Production of gibberellin-like substance in the embryo of barley during germination

Yomo, Harugoro; Iinuma, Hironobu

doi:10.1007/bf00390130

Cited by 50 publications

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“…The embryo secretes gibberellin (13,34,44), and it has been shown that exogeneously applied gibberellic acid causes considerable ultrastructural changes in aleurone cells (32,33). This discovery led to a large number of investigations concerning the mode of action of gibberellic acid on isolated aleurone layers, and the capability of aleurone cells to produce enzymes necessary for the degradation of the endosperm in the seed is now well established (5,15,17,19,20,21,23,39,40).…”

Section: Introductionmentioning

confidence: 99%

The ultrastructure of germinating barley seeds. I. Changes in the scutellum and the aleurone layer in Nordal barley

Gram

1982

Carlsberg Res. Commun.

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The ultr~tstructure of the scutellum and the aleurone layer has been examined in seeds of Nordal barley following malting for 0, 30, 72, 120 and 162 hours at 15 ~ Thick sections from the seeds were stained with Calcofluor White M2R New and examined in the light microscope to determine the extent of cell wall degradation in the endosperm.The changes in the scutellar parenchyma cells include degradation of the protein bodies and the appearance of vacuoles and prominent amyloplasts. The analysis of a serially sectioned epithelial cell from the scutellum 72 hours after the start of malting revealed a large number of Golgi apparatuses, preferentially located near the cell wall. It is suggew that the presence and location of the Golgi apparatuses are related to enzyme secretion. Following malting for 72 hours or more, the epithelial cells contain lomasomes and membrane aggregates, termed membrane bodies. The analysis indicated that lomasomes originate from the membrane bodies and are involved in the growth of the cell walls of the epithelium. Organelles indicating cellular activity, i.e., rough endoplasmic reticulum, mitochondria and Golgi apparatuses, first appear in the epithelial cells of the scutellum, and later in the cells of the aleurone layer. Furthermore, the degradation of the endosperm starts in the vicinity of the scutellum as judged by the ca|cofiuor staining. Therefore, it is concluded that the scuteltar epithelium provides the enzymes during the initial degradation of the endosperm. In seeds malted for 162 hours, aleurone ceils with a cytoplasmic organisation indicative of active metabolism are located in the embryo part of the seed, whereas aleurone ceils adjacent to unmodified endosperm in the distal end of the same seed show little or no structural sign of activity.

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Section: Introductionmentioning

confidence: 99%

The ultrastructure of germinating barley seeds. I. Changes in the scutellum and the aleurone layer in Nordal barley

Gram

1982

Carlsberg Res. Commun.

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“…The hypothesis rests on the apparent production of GAlike substances by isolated embryos as shown by bioassay in several experiments (5,12,(18)(19)(20)24) and the suppression of this production by ent-kaurene biosynthesis inhibitors such as CCC and phosphon D (18,20,24). Results from these early experiments on the sites and timing of GA production were conflicting, as were those on the identities and amounts of the GAs formed.…”

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confidence: 99%

“…Theoretically, GAs biosynthesized during grain development could be stored in the mature grain, either free or conjugated, causing a-amylase induction during germination. However, dry, mature barley embryos generally are reported to have no GA-like activity and no evidence for the release of GAs from conjugates has been found in barley caryopses (1,24).…”

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confidence: 99%

ent-Kaurene Biosynthesis in Germinating Barley (Hordeum vulgare L., cv Himalaya) Caryopses and Its Relation to α-Amylase Production

Großelindemann¹,

Je²,

Stöckl³

et al. 1991

Plant Physiol.

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ent-Kaurene biosynthesis as a prerequisite for gibberellin (GA) biosynthesis was studied in germinating Hordeum vulgare L., cv Himalaya caryopses and correlated, in time, with the appearance of a-amylase activity. The rate of ent-kaurene biosynthesis was estimated by inhibiting its further metabolism with plant growth retardants (triapenthenol or tetcyclacis) and measuring its accumulation by isotope dilution using combined gas chromatographymass spectrometry. In the inhibitor-treated caryopses, ent-kaurene accumulation began approximately 24 hours after imbibition and proceeded at a rate of about I to 2 picomoles per hour per caryopsis, depending on the batch of seeds. In the absence of inhibitor, ent-kaurene did not accumulate, indicating that it is normally turned over rapidly, presumably to further intermediates of the GA biosynthesis pathway and eventually to GAs. entKaurene accumulation occurred almost exclusively in the shoot, which is, therefore, probably the site of biosynthesis. a-Amylase production began between 30 and 36 hours after imbibition and, thus, correlated well with de novo GA biosynthesis, as estimated from ent-kaurene accumulation. However, inhibition of ent-kaurene oxidation by plant growth retardants did not reduce the aamylase production significantly, although it did reduce shoot elongation. We conclude that ent-kaurene is produced in the shoot and is continuously converted to GA, which is essential for normal shoot elongation, but not for the production of a-amylase in the aleurone layer.Paleg (15) and Yomo (23) discovered independently that GA3 could substitute for the embryo in initiating a-amylase formation in germinating barley grains. This finding and the demonstration by Chrispeels and Varner (4) that isolated aleurone layers produced a-amylase in response to added GA3 led to the well-known hypothesis that GA3 produced in the embryo diffuses to the aleurone tissue where it induces the formation of a-amylase and other hydrolytic enzymes. The induction of a-amylase in the aleurone layer in response to XSupported by grants from the Deutsche Forschungsgemeinschaft. 2Present address: Instand e.V., Johannes-Weyer-Str.

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“…The synthesis of c-amylase and of other hydrolases by the aleurone layers is specifically under the control of gibberellins (8) synthesized in the embryo (13,16,20). What factors control the transport of a-amylase and other hydrolases from the aleurone cells into the starchy endosperm?…”

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Characteristics of the Process of Enzyme Release from Secretory Plant Cells

Varner

Mense

1972

Plant Physiol.

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Secretion-the outward movement of molecules across the plasmalemma-of a-amylase by barley (Hordeum vulgare L cv. Himalaya) aleurone layers is an energy-dependent process that is not directly dependent upon protein synthesis or RNA synthesis and does not appear to be under the direct control of gibberellic acid or abscisic acid. Release-the movement of the secreted a-amylase molecules through the waUs into the sur. rounding medium-is apparently diffuion limited and is markedly dependent upon the presence of ions.At least as early as 1885 (Tangl, quoted by Haberlandt [10]), aleurone layers of the Gramineae were recognized as amylasesecreting tissues. Over the years this secretory activity of the alurone layers was verified by Haberlandt (10); disputed by Brown and Morris (4), Bruschi (5), Mann (14), and Bennion (1); reverified by Brown and Escombe (3), Griiss (9), and Schander (17); rediscovered by MacLeod and Millar (12) and Briggs (2); and re-reverified by Paleg (15), Yomo and linuma (19), and Varner and Chandra (18).The synthesis of c-amylase and of other hydrolases by the aleurone layers is specifically under the control of gibberellins (8) synthesized in the embryo (13,16,20). What factors control the transport of a-amylase and other hydrolases from the aleurone cells into the starchy endosperm?In the work reported here we have exploited our understanding of the aleurone tissue to study the movement of completed a-amylase molecules across the plasmalemma (secretion) and the diffusion of the secreted a-amylase through the walls into the surrounding medium (release).We have found that secretion is an energy-dependent process that is not directly dependent on protein synthesis or RNA synthesis and does not appear to be under the direct control of GA, or ABA. Release is probably diffusion limited and is markedly dependent on the presence of ions. METHODSBarley (Hordeum vulgare L. cv. Himalaya) aleurone layers were dissected from half-seeds that had been incubated for 3 days on moist sand and further incubated 19 to 24 hr in sterile

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Production of gibberellin-like substance in the embryo of barley during germination

Cited by 50 publications

References 7 publications

The ultrastructure of germinating barley seeds. I. Changes in the scutellum and the aleurone layer in Nordal barley

The ultrastructure of germinating barley seeds. I. Changes in the scutellum and the aleurone layer in Nordal barley

ent-Kaurene Biosynthesis in Germinating Barley (Hordeum vulgare L., cv Himalaya) Caryopses and Its Relation to α-Amylase Production

Characteristics of the Process of Enzyme Release from Secretory Plant Cells

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