Abstract
BackgroundZinc (Zn) deficiency is one of the most widespread mineral nutritional problems that affect normal development in plants. Because Zn cannot passively diffuse across cell membranes, it must be transported into intracellular compartments for all biological processes where Zn is required. Several members of the Zinc-regulated transporters, Iron-regulated transporter-like Protein (ZIP) gene family have been characterized in plants, and have shown to be involved in metal uptake and transport. This study describes the first putative Zn transporter in grapevine. Unravelling its function may explain an important symptom of Zn deficiency in grapevines, which is the production of clusters with fewer and usually smaller berries than normal.ResultsWe identified and characterized a putative Zn transporter from berries of Vitis vinifera L., named VvZIP3. Compared to other members of the ZIP family identified in the Vitis vinifera L. genome, VvZIP3 is mainly expressed in reproductive tissue - specifically in developing flowers - which correlates with the high Zn accumulation in these organs. Contrary to this, the low expression of VvZIP3 in parthenocarpic berries shows a relationship with the lower Zn accumulation in this tissue than in normal seeded berries where its expression is induced by Zn. The predicted protein sequence indicates strong similarity with several members of the ZIP family from Arabidopsis thaliana and other species. Moreover, VvZIP3 complemented the growth defect of a yeast Zn-uptake mutant, ZHY3, and is localized in the plasma membrane of plant cells, suggesting that VvZIP3 has the function of a Zn uptake transporter.ConclusionsOur results suggest that VvZIP3 encodes a putative plasma membrane Zn transporter protein member of the ZIP gene family that might play a role in Zn uptake and distribution during the early reproductive development in Vitis vinifera L., indicating that the availability of this micronutrient may be relevant for reproductive development.
Highlights
Zinc (Zn) deficiency is one of the most widespread mineral nutritional problems that affect normal development in plants
Expression analysis revealed that VvZIP3 was transcribed principally in reproductive tissues - in developing flowers, organs that present the highest accumulation of Zn. These results suggest that VvZIP3 participates in Zn uptake during flower development contributing to the normal development in Vitis vinifera L
Sequence analysis and comparison of the cDNA with genomic DNA shows that VvZIP3 is composed of three exons and two introns, being a single copy gene located in chromosome I of grapevine
Summary
Zinc (Zn) deficiency is one of the most widespread mineral nutritional problems that affect normal development in plants. It has been demonstrated that Zn deficiency is one of the most widespread mineral nutritional problems affecting normal development in plants [5,6,7,8] This includes altered expression and/or function of proteins at the metabolic level that leads to different physiological symptoms characterized by root apex necrosis. It has been suggested that this reduction in shoot growth results from the fact that Zn is essential for the synthesis of tryptophan, a precursor of the phytohormone indoleacetic acid (IAA) [10] Another important symptom of Zn deficiency in grapevines is the production of clusters with few berries that vary in size from normal to very small [10,11,12]. Under conditions of Zn deficiency, application of foliar Zn fertilizer shortly before anthesis increases the number of flowers that set fruit [10,11,12,13,14]
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