Grape quality for winemaking depends on sugar accumulation and metabolism in berries. Abscisic acid (ABA) and gibberellins (GAs) have been reported to control sugar allocation in economically important crops, although the mechanisms involved are still unknown. The present study tested if ABA and gibberellin A3 (GA3) enhance carbon allocation in fruits of grapevines by modifying phloem loading, phloem area and expression of sugar transporters in leaves and berries. Pot-grown Vitis vinifera cv. Malbec plants were sprayed with ABA and GA3 solutions. The amount of soluble sugars in leaves and berries related to photosynthesis were examined at three points of berry growth: pre-veraison, full veraison and post-veraison. Starch levels and amylase activity in leaves, gene expression of sugar transporters in leaves and berries and phloem anatomy were examined at full veraison. Accumulation of glucose and fructose in berries was hastened in ABA-treated plants at the stage of full veraison, which was correlated with enhancement of Vitis vinifera HEXOSE TRANSPORTER 2 (VvHT2) and Vitis vinifera HEXOSE TRANSPORTER 6 (VvHT6) gene expression, increases of phloem area and sucrose content in leaves. On the other hand, GA3 increased the quantity of photoassimilates delivered to the stem thus increasing xylem growth. In conclusion, stimulation of sugar transport by ABA and GA3 to berries and stems, respectively, was due to build-up of non-structural carbohydrates in leaves, modifications in phloem tissue and modulation in gene expression of sugar transporters.

Anthocyanin profiles are commonly used for grapevine cultivar identification because it is currently accepted that this trait is closely related to their genetic characteristics. Nevertheless, the extent of the variation for the anthocyanin profiles among clones of the same cultivar has not yet been studied in depth. The relative concentration of anthocyanins of 131 Malbec clones grown in the same vineyard was investigated by HPLC-DAD and the use of comprehensive statistic procedures. Complementarily, the expression level of structural and regulatory genes was studied via real time polymerase chain reaction. Significant variation was identified among the profiles of the clones, mainly due to variations in the amounts of malvidin derivatives. Finally, the differential expression in F3'5'H, OMT1 and AM2 genes seems to be related to the malvidin content variation. This work shows the existence of variation for the anthocyanin profiles among clones from the same grapevine cultivar and the putative involvement of genes related to hydroxylation, methylation, and transport of anthocyanins on the basis of such variation.

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Key message By studying three cv. Malbec clones cultivated in two vineyards with contrasting environmental conditions, we demonstrated that DNA methylation has an important role in the phenotypic plasticity and that epigenetic modulation is clone-dependent. Abstract Clonal selection and vegetative propagation determine low genetic variability in grapevine cultivars, although it is common to observe diverse phenotypes. Environmental signals may induce epigenetic changes altering gene expression and phenotype. The range of phenotypes that a genotype expresses in different environments is known as phenotypic plasticity. DNA methylation is the most studied epigenetic mechanism, but only few works evaluated this novel source of variability in grapevines. In the present study, we analyzed the effects on phenotypic traits and epigenome of three Vitis vinifera cv. Malbec clones cultivated in two contrasting vineyards of Mendoza, Argentina. Anonymous genome regions were analyzed using methylation-sensitive amplified polymorphism (MSAP) markers. Clone-dependent phenotypic and epigenetic variability between vineyards were found. The clone that presented the clearer MSAP differentiation between vineyards was selected and analyzed through reduced representation bisulfite sequencing. Twenty-nine differentially methylated regions between vineyards were identified and associated to genes and/or promoters. We discuss about a group of genes related to hormones homeostasis and sensing that could provide a hint of the epigenetic role in the determination of the different phenotypes observed between vineyards and conclude that DNA methylation has an important role in the phenotypic plasticity and that epigenetic modulation is clone-dependent.

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In purple carrots, anthocyanin pigmentation can be expressed in the entire root, or it can display tissue specific-patterns. Within the phloem, purple pigmentation can be found in the outer phloem (OP) (also called the cortex) and inner phloem (IP), or it can be confined exclusively to the OP. In this work, the genetic control underlying tissue-specific anthocyanin pigmentation in the carrot root OP and IP tissues was investigated by means of linkage mapping and transcriptome (RNA-seq) and phylogenetic analyses; followed by gene expression (RT-qPCR) evaluations in two genetic backgrounds, an F2 population (3242) and the inbred B7262. Genetic mapping of ‘root outer phloem anthocyanin pigmentation’ (ROPAP) and inner phloem pigmentation (RIPAP) revealed colocalization of ROPAP with the P1 and P3 genomic regions previously known to condition pigmentation in different genetic stocks, whereas RIPAP co-localized with P3 only. Transcriptome analysis of purple OP (POP) vs. non-purple IP (NPIP) tissues, along with linkage and phylogenetic data, allowed an initial identification of 28 candidate genes, 19 of which were further evaluated by RT-qPCR in independent root samples of 3242 and B7262, revealing 15 genes consistently upregulated in the POP in both genetic backgrounds, and two genes upregulated in the POP in specific backgrounds. These include seven transcription factors, seven anthocyanin structural genes, and two genes involved in cellular transport. Altogether, our results point at DcMYB7, DcMYB113, and a MADS-box (DCAR_010757) as the main candidate genes conditioning ROPAP in 3242, whereas DcMYB7 and MADS-box condition RIPAP in this background. In 7262, DcMYB113 conditions ROPAP.

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Vitivirus are ssRNA(+) viruses in the family Betaflexiviridae (subfamily Trivirinae). There are currently ten ICTV recognized virus species in the genus; nevertheless, the extended use of NGS technologies is rapidly expanding their diversity and six more have been proposed recently. Here, we present the characterization of a novel virus from grapevines, which fits the genomic architecture and evolutionary constraints to be classifiable within the Vitivirus genus. The detected virus sequence is 7,607 nt long, including a typical genome organization of ORFs encoding a replicase (RP), a 22 kDa protein, a movement protein, a coat protein (CP) and a nucleic acid binding protein. Here, we present the characterization of a novel virus from grapevines.Phylogenetic analyses based on the predicted RP and CP protein unequivocally places the new virus within the Vitivirus genus. Multiple independent RNAseq data confirmed the presence of the detected virus in berries at diverse developmental stages. Additionally, we detected, confirmed, and assembled virus sequences from grapevine samples of distinct cultivars from America, Europe, Asia and Oceania, sharing 74.9%-97.9% nt identity, suggesting that the identified virus is widely distributed and diverse. We propose the name grapevine virus L (GVL) to the detected Vitivirus.