Ultrastructural Changes in the Walls of Ripening Avocados: Transmission, Scanning, and Freeze Fracture Microscopy

Platt‐Aloia, K. A.; Thomson, W. W.; Young, Roy E.

doi:10.1086/337169

Cited by 53 publications

(38 citation statements)

References 24 publications

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“…In the case of avocados, detailed ultrastructural studies have been made of the cell wall (Platt-Aloia et al 1980) and of the cell wall contents (Platt-Aloia and Thomson 1981) in ripening fruit. During ripening, it was found that the middle lamella begins to disappear, with pectin removal from the matrix of the cell walls.…”

Section: B Structural Changesmentioning

confidence: 99%

“…It was found that the enzyme is a (1 -cu4)-/3-D-glucanase, and that the activity is limited to hydrolysing /3-D-glucans of four or more glucosyl residues. These authors therefore contend that the solubilization of the cell walls during softening as seen by Platt-Aloia et al (1980) cannot be due to cellulase alone, and they propose a different role forcellulase. Hatfield and Nevins (1986) consider that xyloglucans or cellulose fibrils may be hydrolysed, which would be consistent with microscopic observations of cellulose xyloglucans, or cellulose fibrils may be hydrolysed, which would be consistent with microscopic observations of cellulose fibrillar changes.…”

Section: Enzymesmentioning

confidence: 99%

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Avocado Fruit Development and Ripening Physiology

Bower

Cutting

1988

Horticultural Reviews

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Section: B Structural Changesmentioning

confidence: 99%

Section: Enzymesmentioning

confidence: 99%

Avocado Fruit Development and Ripening Physiology

Bower

Cutting

1988

Horticultural Reviews

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“…Ripening of avocado fruit is accompanied by softening of the fruit which is believed to be due to an extensive breakdown of its cell wall (20). Fruit softening is associated with an increase in the activities of hydrolytic enzymes such as cellulase and polygalacturonase (1,6,14,19).…”

mentioning

confidence: 99%

“…Fruit softening is associated with an increase in the activities of hydrolytic enzymes such as cellulase and polygalacturonase (1,6,14,19). Although an increase in avocado cellulase activity correlates well with softening (1) and changes in the structural integrity of the cell wall (19,20), elucidation of its role in vivo is far from complete (12).…”

mentioning

confidence: 99%

Cellulase Occurs in Multiple Active Forms in Ripe Avocado Fruit Mesocarp

Kanellis¹,

Kalaitzis²

1992

Plant Physiol.

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The existence of multiple forms of avocado (Persea amerkana Mill. cv Hass) cellulase in crude protein extracts of ripe avocado fruit is reported. Cellulase was separated into at least 11 multiple forms by native isoelectric focusing in the pH range between 4 and 7 and visualized by both activity staining using Congo red and immunostaining. The enzyme components were acidic proteins with isoelectric points in the range of pH 5.10 to 6.80, the predominant forms having isoelectric points of 5.60, 5.80, 5.95, and 6.20. All 11 forms were immunologically related with molecular masses of 54 kilodaltons.

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“…Softening in avocado fruits is accompanied by an extensive breakdown of the cell wall (22), which is associated with an increase in the activities of hydrolytic enzymes such as cellulase, polygalacturonase, and acid phosphatase (3,21,23). Information concerning the synthesis and regulation of polygalacturonase and acid phosphatase during avocado ripening is very limited.…”

mentioning

confidence: 99%

Hydrolytic Enzyme Activities and Protein Pattern of Avocado Fruit Ripened in Air and in Low Oxygen, with and without Ethylene

Kanellis¹,

Solomos²,

Mattoo³

1989

Plant Physiol.

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The effect of 2.5% 02 atmosphere with and without ethylene on the activities of hydrolytic enzymes associated with cell walls, and total protein profile during ripening of avocado fruits (Persea americana Mill., cv Hass) were investigated. The low 2.5% 02 atmosphere prevented the rise in the activities of cellulase, polygalacturonase, and acid phosphatase in avocado fruits whose ripening was initiated with ethylene. Addition of 100 microliters per liter ethylene to low 02 atmosphere did not alter these suppressive effects of 2.5% 02. Furthermore, 2.5% 02 atmosphere delayed the development of a number of polypeptides that appear during ripening of avocado fruits while at the same time new polypeptides accumulated. The composition of the extraction buffer and its pH greatly affected the recovery of cellulase activity and its total immunoreactive protein.Softening is a common and very pronounced feature that attends ripening of fleshy fruits. Softening in avocado fruits is accompanied by an extensive breakdown of the cell wall (22), which is associated with an increase in the activities of hydrolytic enzymes such as cellulase, polygalacturonase, and acid phosphatase (3,21,23). Information concerning the synthesis and regulation of polygalacturonase and acid phosphatase during avocado ripening is very limited. Although a cardinal role for cellulase enzyme in avocado softening has been suggested (3, 21), elucidation of its role in vivo is far from complete (12). However, increase in cellulase activity during ripening of avocado closely correlates with an increase in the levels of cellulase protein and that of cellulase mRNA (9,28,29), indicating a pretranslational regulation of cellulase synthesis (9).It is well established that 02 levels below those in air retard the rate of ripening, and softening of climacteric fruits (13)(14)(15) retarding effects of low 02 on fruit softening reflect a diminution of ethylene action.In the present communication we report the effect of 2.5% 02, with and without ethylene, on both the changes in the activities of the hydrolytic enzymes that may play a cardinal role in cell wall degradation and the steady state protein pattern during ripening. MATERIALS AND METHODS Plant MaterialFreshly harvested avocado fruits (Persea americana Mill., cv Hass) were air shipped overnight from University of California, Riverside, to the laboratory at College Park, MD. Alternatively, preclimacteric avocado fruits were purchased from the local wholesale market. Individual fruits were enclosed in glass jars of appropriate size with minimum void space, and kept at 20°C under a steady flow of 50 to 60 ml. min-' humidified C02-free air. The flow rates were selected to ensure that CO2 accumulation did not exceed 0.3%. Carbon dioxide and ethylene production were measured daily by a gas chromatograph equipped with either thermal conductivity (CO2) or flame ionization (ethylene) detectors. Initially, CO2 and ethylene levels were measured to ensure the stage of ripeness of the fruits. Ripening of the frui...

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Ultrastructural Changes in the Walls of Ripening Avocados: Transmission, Scanning, and Freeze Fracture Microscopy

Cited by 53 publications

References 24 publications

Avocado Fruit Development and Ripening Physiology

Avocado Fruit Development and Ripening Physiology

Cellulase Occurs in Multiple Active Forms in Ripe Avocado Fruit Mesocarp

Hydrolytic Enzyme Activities and Protein Pattern of Avocado Fruit Ripened in Air and in Low Oxygen, with and without Ethylene

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