Unique features of the grapevine VvK5.1 channel support novel functions for outward K+ channels in plants.
Résumé
Grapevine (Vitisvinifera L.), one of the most important fruit crops, is a model plant for studying the physiology of fleshy fruits. Here, we report on the characterization of a new grapevine Shaker-type K+ channel, VvK5.1. Phylogenetic analysis revealed that VvK5.1 belongs to the SKOR-like subfamily. Our functional characterization of VvK5.1 in Xenopus oocytes confirms that it is an outwardly rectifying K+ channel that displays strict K+ selectivity. Gene expression level analyses by RT-qPCR showed that the VvK5.1 expression was detected in berries, roots, and flowers. In contrast to its Arabidopsis thaliana counterpart that is involved in K+ secretion in the root pericycle, allowing root-to-shoot K+ translocation, VvK5.1 expression territory is strongly enlarged. We showed by in situ hybridization that VvK5.1 is expressed in the phloem and perivascular cells of berries and in flower pistil. In the root, in addition to be expressed in the root pericycle like AtSKOR, a strong expression of VvK5.1 is detected in small cells facing the xylem that are involved in lateral root formation. This fine and selective expression pattern of VvK5.1 at early stage of lateral root primordia supports a suggested role for outward channel as switch on cell division initiation.
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