The Role of Cullulase in the Abscission of Citrus Leaves and Fruits in Relation to Exogenous Treatments With Growth Regulators

Gören, R.; Teitelbaum, G.; Ratner, Ariel

doi:10.17660/actahortic.1973.34.48

Cited by 17 publications

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“…The present investigation confirmed earlier data (5,13) that the activity of cellulase soluble in buffer in citrus is closely correlated with abscission, and that this activity is more evident in the tissue proximal to the separation line. It also demonstrated LITERATURE CITED…”

Section: Discussionsupporting

confidence: 92%

The Effects of pH, Ionic Strength, and Ethylene on the Extraction of Cellulase from Abscission Zones of Citrus Leaf Explants

Huberman¹,

Gören²,

Birk³

1975

Plant Physiol.

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The solubility of cellulase extracted from the abscission zones of citrus leaf explants (Citrus sinensis L. Osbeck) in sodium phosphate buffer depends on the pH of the extracting solution and, to a lesser extent, on the ionic strength. By increasing molarity from 0.01 to 0.16, the solubility of cellulase increased from 51% to 89% at pH 6.1 and from 70% to 98% at pH 7. In all cases, residual cellulase was further extracted from the pellet by buffer containing 1 M NaCl. Most of the enzymic activity was found in tissues proximal to the separation line, and activity of the cellulase which was soluble in phosphate buffer was closely correlated with abscission at both pH values. When extraction of cellulase at pH 6.1 with phosphate buffer was followed by a reextraction of the pellet with buffer containing 1 M NaCl, the activity of the cellulase soluble in the fortified buffer was also correlated with abscission. Pretreatment of explants with ethylene increased the solubility of cellulase in the phosphate buffer regardless of the pH used at the first extraction. Lewis and Varner (8) distinguished between two types of cellulase, soluble and residual, in explants of Phaseolus vulgaris. The first refers to the enzyme soluble in 20 mm phosphate buffer at pH 6.1, and the latter, to enzyme that can only be obtained from the pellet by means of reextraction in buffer containing 1 M NaCl. Later on, the two cellulases were designated as isozyme cellulase 4.5 and 9.5, respectively, according to their isoelectric points (7). In most studies on the role of cellulase in abscission (e.g., 1, 5, 6, 13), the enzyme activity which was found to be related to abscission was extracted in unfortified 0.05 to 0.1 M phosphate buffer at pH 7. Because Lewis and Varner (8) extracted soluble cellulase with a buffer of lower pH and molarity, it seemed necessary to resolve the different results obtained using the two sets of extraction conditions. These differences were that under conditions of lower pH and molarity, abscission was correlated with residual cellulase rather than soluble cellulase activity. Nevertheless, after treating explants with either ethylene or Ethephon, the increase was primarily in soluble cellulase (8). Thus, the following questions have been raised: Is the fact that no correlation could be established between the activity of soluble cellulase and abscission (8) related to the lower pH and molarity of the extracting buffer?Moreover, can reextraction of the pellet with buffer containing 1 M NaCl promote further extraction of a specific cellulase fraction? Does ethylene affect the extractability of cellulase by the phosphate buffer?The present investigation attempts to provide answers to these questions. MATERIALS AND METHODSPlant Material. Four-to 10-month-old leaves were picked from 40-year-old Shamouti orange (Citrus sinensis L. Osbeck) trees and transferred to the laboratory in moist chambers. Twenty-mm long explants (10 mm from the petiole and 10 mm from the midrib of the leaf blade) were excised and washed in r...

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Section: Discussionsupporting

confidence: 92%

The Effects of pH, Ionic Strength, and Ethylene on the Extraction of Cellulase from Abscission Zones of Citrus Leaf Explants

Huberman¹,

Gören²,

Birk³

1975

Plant Physiol.

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“…Since Horton and Osborne published their work (1967), it has been clearly demonstrated that cellulase is involved in leaf abscission in various piants, including citrus (Abeies 1969, Ratner et al, 1969, Lewis and Varner 1970, Abeles and Leather 1971, Lewis et at 1972, Reid et al, 1974. Recently it has been reported that cellulase is active in separation processes of citrus fruits as well (Poilard and Biggs 1970, Young 1972, Goren et al 1973, Rasmussen 1973). Rogers and Hurley (1971) reported an activity of a macerating factor in button tissues of Valencia oranges, which they measured by a pectinase bioassay, and concluded that a pectinase may have a role in the abscissioo of mature fruits.…”

Section: Ititroductionmentioning

confidence: 99%

The Role of Cellulase and Polygalacturonase in Abscission of Young and Mature Shamouti Orange Fruits

Greenberg

Gören

Riov

1975

Physiologia Plantarum

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During the first eight weeks after setting young citrus fruits gradually lose their ability to abscise at the abscission zone between the stem and the pedicel; in fruits older than eight weeks abscission occurs at the calyx area. The activity of cellulase and polygalacturonase in the two abscission zones was markedly increased before and during abscission, and was localized mainly in the abscission zone. Ethylene accelerated the increase in enzymic activity after an 8‐ to 10‐h lag period; 2,4‐D delayed abscission and enzymic activity when applied during the first 24 h after excision. During this period 2,4‐D also partly suppressed the enhancing effect of ethylene. Early application of cyclo‐heximide inhibited the formation of the enzymes and thus abscission was delayed to a certain extent. Although there are some indications that the relationship between enzymic activity and abscission is a complex one, the data presented indicate that cellulase and polygalacturonase play a significant role in abscission of citrus fruits at various developmental stages. Both enzymes act almost simultaneously and are equally controlled by ethylene and 2,4‐D.

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“…Some polygalacturonases (PGases) related to the softening of peach fruits have also been studied [11,29]. Despite the economic relevance of abscission in fruits, this phenomenon has mainly been studied in leaves of such plants as bean [23 ], tomato [36], elder [33] and citrus [16]. The knowledge of the physiological and molecular bases of abscission in peach is important in relation to immature and pre-harvest fruit drop control.…”

Section: Introductionmentioning

confidence: 99%

Cellulase and polygalacturonase involvement in the abscission of leaf and fruit explants of peach

et al. 1992

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Ethylene-induced abscission in leaf and fruit explants of peach involves different enzymes. In leaves abscission is accompanied by increased occurrence of cellulase forms differing in isoelectric point (pI 6.5 and 9.5). A polypeptide with a molecular mass of 51 kDa gives in a western blot a strong cross-reaction with an antibody raised against a maturation cellulase from avocado fruit. Cellulase activity is also found in abscising fruit explants but the amount is very low compared to that of the leaf explants. A northern analysis with a cellulase clone from avocado reveals the presence of two hybridizing mRNAs with a size of 2.2 kb and 1.8 kb, respectively. The steady-state level of the 2.2 kb mRNA is significantly increased by treatment with ethylene. Polygalacturonases are not detected in abscising leaves, but are strongly induced by ethylene in fruit explants. Of the three forms found, two are exopolygalacturonases while the third is an endoenzyme. Ethylene activates preferentially the endoenzyme and the basic exoenzyme but depresses the acid exopolygalacturonases. A northern analysis carried out with a cDNA coding for tomato endopolygalacturonase shows hybridization only with one endopolygalacturonase mRNA form in the fruit abscission zone. Treatment with ethylene causes an increase in the steady-state level of this mRNA. The differences in the enzyme patterns observed in fruit and leaf abscission zones and a differential enzyme induction suggest the feasibility to regulate fruit abscission in peach with the aid of antisense RNA genes.

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The Role of Cullulase in the Abscission of Citrus Leaves and Fruits in Relation to Exogenous Treatments With Growth Regulators

Cited by 17 publications

References 0 publications

The Effects of pH, Ionic Strength, and Ethylene on the Extraction of Cellulase from Abscission Zones of Citrus Leaf Explants

The Effects of pH, Ionic Strength, and Ethylene on the Extraction of Cellulase from Abscission Zones of Citrus Leaf Explants

The Role of Cellulase and Polygalacturonase in Abscission of Young and Mature Shamouti Orange Fruits

Cellulase and polygalacturonase involvement in the abscission of leaf and fruit explants of peach

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