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Grapevine is one of the most economically important fruit crops cultivated worldwide. However, grapevine is highly susceptible to virus infections and exposed to the most diverse forms of viral diseases compared to other fruit crops, and virus-induced incompatibility affects plant growth to different degrees ranging from decline to death. The influence of virus-induced incompatibility could be mitigated to an acceptable level by using appropriate rootstocks. However, the viral tolerance of various grapevine rootstocks with diverse genetic backgrounds remains unclear, along with the identification of the specific viral tolerance factors. In this study, the viral tolerance of 21 grapevine rootstocks was evaluated in a green grafting system. Cabernet Franc varieties infected with a single virus [grapevine leafroll associated virus-1 (GLRaV-1)], a co-infection of two viruses (GLRaV-1 plus grapevine virus A—GVA), and no infection were used as the scions, respectively. The vegetative growth and photosynthetic function of the grafts were analyzed 4 months after grafting. The results indicated that some rootstocks could alleviate the influence of the virus infection, with vegetative growth and photosynthetic function sustained at a normal level, whereas other rootstocks were susceptible to the virus infection, resulting in a decline in the growth and photosynthetic function of the grafts. Our research provides evidence for the existence and diversity of viral tolerance among grapevine rootstocks, offering important information for appropriate rootstock selection in the establishment of new vineyards and in the breeding of grapevine rootstocks with enhanced viral tolerance.

Abstract Background Grapevine (Vitis vinifera L.), which has important nutritional values and health benefits, is one of the most economically important fruit crops cultivated worldwide. Several studies showed a large number of microRNAs (VvmiRNAs) involved in the modulation of grape growth and development, and many VvmiRNA families have multiple members. However, the way by which various members from the same miRNA family work is unclear, particularly in grapes. Results In this study, an important conserved VvmiR172 family (VvmiR172s) and their targets were set as a good example for elucidating the interaction degree, mechanism, and spatio-temporal traits of diverse members from the same miRNA family. miR-RACE and Stem-loop RT-PCR were used to identify the spatio-temporal expressions of various members of VvmiR172s; together with RLM-RACE, PPM-RACE, Western blot, transgenic technologies, their interaction degree, and regulation mechanism were further validated. The expression of VvmiR172c was significantly higher than that of VvmiR172a, b, and d and showed a positive correlation with the abundance of VvAP2 cleavage products. These findings indicated that VvmiR172c might be one of the main action factors of the VvmiR172 family in flower development. The ability of VvmiR172c to cleave target genes differed due to divergence in complementary degree with VvAP2 and expression levels of various members. In VvmiR172 transgenic lines, we observed that 35S::VvmiR172c resulted in the earliest and abundant flowering, indicating the strong function of VvmiR172c. In contrast, the non-significant phenotypic changes were detected in the VvAP2 transgenic lines. The qRT-PCR and Western bolt results demonstrated that VvmiR172c plays a major role in targeting VvAP2. Conclusions VvmiR172 up-regulated the expression of NtFT and decreased the expression of NtFLC. The up/down regulation of VvmiR172c was the most pronounced. The functions of four VvmiR172 members in grape differed, and miR172c had the strongest regulation on AP2.

Plant-specific YABBY (YAB) transcription factors play multiple roles in plant growth and development process. However, no comprehensive study has been performed in grapevines, especially to determine their roles in berry development and abiotic stress response. A total of seven VviYABs allocated to six chromosomal positions in grapevines were identified and classified into five subfamilies based on phylogenetic and structural analysis. Promoter element analysis and tissue-specific transcriptional response of VviYABs suggested that VviYABs might play vital roles in plant growth and development. VviYAB1, 2, 3, and 5 showed significantly higher expression levels in vegetative/green organs than in mature/woody tissues, implying that VviYABs might be involved in the regulatory switch from immature to mature developmental phases. The expression of VviYAB1, 2, 3, and VviFAS were gradually downregulated during berry developmental and ripening, which can be considered as putative molecular biomarkers between vegetative/green and mature/woody samples, and were used to identify key developmental and metabolic processes in grapevines. Furthermore, VviYAB1 expression was not markedly increased by gibberellic acid (GA3) treatment alone, but displayed significant upregulation when GA3 in combination with N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) were applied, suggesting an involvement of VviYAB1 in fruit expansion by mediating cytokinin signaling pathway. Additionally, microarray and RNA-seq data suggested that VviYABs showed transcriptional regulation in response to various abiotic and biotic stresses, including salt, drought, Bois Noir, Erysiphe necator, and GLRaV-3 infection. Overall, our results provide a better understanding of the classification and functions of VviYABs during berry development and in response to abiotic and biotic stresses in grapevines.

Abstract Background The plant-specific TCP transcription factors play different functions in multiple processes of plant growth and development. TCP family genes have been identified in several plant species, but no comprehensive analysis of the TCP family in grapevine has been undertaken to date, especially their roles in fruit development. Results A total of 18 non-redundant grapevine TCP (VvTCP) genes distributing on 11 chromosomes were identified. Phylogenetic and structural analysis showed that VvTCP genes were divided into two main classes - class I and class II. The Class II genes were further classified into two subclasses, the CIN subclass and the CYC/TB1 subclass. Segmental duplication was a predominant duplication event which caused the expansion of VvTCP genes. The cis-acting elements analysis and tissue-specific expression patterns of VvTCP genes demonstrated that these VvTCP genes might play important roles in plant growth and development. Expression patterns of VvTCP genes during fruit development and ripening were analyzed by RNA-Seq and qRT-PCR. Among them, 11 VvTCP genes were down-regulated during different fruit developmental stages, while only one VvTCP genes were up-regulated, suggesting that most VvTCP genes were probably related to early development in grapevine fruit. Futhermore, the expression of most VvTCP genes can be inhibited by drought and waterlogging stresses. Conclusions Our study establishes the first genome-wide analysis of the grapevine TCP gene family and provides valuable information for understanding the classification and functions of the TCP genes in grapevine.