ACC Synthesis as the Activated Step Responsible for the Rise of Ethylene Production Accompanying Citrus Exocortis Viroid Infection in Tomato Plants

Citrus exocortis viroid (CEVd) is known to cause different symptoms in citrus trees, and its mechanism of infection has been studied in tomato as an experimental host, producing ribosomal stress on these plants. Some of the symptoms caused by CEVd in tomato plants resemble those produced by the phytohormone ethylene. The present study is focused on elucidating the relationship between CEVd infection and ethylene on disease development. To this purpose, the ethylene insensitive Never ripe (Nr) tomato mutants were infected with CEVd, and several aspects such as susceptibility to infection, defensive response, ethylene biosynthesis and ribosomal stress were studied. Phenotypic characterization revealed higher susceptibility to CEVd in these mutants, which correlated with higher expression levels of both defense and ethylene biosynthesis genes, as well as the ribosomal stress marker SlNAC082. In addition, Northern blotting revealed compromised ribosome biogenesis in all CEVd infected plants, particularly in Nr mutants. Our results indicate a higher ethylene biosynthesis in Nr mutants and suggest an important role of this phytohormone in disease development and ribosomal stress caused by viroid infection.

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Effect of Benzothiadiazole on the Metabolome of Tomato Plants Infected by Citrus Exocortis Viroid

Viruses ◽

10.3390/v11050437 ◽

2019 ◽

Vol 11 (5) ◽

pp. 437 ◽

Cited By ~ 3

Author(s):

María Pilar López-Gresa ◽

Celia Payá ◽

Ismael Rodrigo ◽

José María Bellés ◽

Susana Barceló ◽

...

Keyword(s):

Nuclear Magnetic Resonance ◽

Multivariate Data Analysis ◽

Viral Infections ◽

Aminobutyric Acid ◽

Resonance Spectroscopy ◽

Tomato Plants ◽

Metabolic Alterations ◽

Citrus Exocortis Viroid ◽

Viroid Infection ◽

Infected Tomato

Benzothiadiazole (BTH) is a functional analogue of the phytohormone salycilic acid (SA) involved in the plant immune response. NahG tomato plants are unable to accumulate SA, which makes them hypersusceptible to several pathogens. Treatments with BTH increase the resistance to bacterial, fungal, viroid, or viral infections. In this study, metabolic alterations in BTH-treated Money Maker and NahG tomato plants infected by citrus exocortis viroid (CEVd) were investigated by nuclear magnetic resonance spectroscopy. Using multivariate data analysis, we have identified defence metabolites induced after viroid infection and BTH-treatment. Glycosylated phenolic compounds include gentisic and ferulic acid accumulated in CEVd-infected tomato plants, as well as phenylalanine, tyrosine, aspartate, glutamate, and asparagine. Besides, an increase of γ-aminobutyric acid (GABA), glutamine, adenosine, and trigonelline, contributed to a clear discrimination between the metabolome of BTH-treated tomato leaves and their corresponding controls. Among them, GABA was the only metabolite significantly accumulated in both genotypes after the chemical treatment. In view of these results, the addition of GABA was performed on tomato plants infected by CEVd, and a reversion of the NahG hypersusceptibility to CEVd was observed, indicating that GABA could regulate the resistance to CEVd induced by BTH.

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