synthase activity and starch deposition decrease in the endosperm when day/night temperatures are raised from 20/15°C to 30/25°C, even though the sucrose concentration increases (MacLeod and Duffus 1988b). Temperatures in the range of 15-30°C do not affect endosperm cell number (MacLeod and Duffus 1988a). The duration of grain filling is negatively correlated with mean air temperature during this stage, while rate of grain filling is positively correlated .…”

Section: Grain Fillingmentioning

confidence: 90%

“…Temperatures above 15°C lower starch and protein content and individual grain weight, and increase lipid content; the size of A-and B-type starch granules and the number of B-type starch granules is decreased (MacLeod and Duffus 1988a;Tester et al 1991). Temperatures above 35°C are associated with increased grain protein (Correll et al 1994).…”

Section: Grain Fillingmentioning

confidence: 99%

Barley: Physiology of Yield

Smith¹,

Dijak²,

Bulman³

et al. 1999

Crop Yield

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Physiology describes the operation of a plant at the biochemical, cell, tissue, organ and whole plant levels, recognizing that all of these are under the control of the plant genome. In the case of crop plants we are interested in how the combined operation of all plant's functions leads to the production of the harvestable component which, in cereal crops, is generally grain. Broadly speaking, the most important of the physiological activities in a crop plant with regard to yield are dry matter production, nutrient uptake, plant component partitioning and the processes of development (especially grain filling and the other aspects of yield component development). The developmental processes occur sequentially in time and involve progressive shifts in physiology. As barley (Hordeum vulgare L.) is a feed grain and a major source of malting grain for beer and spirits, aspects of physiology that affect the amount of grain produced and its quality (the amount of energy and protein) are of special interest.

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“…11 By contrast, MacLeod and Duffus 10 found that elevated temperatures reduced numbers rather than sizes of both A-type and B-type granules. The relationship between growth temperature and granule number per unit weight of starch may therefore be fairly complex.…”

Section: Domonmentioning

confidence: 95%

Combining high‐amylose and waxy starch mutations in barley

Swanston¹,

Ellis²,

Morrison³

et al. 2001

J Sci Food Agric

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Inbred lines, from a cross between barleys carrying the waxy and high-amylose genes respectively, were characterised by the presence of both, either or neither of the genes and grown under ®eld conditions. Starch granule proteins were separated by SDS-PAGE and lines carrying the waxy gene, with or without the high-amylose gene, had greatly reduced intensities of the 60 kDa band associated with granule-bound starch synthase. One representative sample of each starch type was also grown under two controlled environment (CE) regimes. Starch properties were assessed on ®eld-and CE-grown samples of these genotypes and large differences were observed among starch types. Growth conditions generally had comparatively little effect on the starch properties measured. The waxy and high-amylose genes appeared to have additive effects, both in reducing modal granule size and in increasing gelatinisation temperature signi®cantly above that observed when only one of the genes was present. The genotype with both mutations produced a starch with phosphorus content and blue value, after removal of lipid, slightly higher than those of the waxy type and with an RVA pro®le similar to that of the wild type, but with lower peak and ®nal viscosities.

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Temperature effects on starch granules in developing barley grains

Cited by 32 publications

References 17 publications

A Single Limit Dextrinase Gene Is Expressed Both in the Developing Endosperm and in Germinated Grains of Barley1

A Single Limit Dextrinase Gene Is Expressed Both in the Developing Endosperm and in Germinated Grains of Barley1

Barley: Physiology of Yield

Combining high‐amylose and waxy starch mutations in barley

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