Enzymes of Starch Metabolism in the Developing Rice Grain

Baun, Lyda C.; Palmiano, Evelyn P.; Perez, Consuelo M.; Juliano, B. O.

doi:10.1104/pp.46.3.429

Cited by 66 publications

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References 20 publications

(19 reference statements)

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“…The homogenate was centrifuged at 30,000g for 10 min at 4 C, and the crude supernatant fluid was used for the enzymic assays. R or debranching enzyme and a amylase were assayed colorimetrically with amylopectin /3 limit as substrate (3). The presence of R enzyme was verified using pullulan (Dr. W. J. Whelan, University of Miami) as substrate (19).…”

Section: Introductionmentioning

confidence: 99%

“…/3 Amylase was assayed by the colorimetric determination of maltose released (3). Phosphorylase was assayed by the amount of P, produced from glucose-l-P and amylopectin, according to Baun et al (3). Activities were expressed in AA or ,umoles per hour per grain.…”

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confidence: 99%

“…The presence of R enzyme was verified using pullulan (Dr. W. J. Whelan, University of Miami) as substrate (19). /3 Amylase was assayed by the colorimetric determination of maltose released (3). Phosphorylase was assayed by the amount of P, produced from glucose-l-P and amylopectin, according to Baun et al (3).…”

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confidence: 99%

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Biochemical Changes in the Rice Grain during Germination

1972

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Changes in the content of starch, protein, and RNA and in the activity of their hydrolases in the rice endosperm (Oryza sativa L., variety 1R8) were determined during the first week of germination without added nutrient both in the dark and in the light. Changes were generally more rapid in the dark than in the light. Oxygen uptake and RNase activity started to increase and the root protruded on the second day, followed by the coleoptile on the third day, and the primary leaf on the fourth day. ATP level was at a maximum on the fourth day.The activity of amylases and R enzyme increased progressively, but that of phosphorylase tended to decrease during starch degradation. A new a amylase isozyme band appeared during germination. Glucose was the major product of starch degradation. Sucrose, maltose, maltotriose, raffinose, and fructose were also detected. Protease activity reached a maximum on the fifth or sixth day and closely paralleled the increase in soluble amino N and soluble protein.In embryoless seed halves with 0.12 /tM gibberellin A3, peak protease activity occurred in 2.5 days and peak a amylase activity on the fifth day of incubation. The production of a amylase, protease, and R enzyme was inhibited by 40 uM cyclo. heximide, but only a amylase and R enzyme were inhibited by 20 ,ug/ml actinomycin D.Most studies on biochemical changes in the rice grain (Oryza sativa L.) during germination have been done on samples germinated in the dark (9,25,28). They involved an aspect of either starch or nitrogen metabolism. These studies used different varieties. so they cannot be compared. To obtain a comprehensive picture of the sequence of biochemical events occurring during germination, we studied the changes in activity of degradative enzymes and in their substrates in variety IR8 during the first week of germination both in the light and in the dark. The effect of inhibitors of the synthesis of protein and RNA on levels of a amylase and protease during the germination of embryoless seed halves in the presence of GA3 was also studied.MATERIALS AND METHODS Germination. Rice seeds (variety IR8) were sterilized by soaking them in 1% aqueous NaOCl for 20 min, washed, and 'Supported in part by Contract PH-43-67-726, National Institute of Arthritis and Metabolic Diseases, National Institutes of Health; this paper is in part the M.S. thesis of E. P. P. at the University of the Philippines College of Agriculture. steeped in distilled water for 24 hr. After soaking, the seeds were placed on moist filter paper in covered glass dishes and maintained at 30 C in the dark or in the diffuse light of the laboratory at 25 to 27 C. Germination schedules were staggered to permit harvesting of all the samples at the same time. The hull, roots, shoot, and scutellum were removed, and the degermed grains were freeze-dried, stored at -20 C, and used for all the subsequent analyses.Oxygen Uptake. Oxygen uptake was measured in duplicate from seeds germinated in light for 6 to 86 hr. Ten germinated grains were placed in Warburg fl...

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Biochemical Changes in the Rice Grain during Germination

1972

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“…The Pi released (Table I). In developing IR8 rice grains, the peak of the soluble protein level was found to occur about 10 days after flowering (3).…”

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Enzymes of Carbohydrate Metabolism in the Developing Rice Grain

Perez¹,

Perdon²,

Resurreccion³

et al. 1975

Plant Physiol.

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The levels of reducing and nonreducing sugars, starch, soluble protein, and selected enzymes involved in the metabolism of sucrose, glucose-l-P, and glucose nucleotides were assayed in dehulled developing rice grains (Oryza sativa L. line IR1541-76-3) during the first 3 weeks after flowering. The level of reducing sugars in the grain was highest 5 to 6 days after flowering. (6) suggested that, in developing barley, the UDP glucose formed from sucrose is first converted to glucose-l-P by UDP glucose pyrophosphorylase and then the glucose-l-P is converted to ADP glucose by ADP glucose pyrophosphorylase (Fig. 1)

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“…Starch synthetase and other enzymes involved in the conversion of sucrose to starch in the developing rice grain have been studied (4,21,22). As a continuation of these studies on starch accumulation, the qualitative and quantitative changes in the free sugars were studied in relation to starch accumulation in the developing grain of a waxy and nonwaxy rice.…”

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Free Sugars in Relation to Starch Accumulation in Developing Rice Grain

Singh¹,

Juliano²

1977

Plant Physiol.

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The changes in sugars (water-soluble carbohydrates) were studied in the developing grain of rice (Oryza sativa L., variety IR28 and IR29) in relation to the role of these sugars as precursors of ADP glucose in starch accumulation. The levels of total sugars, total reducing sugars and free glucose, sucrose and other nonreducing sugars, maltooligosaccharides, and total and nonsucrosyl fructose foflowed dosely the changes in the rate of starch accumulation, in both IR28 and 29; the peak value occurred 9 days after flowering. The The sucrose content of the extract was assayed by hydrolysis of the sucrose at 37 C for 20 min with invertase (Grade X from Candida utilis yeast, Sigma) and by measuring the glucose released by the glucose oxidase method (10). The content of nonreducing oligosaccharides other than sucrose was calculated from the difference between the total nonreducing sugars and the sucrose content. The anthrone assay at 50 C was used to measure fructose (17) and the content of nonsucrosyl fructose was calculated from the total fructose and sucrosyl fructose levels.Starch was extracted from the combined precipitated starch and insoluble residue with 52% HCl04 and analyzed by the anthrone method (12). The mean daily rate of starch accumulation for each sampling date represented the mean of the rates of starch accumulation before and after the sampling period (22). The amylose content was estimated by automated iodine colorimetry (18). RESULTSStarch started to accumulate 3 days after flowering and the rate of accumulation was almost linear from 5 to 9 days after flowering for both IR28 and IR29 (Fig. 1). The starch content of the grain became constant at 18 to 21 days after flowering. The weights of the IR28 grain and its starch content were greater than those of IR29. The weight of freeze-dried dehulled grain at maturity was 19.4 mg for IR28 and 17.3 mg for IR29. The accumulation curves for dry matter (grain weight) and starch for both rice varieties were similar. The amylose content of starch was 30.3% in the 3-day IR28 grain, 36.5% in the 5-day grain, 41.2% in the 7-day grain, and decreased to 36.7% in the mature grain. In contrast, the amylose content of IR29 starch decreased from 2.5 to 1.5% during grain development. The calculated mean daily rate of starch accumulation was maximum 7 days after flowering in both varieties at 1.78 mg/day for IR28 and 1.82 mg/day for IR29 (Fig. 2).

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Enzymes of Starch Metabolism in the Developing Rice Grain

Cited by 66 publications

References 20 publications

Biochemical Changes in the Rice Grain during Germination

Biochemical Changes in the Rice Grain during Germination

Enzymes of Carbohydrate Metabolism in the Developing Rice Grain

Free Sugars in Relation to Starch Accumulation in Developing Rice Grain

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