Characterizing the effects of nitrogen on grapevines with different scion/rootstock combinations: agronomic, metabolomic and transcriptomic approaches

Abstract

Most vineyards are grafted and include a variety (Vitis vinifera) grafted over a wild Vitis rootstock (hybrids of V. berlandieri, riparia and rupestris). Grape berry quality at harvest depends on a subtle balance between acidity and the concentrations of sugars, polyphenols and precursors of aroma compounds. The mechanisms controlling the balance of sugars/acids/polyphenols are influenced by the abiotic environment, in particular nitrogen supply, and interact with the genotypes of both the scion variety and the rootstock. Previous work suggests that some of the effects of water stress are in fact linked to a nitrogen deficiency driven indirectly by the reduction of water absorption. The root system (i.e rootstock) plays an important role in the uptake, reduction, transport and storage of nitrogen, and the water balance of the plant. In this context, we studied the mechanisms involved in the regulation of the synthesis of flavonoids in berries in response to nitrogen nutrition with different scion/rootstock combinations. Two varieties (Cabernet Sauvignon and Pinot Noir) were subjected to different nitrogen supplies in two experimental systems, in pots under semi-controlled conditions and in a vineyard. Agronomic analysis confirmed that high nitrogen supply increased the nitrogen content of different organs (leaf blades, petioles and berries) as well as leaf surface area and cane pruning weight. Metabolomic analyses of berry skins revealed an accumulation of secondary metabolites whose nature depended on the different rootstock/scion combinations studied. In addition, an increase in the synthesis of anthocyanins and flavonols was observed in the berry skins in response to the decrease in nitrogen nutrition. High nitrogen supply also increased the average degree of polymerization of tannins, while the contents of flavan-3-ols and procyanidins in the seeds and skins of the berries were not affected. Global transcriptome (using RNA sequencing) and targeted (qPCR) analyses showed changes in the abundance of transcripts of genes related to the metabolism of flavonoids in response to nitrogen status. Nitrogen supply also influenced the transcript amounts of positive (MYB) and negative (Lateral Boundary Organ Domain) transcription factors controlling of the biosynthesis of flavonoids.

Acknowledgements: This work was funded by the Conseil Interprofessionnel du Vin de Bordeaux, the KBBE Innovine project and COST Action FA 1106.