Citrus leaf abscission. Regulatory role of exogenous auxin and ethylene on peroxidases and endogenous growth substances

Gaspar, Th.; Gören, R.; Huberman, M.; Dubucq, M.

doi:10.1111/j.1365-3040.1978.tb00765.x

Cited by 28 publications

(11 citation statements)

References 30 publications

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“…We expect, however, that even this well-studied ethylene response will show the involvement of free radical-mediated CW breakage upon closer investigation. The upregulation of preformed leaf abscission zone peroxidases in response to ethylene treatment in citrus, for instance, may point to such a role [53]. …”

Section: Perspectives and Future Directionsmentioning

confidence: 99%

Controlled free radical attack in the apoplast: A hypothesis for roles of O, N and S species in regulatory and polysaccharide cleavage events during rapid abscission by Azolla

et al. 2014

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Shedding of organs by abscission is a key terminal step in plant development and stress responses. Cell wall (CW) loosening at the abscission zone can occur through a combination chain breakage of apoplastic polysaccharides and tension release of cellulose microfibrils. Two distinctly regulated abscission cleavage events are amenable to study in small water ferns of the genus Azolla; one is a rapid abscission induced by environmental stimuli such as heat or chemicals, and the other is an ethylene-induced process occurring more slowly through the action of hydrolytic enzymes. Although free radicals are suggested to be involved in the induction of rapid root abscission, its mechanism is not fully understood. The apoplast contains peroxidases, metal-binding proteins and phenolic compounds that potentially generate free radicals from H2O2 to cleave polysaccharides in the CW and middle lamella. Effects of various thiol-reactive agents implicate the action of apoplastic peroxidases having accessible cysteine thiols in rapid abscission. The Ca2+ dependency of rapid abscission may reflect the stabilization Ca2+ confers to peroxidase structure and binding to pectin. To spur further investigation, we present a hypothetical model for small signaling molecules H2O2 and NO and their derivatives in regulating, via modification of putative protein thiols, free radical attack of apoplastic polysaccharides.

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Section: Perspectives and Future Directionsmentioning

confidence: 99%

Controlled free radical attack in the apoplast: A hypothesis for roles of O, N and S species in regulatory and polysaccharide cleavage events during rapid abscission by Azolla

et al. 2014

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“…One unit of peroxidase activity is defined as that amount of tetraguaiacol formed which increases A420 by 0.1 per min (on fresh weight or protein basis). Peroxidase isoenzyme patterns were determined by vertical starch gel electrophoresis according to Gaspar (see 10). Electrophoresis was run for 3 to 4 h at 300 v and 0°C.…”

mentioning

confidence: 99%

Growth and Metabolic Activity of Lemon Juice Vesicle Explants in Vitro

Altman¹,

Gulsen²,

Gören³

1982

Plant Physiol.

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Actively growing juice-vesicle explants, established from smaDl lemon (Cits lmon L. Burm. f. var. 'Eureka') fruits, were cultured in vitro on defined media. The juice vesicles continued to enlarge in culture for several months, without caDlus proliferation, and their initial growth was promoted by indoleacetic acid, gibberellic acid, and N-benzyladenine.The metabolic competence of the explants, and its relevance to whole fruit development, was further investigated. Juice vesicles continued to accumulate protein on al media, for at least 16 days, but sugars did not change much during culture. Acid invertase increased dramatically during the first days of culture, and its specific activity was markedly promoted by indoleacetic acid, and to a lesser degree by gibberelic acid. Total peroxidase ofjuice vesicles increased progressively up to the 11th day of culture, and its specific activity was promoted by all three hormones, especially by N-benzyladenine. Explant growth was accompanied by appearance of several cathodic and anodic isoperoxidases.The results suggest that the study of this unique juice vesicle system may contribute to a better understanding of fruit development.Apart from their extensive use in rapid clonal propagation and in genetic research (25), plant tissue culture methods may be useful in development and physiological studies. The advantage of in vitro tissue and organ culture stems from the possibility of minimizing undefined variables and carefully controlling medium composition, and from the continuous availability of plant material. Such in vitro studies are, however, dependent on: (a) establishment of a long term growing culture; (b) elucidation of the physiological and metabolic competence in vitro; and (c) a substantial resemblance between physiological and biochemical patterns of tissue cultures and those of their parent, intact, plants.Our earlier studies have established the suitability of tissue culture studies with citrus bud explants (1, 2). We found it desirable to extend these findings to fruits and fruit explants. Three different in vitro culture systems have been attempted in the past for the study of fruit development: the culture of floral buds, of fertilized ovules and ovaries, and of fruit explants (3,17,21,23,28,30 Former studies with citrus fruit explants, employing either separated juice vesicles (7, 17) or peel tissues (7, 9, 21), all resulted in callus proliferation. Thus, they are irrelevant for the study of the unique physiology ofjuice vesicles. Recently, we were able to culture juice vesicles with potentially unlimited and undisturbed growth (15). In the following, we described the in vitro growth of lemon juice vesicle explants and their metabolic competence as evidenced by protein and sugar accumulation and the activities of invertase and peroxidase.MATERIALS AND METHODS Plant Material. Small fruits (about 12.5 mm in diameter) were harvested during December-January from orchard-grown 15-yearold 'Eureka' lemon (Citrus limon L.Burm. f., var. 'Eureka'). The fru...

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“…Fe^"^ (Yang & Pratt. 1978;Lau & Yang, 1976) and elemental Hg (Goren & Siegel. 1976) are known to promote C2H4 formation, while Co^+ and Ni^^ (Lau & Yang.…”

Section: Discussionmentioning

confidence: 99%

“…Similar kinetics has been reported for C2H4 formation induced by SO2 (Peiser & Yang, 1979) or Cu^^ (Lau & Yang, 1976). Continuous stimulation over 50 h was found in the case of elemental Hg (Goren & Siegel, 1976).…”

Section: Discussionmentioning

confidence: 99%