Synthesis of Cellulase during Abscission of Phaseolus vulgaris Leaf Explants
TL;DR: When abscission in leaf explants from Phaseolus vulgaris, cultivar Red Kidney, was allowed to proceed while the explants were in (2)H(2)O, a 1.25% increase in the buoyant density of cellulase in a cesium chloride gradient was observed, indicating that the increase in cellulase activity during abscissions is a result of the synthesis of new protein.
Abstract: When abscission in leaf explants from Phaseolus vulgaris, cultivar Red Kidney, was allowed to proceed while the explants were in (2)H(2)O, a 1.25% increase in the buoyant density of cellulase in a cesium chloride gradient was observed. These data indicate that the increase in cellulase activity during abscission is a result of the synthesis of new protein. Two differentially soluble forms of cellulase are present in the abscission zone. The form which is soluble only in a high salt buffer seems more closely related to the abscission process than the form which is soluble in dilute buffer. The correlation between changes in pull force and increase in cellulase activity and the effects of several hormones on cellulase activity are discussed.
Citations
More filters
TL;DR: This review details what the authors know of the signals that lead to the differentiation of zone cells; the environmental signals that promote cell separation, and the possible intracellular signalling events that culminate in organ shedding.
Abstract: Abscission is the term used to describe the process of natural separation of organs from the parent plant. This may be part of the highly programmed development of a plant, or in response to environmental stress. It enables temperate plants to overwinter and hence survive, but in agricultural or horticultural environments premature abscission can lead to significant crop losses. Abscission is the culmination of changes in gene expression, which result in the loosening of adjacent cell walls within the zone and subsequent cell separation. For many years it has been recognized that the balance between the plant hormones ethylene and auxin determine where, and when, separation takes place. As we begin to understand the mechanisms by which plant growth regulator signals are perceived and transduced, we can begin to understand how the process of abscission itself may be induced and regulated. This review details what we know of the signals that lead to the differentiation of zone cells; the environmental signals that promote cell separation, and the possible intracellular signalling events that culminate in organ shedding.
324 citations
TL;DR: A substantial body of literature supports the involvement of ethylene in abscission of leaves, flowers and flower parts, and fruit, and endogenous ethylene production increases before abscissions, while in others a change in ethylene sensitivity can be demonstrated.
Abstract: A substantial body of literature supports the involvement of ethylene in abscission of leaves, flowers and flower parts, and fruit. Exogenous ethylene accelerates abscission in many, but not all, abscising plant systems. In some cases, endogenous ethylene production increases before abscission, while in others a change in ethylene sensitivity can be demonstrated. Ethylene interacts with auxin in regulating abscission, particularly in leaves and fruit. Ethylene has been shown to regulate expression of genes involved in cell separation, including cellulases and pectinases. Such regulation has been demonstrated at the level of mRNA abundance, but post-transcriptional regulation may also be important.
295 citations
TL;DR: The procedure enabled 30% of the tobacco cells to form protoplasts, 80% of which regenerated cell walls in 4 days and 40% resumed cell division activity when returned to cell culture medium.
Abstract: A systematic evaluation disclosed the following conditions to be optimum for the isolation of viable protoplasts from cultured cells of Nicotiana tabacum L. `Bright Yellow9 grown in liquid suspensions: ( a ) the cell culture in the early phase of cell number increase, ( b ) an enzyme mixture of 1% cellulase “Onozuka” and 0.2% Macerozyme, ( c ) an enzyme solution pH of 4.7 or 5.7, ( d ) a 2- to 3-hr incubation period, ( e ) 5 ml of enzyme solution per 500 mg cells and contained in a 50-ml Delong flask, ( f ) agitation on a gyrotory shaker at 50 rpm, and ( g ) 0.3 to 0.8 m mannitol as osmoticum in the cell enzyme mixture. The incubation temperature may be varied from 22 to 37 C. The procedure enabled 30% of the tobacco cells to form protoplasts, 80% of which regenerated cell walls in 4 days and 40% resumed cell division activity when returned to cell culture medium.
251 citations
TL;DR: This work has identified five novel dab (delayed floral organ abscission) mutants in Arabidopsis and compared these mutants with the ethylene-insensitive mutants etr1-1 and ein2-1 to determine if ethylene is an essential component of the abscissions process and finds that although ethylene can accelerate abscmission under many conditions, the perception of ethylene was not essential.
Abstract: Abscission is an important developmental process in the life cycle of the plant, regulating the detachment of organs from the main body of the plant. This mechanism can be initiated in response to environmental cues such as disease or pathogen, or it can be a programmed shedding of organs that no longer provide essential functions to the plant. We have identified five novel dab (delayed floral organ abscission) mutants (dab1-1, dab2-1, dab3-1, dab3-2, and dab3-3) in Arabidopsis. These mutants each display unique anatomical and physiological characteristics and are governed by three independent loci. Scanning electron microscopy shows delayed development of the flattened fracture plane in some mutants and irregular elongation in the cells of the fracture plane in other mutants. The anatomical observations are also supported by breakstrength measurements that show high breakstrength associated with broken cells, moderate levels for the flattened fracture plane, and low levels associated with the initial rounding of cells. In addition, observations on the expression patterns in the abscission zone of cell wall hydrolytic enzymes, chitinase and cellulose, show altered patterns in the mutants. Last, we have compared these mutants with the ethylene-insensitive mutants etr1-1 and ein2-1 to determine if ethylene is an essential component of the abscission process and find that although ethylene can accelerate abscission under many conditions, the perception of ethylene is not essential. The role of the dab genes and the ethylene response genes during the abscission process is discussed.
188 citations
TL;DR: The physiological evidence indicates a role of both polygalacturonase and cellulase in cell wall dissolution, whilst the role of other cell wall degrading enzymes is still unknown and the physiological processes occurring in the walls of the separating cells should be distinguished from those relating to defence against microbial intrusion.
Abstract: The abscission of inflorescences, flowers, petals, sepals, styles, and stamens is discussed, with emphasis on the anatomy and ultrastructure of the abscission zones, and the role of cell wall degrading enzymes and hormonal control Shedding of these parts is usually due to cell wall dissolution, but abscission of petals, stamens, and styles in some species occurs due to the forces generated by the growing fruit Flower abscission is clearly regulated by ethylene, whilst auxins apparently decrease the sensitivity to ethylene Petal, style and stamen abscission also seems to be controlled by endogenous ethylene Auxin is apparently involved in abscission of styles and stamens, but in petals its role is at yet unclear The ultrastructural data indicate high protein synthesis and high secretory activity of material toward cell walls of abscission zone cells The physiological evidence indicates a role of both polygalacturonase and cellulase in cell wall dissolution, whilst the role of other cell wall degrading enzymes is still unknown The physiological processes occurring in the walls of the separating cells should be distinguished from those relating to defence against microbial intrusion, such as deposition of lignin and suberin and tylose formation Experimentation using mutants and transgenic plants may aid in separating these processes Sequencing of the isoenzymes specific for the abscission zone and a search for abscission zone-specific promoters seems a requirement for the successful evaluation of the enzymes involved in cell wall degradation
184 citations
References
More filters
TL;DR: In this paper, the reliability of the various Somogyi-Shaffer-Hartmann (SHH) copper reagents for glucose determination in biological material has been established, which can be accomplished by omission of the iodide and iodate in their preparation, since these interfere with the molybdate color reagents.
10,346 citations
TL;DR: A modification of the naphthalene-dioxane-PPO liquid scintillator has been described which will allow up to 3.0 ml of an aqueous solution to be counted as mentioned in this paper.
7,634 citations
TL;DR: Before abscissions, high cellulase activity develops in cells of the abscission zone, suggesting that this enzyme plays an important part in cell separation.
Abstract: Before abscission, high cellulase activity develops in cells of the abscission zone, suggesting that this enzyme plays an important part in cell separation. Cellulase activity rises in response to senescence of tissue distal to the zone; distal senescence is regulated by auxin and ethylene.
170 citations
142 citations