Signalling in Viroid Pathogenesis

Conejero, Vicente; Bellés, José María; García‐Breijo, Francisco J.; Garro, R.; Hernández-Yago, José; Rodrigo, Ismael; Vera, Pablo

doi:10.1007/978-3-642-74164-7_12

Cited by 26 publications

(34 citation statements)

References 65 publications

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“…The possible involvement of polyamines in the transduction of the viroid pathogenic signaling has also been hypothesized (14). The present work is the first experimental approach to test this hypothesis.…”

Section: Introductionmentioning

confidence: 78%

“…Viroid infection also causes an increased production of ethylene in the host plants (3)(4)(5)10) and the enhanced accumulation of the so-called PR proteins (6,11,23 (10). The viroid-like effects of silver ion has been attributed to its capacity to elicit ethylene biosynthesis in Gynura plants (10,14). Analogous effects are produced by ethephon (2-chloroethylphosphonic acid, an ethylene releasing compound) (10).…”

Section: Introductionmentioning

confidence: 99%

“…The viroid-like syndrome induced by AgNO3 in Gynura plants was prevented (4) by inhibitors of ethylene biosynthesis (aminooxyacetic acid or Co2+) (39,40) and ethylene action (norbornadiene) (30). Based on those findings, a view of viroid pathogenesis, in which viroid molecules are considered as pure replicative signals, has been proposed (14). In this hypothesis, viroids are elicitors of a general, ethylene-mediated response of the host plant.…”

Section: Introductionmentioning

confidence: 99%

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Polyamines in Plants Infected by Citrus Exocortis Viroid or Treated with Silver Ions and Ethephon

Bellés

Carbonell²,

Conejero³

1991

Plant Physiol.

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The levels of polyamines in leaves of Gynura aurantiaca DC and tomato, Lycoperskon esculentum Mill. cv Rutgers, infected with citrus exocortis viroid (CEVd) or treated with silver nitrate or ethephon (2-chloroethylphosphonic acid) were measured by HPLC in relation to development of symptoms. Previously it had been demonstrated that treatment of G. aurantiaca plants with silver nitrate or ethephon closely mimicked the effects of viroid infection in the plants. In the studies reported here, a marked decrease in putrescine level was observed in plants infected by CEVd or treated with silver ions or ethephon. There was no significant change in either spermidine or spermine levels. Treatment of G. aurantiaca plants with specific inhibitors of ethylene biosynthesis (aminoethoxyvinylglycine, Co2+) or ethylene action (norbomadiene) prevented the decrease of putrescine associated with silver nitrate treatment and had no effect on spermidine or spermine levels. The development of viroid-like symptoms, the production of associated pathogenesis-related proteins, and the rise in protease activity induced by silver nitrate, were all suppressed by exogenous application of putrescine. The decreased level of putrescine as an ethylene-mediated step in the transduction of the viroid and silver or ethephon signaling is discussed.

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Section: Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Polyamines in Plants Infected by Citrus Exocortis Viroid or Treated with Silver Ions and Ethephon

Bellés

Carbonell²,

Conejero³

1991

Plant Physiol.

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“…This is more relevant if we consider that the viroid elicited responses resemble those resulting from infection by more complex type of pathogens or different kind of stresses (7,8).…”

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confidence: 99%

“…It has been shown previously (8) that plants infected with viroids produce de novo synthesis of a set of host-encoded proteins termed pathogenesis-related (PR) 1 proteins. The function of some PR proteins as hydrolytic enzymes (e.g.…”

mentioning

confidence: 99%

Identification of a New Pathogen-induced Member of the Subtilisin-like Processing Protease Family from Plants

Tornero¹,

Conejero

Vera

1997

Journal of Biological Chemistry

132

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By using biochemical, immunological, and molecular strategies we have identified and cloned a cDNA encoding a protease from tomato (Lycopersicon esculentum) plants (P69B) that is part of a proteolytic system activated in the plant as a result of infection with citrus exocortis viroid. This new protease is closely related, in terms of amino acid sequence and structural organization, to the previously identified pathogenesis-related subtilisin-like protease (Tornero, P., Conejero, V., and Vera, P. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 6332-6337). The 745-residue amino acid sequence of P69B begins with a cleavable signal peptide, contains a prodomain and a 631-residue mature domain which is homologous to the catalytic modules of bacterial subtilisins and eukaryotic Kex2-like proteases. Within the catalytic domain, the essential Asp, His, and Ser residues that conform the catalytic triad of this family of proteases are conserved in P69B. Northern blot and reverse transcriptase-polymerase chain reaction analysis demonstrated widespread induced expression of the 2.5-kilobase hybridizing mRNA in plant tissues as a consequence of viroid infection. We propose that P69B is a member of a complex gene family of plant Kex2/subtilisin-like proteases presumably involved in a number of specific proteolytic events activated during pathogenesis in plants and that takes place in the extracellular matrix.Infection of plants with pathogens results in the induction of numerous host-specific biochemical responses, some of which are critical for the ability of the plant to withstand diseases (1). Physiological and pathological studies have examined diseased plants in the hope of uncovering the cause(s) of the pathogeninduced distress, and there is a plethora of studies describing the dramatic effect of pathogen infection upon different aspects of plant metabolism and catabolic disturbances (2-4). What is lacking, however, is a clear understanding of how different pathogens promote the often deleterious symptoms observed by switching on a common cascade of cellular events resulting in the disease syndrome and the accompanying resistant character to subsequent pathogenic attacks.Viroids are the smallest known plant infectious agents, made up of nude, circular, single-stranded RNA molecules of a few hundred nucleotides which do not code for any protein (5, 6), and thus they are an adequate model to analyze the physiological and molecular basis of plant responses to pathogen infection. This is more relevant if we consider that the viroid elicited responses resemble those resulting from infection by more complex type of pathogens or different kind of stresses (7,8).It has been shown previously (8) that plants infected with viroids produce de novo synthesis of a set of host-encoded proteins termed pathogenesis-related (PR) 1 proteins. The function of some PR proteins as hydrolytic enzymes (e.g. chitinases or ␤-1,3-glucanases) has been demonstrated in many plant species irrespective of the nature of the attacking pathogen, and they appea...

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