The Early-Response to Dehydration six-like (ERD6l) is one of the largest families of sugar transporters in plants, however, is also one of the less studied with very few members characterized. In this work, we identified 18 members of the grapevine ERD6l family, analyzed their promoters and putative topology and additionally functionally characterized the member VvERD6l13. VvERD6l13 was strongly up-regulated in grape berries infected with Botrytis cinerea and Erysiphe necator in cv. Trincadeira and Carignan, respectively, suggesting an important role in grape berry-pathogen interaction, as we had hypothesized. In Cabernet Sauvignon Berry suspension cultured cells, VvERD6l13 was also up-regulated, by 4-fold, 48 h after elicitation with mycelium extract of B. cinerea. Besides being expressed in grape berries from various developmental stages, VvERD6l13 is also expressed in leaves, canes, flowers and, noticeably, in roots. Using tobacco and an hxt-null Saccharomyces cerevisiae strain as heterologous expression models, we showed that VvERD6l13 is localized at the plasma membrane and mediates the H+-dependent transport of sucrose (Km = 33 mM) thus confirming VvERD6l13 as a bona fide sugar transporter involved in sugar mobilization in grapevine and transcriptionally induced in response to biotic stress.
Keywords: Biotic stress; Grape berry; Grapevine; Sucrose; Sugar transporter; VvERD6l.
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