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Ascorbic acid regulation in leaves and fruits of tomato ecotypes infected by Eggplant Mottled Dwarf Virus

Zarrillo, A., Minutolo, M., Alioto, D., Errico, A.
Scientia horticulturae 2017 v.225 pp. 512-524
Eggplant mottled dwarf virus, Solanum lycopersicum, ascorbic acid, biochemical pathways, ecotypes, fruits, galactose, gene expression, gene expression regulation, genes, leaves, oxidative stress, plant diseases and disorders, plant viruses, recycling, ripening, tomatoes
Changes in ascorbic acid levels and gene expression of its biosynthetic pathway were studied in Solanum lycopersicum plants inoculated with Eggplant Mottled Dwarf Virus (EMDV). Data showed that EMDV inoculation caused a significant decrease of tAsA in the leaves of two ecotypes at 7 dpi, before symptom appearance, and at 21 dpi when symptoms were most evident and was restored at 35 dpi when symptoms remained constant. Biosynthetic gene expression decreased at 7 and 21 dpi. In Tondo Giallo the tAsA levels were restored at 35 dpi; which coincided with an upregulation of almost all genes. In immature fruits of Maiese, the decrease of tAsA was accompanied by a substantial down-regulation of genes in L-galactose and/or L-galactonic acid pathways while in Tondo Giallo the constant level of tAsA was associated with an increase of ASA and with an upregulation of gene expression. This could be a direct consequence of a high ascorbate turnover and a low level of oxidative stress. In ripe fruits, the higher tAsA content observed in Maiese was associated with a general upregulation of gene expression, while in Tondo Giallo it could depend on a high rate of ascorbate recycling as suggested by the upregulation of the gene MDHAR2. Collectively these results provide evidence that the interaction between Solanum lycopersicon and EMDV affects ascorbic acid quality and accumulation in relation to tomato ecotype, plant developmental stage, and fruit ripening stage.