Research articleEthylene induced cotton leaf abscission is associated with higher expression of cellulase (GhCel1) and increased activities of ethylene biosynthesis enzymes in abscission zone
Introduction
Abscission is the process by which plants shed organs from the parent body in response to developmental cues or to adapt to various environmental stresses including pathogen attack [26], [31]. The signal that promotes abscission has been widely recognized as the gaseous plant hormone ethylene [1], [37]. The role of ethylene in abscission was deduced by the use of chemical agents such as norbornadiene, silver ions or 1-MCP that block ethylene action [10], [40], [41] or mutants, which are deficient in ethylene perception and response [7]. Organ separation is accomplished by degradation of the cell wall and middle lamella to form a fracture plane between the abscising organ and the parent plant. Although the precise sequence of events that bring about cell wall degradation is unclear, biochemical and molecular studies indicate that an increase in the activities of hydrolytic enzymes such as glucanases [5], [38] and polygalacturanases [14], [18] and proteins such as expansins [4] play a major role in the process of abscission.
An increase in cellulase (endo-1,4-β-d-glucanase) activity has been noted in leaf abscission zones (LAZ) [20], [40], fruit abscission zones [15], [17], ripening fruits [24] senescing styles and anthers [34] and during adventitious root initiation [23]. The isoelectric points (pIs) of many of these cellulases differ from each other, which suggest that each may have distinct cellular function. Although cellulases have been identified and cloned from the abscission zones of several different sources, information relating to its role in leaf abscission is limited [31].
In the present study we have investigated petiole abscission in cotton using biochemical and molecular tools. The activities of cellulase and ethylene biosynthesis enzymes have been measured in LAZ and correlated with the progression of petiole separation. A leaf abscission specific cDNA has been cloned and characterized for the first time from cotton and accumulation of mRNA in abscission zones studied in the presence and absence of 1-MCP, an ethylene action inhibitor. The results of this study gain significance due to commercial importance of cotton leaf abscission.
Section snippets
Plant material and treatments
Seeds of cotton (Gossypium hirusutum var RST-39) were germinated in glasshouse under controlled temperature (32 ± 3 °C) for 12–15 days until the primary leaves were fully expanded and the secondary pinnate leaf was just beginning to open. At this time, the leaf blades for the primary leaves were removed and plants harvested by cutting 1 cm above the soil. Twenty-five explants, each of 8–10 cm long, were surface sterilized using bleach (10% v/v) for 5 min, washed 3–4 times with distilled water and kept
Changes in break strength during leaf abscission
In order to elucidate the effect of ethylene on the cell separation process the force (beak strength) required to pull the petiole away from the stem was measured in explants every 12 h after exposure to ethylene (Fig. 1). The break strength decreased gradually from 26.9 gr equivalent prior to ethylene exposure (0 h) to 1.2 gr equivalent after 48 h exposure to 10 μl/l ethylene. To establish whether ethylene plays a direct role in cotton leaf abscission, explants were treated with 1-MCP before
Discussion
Organ abscission is believed to be a highly coordinated process where the plant hormone ethylene plays an important role in regulating the breakdown of the cell wall of a layer of cells in the abscission zone. It is well documented that during leaf, flower and fruit abscission cell wall degradation is associated with an increase in the activity of several hydrolytic enzymes [14], [16], [38] and expansins [4]. These enzymes and proteins may either contribute to the cell separation process or
Acknowledgements
The authors are grateful to the Department of Science and Technology, New Delhi for financial support to carry out the work. Senior Research Fellowship to AM and Research Associate ship to SK from CSIR, India is acknowledged. Authors are thankful to Mr. V.K. Lal and Mr. Alok Saxena for scanning electron microscopy work.
References (41)
- et al.
Cellulases in Phaseolus vulgaris
Methods Enzymol.
(1988) - et al.
Changes in activities of cell wall hydrolases during ethylene induced ripening in banana: effect of 1-MCP, ABA and IAA
Postharvest Biol. Biotech.
(2004) - et al.
The Purification of an anther cellulase (β (1: 4) 4-glucan hydrolase) from Lathyrus odoratus L. and its relationship to the similar enzyme found in abscission zones
Plant Sci.
(1990) - et al.
Ethylene in Plant Biology
(1992) - et al.
Functional genomics of cell elongation in developing cotton fibers
Plant Mol. Biol.
(2006) - et al.
A simple procedure for the isolation of high quality RNA from ripening banana fruit
Plant Mol. Biol. Rep.
(2000) - et al.
Changes in expansin activity and gene expression during ethylene-promoted leaflet abscission in Sambucus nigra
J. Exp. Bot.
(2005) - et al.
Antisense suppression of tomato endo-1,4-beta-glucanase Cel2 mRNA accumulation increases the force required to break fruit abscission zones but does not affect fruit softening
Plant Mol. Biol.
(1999) - et al.
Site-directed mutagenesis of essential carboxulic residues in Clostridium thermocellum endoglucanase CelD
J. Biol. Chem.
(1992) - et al.
Characterization of a non-abscission mutant in Lupinus angustifolius. I. Genetic and structural aspects
Am. J. Bot.
(2001)
Multiple sequence alignment with hierarchical clustering
Nucleic Acids Res.
Temporal and spatial expression of mRNAs encoding pathogenesis-related proteins during ethylene promoted leaflet abscission in Sambucus nigra
Plant Cell. Environ.
Abscission-inducing properties of methyl jasmonate, ABA, and ABA-methyl ester and their interactions with ethephone, AgNO3, and malformin
J. Plant Growth Regul.
Occurrence and localization of 9.5 cellulase in abscising and nonabscising tissues
Plant Cell
The use of immunological methods to study the activity of cellulase isoenzymes (β-1,4-glucan 4-glucan hydrolase) in bean leaf abscission
Plant Cell. Environ.
Temporal and spatial expression of a polygalacturonase during leaf and flower abscission in oilseed rape and Arabidopsis
Plant Physiol.
The role of cellulase and Polygalacturonase in abscission of young and mature Shamouti orange fruits
Physiol. Plant
Ethylene, the natural regulator of leaf abscission
Nature
Molecular characterization of a tomato endo-β-1,4-glucanase gene expressed in mature pistils, abscission zones and fruit
Plant Cell. Physiol.
Cloning of a tomato polygalacturonase expressed in abscission
Plant Mol. Biol.
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