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Drought stress impedes viticultural plant growth and development by modifying various metabolic pathways. However, the regulatory network response underlying drought stress is not yet clear. In this study, the leaves and roots of "Shine Muscat" ("SM," Vitis labruscana × Vitis vinifera) and "Thompson Seedless" ("TS," V. vinifera L. cv.) were subjected to drought stress to study the regulatory network used by drought stress. Morphophysiological results showed that the malondialdehyde content after 28 days of drought stress increased more significantly in "TS" than "SM." Furthermore, the multiomics analysis studies showed that a total of 3036–6714 differentially expressed genes and 379–385 differentially abundant metabolites were identified in "SM" and "TS" grapevine cultivars under drought stress. Furthermore, the retained intron was the major form of differential alternative splicing event under drought stress. The photosynthesis pathway, antioxidant system, plant hormone signal transduction, and osmotic adjustment were the primary response systems in the two grapevine cultivars under drought stress. We have identified GRIK1, RFS2, and LKR/SDH as the hub genes in the coexpression network of drought stress. In addition, the difference in the accumulation of pheophorbide‐a reveals different drought resistance mechanisms in the two grapevine cultivars. Our study explained the difference in drought response between cultivars and tissues and identified drought stress‐responsive genes, which provides reference data for further understanding the regulatory network of drought tolerance in grapevine. [ABSTRACT FROM AUTHOR]

Grapevine downy mildew is the most serious disease of grapevine cultivars that affects the rate of resistance/susceptibility to Plasmopara viticola. In this study, we used the susceptible cultivar "Zitian Seedless" and the resistant cultivar "Kober 5BB" as materials to determine the transcriptome differences and phenotypes of the leaves after inoculation with downy mildew. The differences in microstructures and molecular levels were compared and analyzed. Fluorescence staining and microscopic observations confirmed that hypersensitive cell death occurred around the stomata in "Kober 5BB" infected by downy mildew zoospores. Meanwhile, transcriptomic profiling indicated that there were 11,713 and 6,997 gene expression differences between the resistant and susceptible cultivars at 72 h after inoculation when compared to control (0 h), respectively. The differentially expressed genes of the two cultivars are significantly enriched in different pathways, including response to plant-pathogen interaction, mitogen-activated protein kinase (MAPK) signaling pathway, plant hormone signal transduction, phenylpropanoid, and flavonoid biosynthesis. Furthermore, the results of functional enrichment analysis showed that H2O2 metabolism, cell death, reactive oxygen response, and carbohydrate metabolism are also involved in the defense response of "Kober 5BB," wherein a total of 322 key genes have been identified. The protein interaction network showed that metacaspases (MCAs), vacuolar processing enzymes (VPEs), and Papain-like cysteine proteases (PLCPs) play an important role in the execution of hypersensitive responses (HR). In conclusion, we demonstrated that HR cell death is the key strategy in the process of grape defense against downy mildew, which may be mediated or activated by Caspase-like proteases. [ABSTRACT FROM AUTHOR]

Background: Papain-like cysteine proteases (PLCPs), a large group of cysteine proteases, are structurally related to papain. The members belonging to PLCPs family contribute to plant immunity, senescence, and defense responses in plants. The PLCP gene family has been identified in Arabidopsis, rice, soybean, and cotton. However, no systematic analysis of PLCP genes has been undertaken in grapevine. Since Plasmopara viticola as a destructive pathogen could affect immunity of grapes in the field, we considered that the members belonged to PLCPs family could play a crucial role in defensive mechanisms or programmed cell death. We aimed to evaluate the role of PLCPs in 2 different varieties of grapevines and compared the changes of their expressions with the transcriptional data in response to P. viticola. Results: In this study, 23 grapevine PLCP (VvPLCP) genes were identified by comprehensive bioinformatics analysis. Subsequently, the chromosomal localizations, gene structure, conserved domains, phylogenetic relationship, gene duplication, and cis-acting elements were analyzed. Numerous cis-acting elements related to plant development, hormone, and stress responses were identified in the promoter of the VvPLCP genes. Phylogenetic analysis grouped the VvPLCP genes into nine subgroups. The transcription of VvPLCP in different inoculation time points and varieties indicated that VvPLCP may have vital functions in grapevine defense against Plasmopara viticola. According to transcriptome data and qPCR analysis, we observed the increasing expression levels of VvRD21–1 at 72 h after inoculation in resistant variety, inferring that it was related to grape downy mildew resistance. Meanwhile, 3 genes including VvXBCP1, VvSAG12–1, and VvALP1 showed higher expression at 24 h after pathogen inoculation in the susceptible variety and might be related to the downy mildew phenotype. We nominated these four genes to function during hypersensitive response (HR) process, inferring that these genes could be associated with downy mildew resistance in grapes. Conclusions: Our results provide the reference for functional studies of PLCP gene family, and highlight its functions in grapevine defense against P. viticola. The results help us to better understand the complexity of the PLCP gene family in plant immunity and provide valuable information for future functional characterization of specific genes in grapevine. [ABSTRACT FROM AUTHOR]

Summary: In grape, MYBA1 and MYBA2 at the colour locus are the major genetic determinants of grape skin colour, and the mutation of two functional genes (VvMYBA1 and VvMYBA2) from these loci leads to white skin colour. This study aimed to elucidate the regulation of grape berry coloration by isolating and characterizing VvMYBA2w and VvMYBA2r alleles. The overexpression of VvMYBA2r up‐regulated the expression of anthocyanin biosynthetic genes and resulted in higher anthocyanin accumulation in transgenic tobacco than wild‐type (WT) plants, especially in flowers. However, the ectopic expression of VvMYBA2w inactivated the expression of anthocyanin biosynthetic genes and could not cause obvious phenotypic modulation in transgenic tobacco. Unlike in VvMYBA2r, CA dinucleotide deletion shortened the C‐terminal transactivation region and disrupted the transcriptional activation activity of VvMYBA2w. The results indicated that VvMYBA2r positively regulated anthocyanin biosynthesis by forming the VvMYBA2r‐VvMYCA1‐VvWDR1 complex, and VvWDR1 enhanced anthocyanin accumulation by interacting with the VvMYBA2r‐VvMYCA1 complex; however, R44L substitution abolished the interaction of VvMYBA2w with VvMYCA1. Meanwhile, both R44L substitution and CA dinucleotide deletion seriously affected the efficacy of VvMYBA2w to regulate anthocyanin biosynthesis, and the two non‐synonymous mutations were additive in their effects. Investigation of the colour density and MYB haplotypes of 213 grape germplasms revealed that dark‐skinned varieties tended to contain HapC‐N and HapE2, whereas red‐skinned varieties contained high frequencies of HapB and HapC‐Rs. Regarding ploidy, the higher the number of functional alleles present in a variety, the darker was the skin colour. In summary, this study provides insight into the roles of VvMYBA2r and VvMYBA2w alleles and lays the foundation for the molecular breeding of grape varieties with different skin colour. [ABSTRACT FROM AUTHOR]

B Correction to: BMC Plant Biol 21, 499 (2021) b B https://doi.org/10.1186/s12870-021-03279-w b Following publication of the original article [[1]], Peijie Gong is the co-1st author and one of the corresponding authors of this article. Jun Kang and Peijie Gong contributed equally to this work. [Extracted from the article]

Copper stress is one of the most severe heavy metal stresses in plants. Grapevine has a relatively higher copper tolerance than other fruit crops. However, there are no reports regarding the tolerance mechanisms of the 'Shine Muscat' ('SM') grape to a low degree of excess copper stress (Low-ECS). Based on the physiological indicators and multi-omics (transcriptome, proteome, metabolome, and microRNAome) data, 8 h (h) after copper treatment was the most severe stress time point. Nonetheless, copper stress was alleviated 64 h after treatment. Cu ion transportation, photosynthesis pathway, antioxidant system, hormone metabolism, and autophagy were the primary response systems in 'SM' grapevine under Low-ECS. Numerous genes and proteins, such as HMA5 , ABC transporters, PMM , GME , DHAR , MDHAR , ARGs , and ARPs, played essential roles in the 'SM' grapevine's response to Low-ECS. This work was carried out to gain insights into the multi-omics responses of 'SM' grapevine to Low-ECS. This study provides genetic and agronomic information that will guide better vinery management and breeding copper-resistant grape cultivars. [Display omitted] • Response network of grapevine leaves to Low-ECS were constructed via multi-omics. • Chelation, segregation and efflux of copper were enhanced in leaves under Low-ECS. • Antioxidant systems and hormone metabolism were induced to alleviate copper stress. • Low-ECS enhanced ARGs and ARPs expressions and autophagosome formation. The joint analysis of multi omics and physiological indexes indicated that grapevines mainly responded to Low-ECS by regulating copper transport, antioxidant pathway, hormone metabolism, and autophagy. [ABSTRACT FROM AUTHOR]

Background: Bud dormancy is a strategic mechanism plants developed as an adaptation to unfavorable environments. The grapevine (Vitis vinifera) is one of the most ancient fruit vine species and vines are planted all over the world due to their great economic benefits. To better understand the molecular mechanisms underlying bud dormancy between adjacent months, the transcriptomes of 'Rosario Bianco' grape buds of 6 months and three nodes were analyzed using RNA-sequencing technology and pair-wise comparison. From November to April of the following year, pairwise comparisons were conducted between adjacent months. Results: A total of 11,647 differentially expressed genes (DEGs) were obtained from five comparisons. According to the results of cluster analysis of the DEG profiles and the climatic status of the sampling period, the 6 months were divided into three key processes (November to January, January to March, and March to April). Pair-wise comparisons of DEG profiles of adjacent months and three main dormancy processes showed that the whole grapevine bud dormancy period was mainly regulated by the antioxidant system, secondary metabolism, cell cycle and division, cell wall metabolism, and carbohydrates metabolism. Additionally, several DEGs, such as VvGA2OX6 and VvSS3, showed temporally and spatially differential expression patterns, which normalized to a similar trend during or before April. Conclusion: Considering these results, the molecular mechanisms underlying bud dormancy in the grapevine can be hypothesized, which lays the foundation for further research. [ABSTRACT FROM AUTHOR]

The inappropriate application of copper (Cu)-based fungicides causes toxicity in the vineyard. However, limited data are available about which are the tolerant grapes cultivars and underlying physiological and molecular mechanisms against Cu stress. Therefore, we evaluated the damage status of 302 perennial Vitis germplasm resources by spraying their leaves with a 10 mM Cu (excessive Cu) solution for 48 h. Then, we studied the effects of Cu-induced toxicity in two Vitis vinifera × Vitis labruscana (V. vinifera × V. labruscana) cultivars, i.e., 'Takasumi' ('Ta') and 'Moldova'('Mo') with significantly different Cu tolerance levels by analyzing their gene expression, metabolites, and other physiological parameters. V. vinifera × V. labruscana showed a higher Cu tolerance than Vitis vinifera (V. vinifera), with 'Ta' being more tolerant than 'Mo'. Herein, we detected 2,083 up-regulated and 4,474 down-regulated differentially expressed genes (DEGs), and 87 up-regulated and 84 down-regulated differentially accumulated metabolites (DAMs) in Ta vs. Mo. As compared to the Cu-sensitive cultivars, the Cu-tolerant cultivars displayed some Cu and reactive oxygen species (ROS) detoxification measures, including (a) inhibiting Cu uptake and enhancing its transportation, sequestration, and efflux; (b) ROS scavenging by upregulating antioxidant-related genes, like CAT8 , SOD1 , and TRX2 , and increasing the accumulation of ascorbate-glutathione (AsA-GSH) cycle metabolites (ascorbic acid and oxidized L -glutathione); (c) inducing autophagy-related genes expression and secondary metabolism due to elevated intermediary metabolites, including those of tricarboxylic acid (TCA) cycle (DL-malic acid, citric acid, and fumaric acid) and flavonoid pathway (catechin, procyanidin B1, and theaflavin); (d) increasing the content of phytohormones, like abscisic acid (ABA), brassinosteroids (BRs), and salicylic acid (SA). Therefore, our findings will not only support future functional analysis but also decipher the possible Cu-induced stress response mechanisms underlying the cultivar-level differences in Cu accumulation. [Display omitted] • V. vinifera × V. labruscana showed higher Cu tolerance levels than V. vinifera. • Inhibiting Cu uptake and enhancing Cu transportation might improve tolerance of Vitis. • Activating antioxidative mechanisms might enhance Cu tolerance of Vitis. [ABSTRACT FROM AUTHOR]

• The difference in the content and composition of anthocyanins in three grape cultivars was investigated. • Transcriptome sequencing analyzes the changes in gene expression levels during the development of different color grape cultivars. • WGCNA reveals modules of co-expressed genes related to anthocyanins and identified hub genes related to anthocyanin synthesis. Anthocyanins as plant pigments are responsible for the color of the grape berry. The major concern among consumers is color, quality, and appearance, therefore, skin color is the most important item that affects consumer purchases. In this study, we used three grape cultivars namely Red globe (bright red), Kyoho (purple-red), and Wink (purple-black), and evaluated color changes in three different developmental stages according to time course including 15 days after the berry color shift from green to red (V1), 25 days after the berry color shift from green to red (V2), and 35 days after the berry color shift from green to red (V3). The dynamic changes in anthocyanin content and components were detected using "High-Performance Liquid Chromatography mass spectrometry/mass spectrometry (HPLC-MS/MS)" technology. Furthermore, we performed transcriptome sequencing and identified the genes involved in the anthocyanin biosynthesis and accumulation in grape berry development. In total, we detected 13 different anthocyanin components in three grape cultivars. Malvidin, petunidin, and delphinidin derivates are the main components of dark colored grape (Kyoho and Wink), while cyanidin and pelargonidin derivates are the sources of bright-colored grape (Red globe). According to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, many DEGs were enrichment in phenylpropanoid biosynthesis and flavonoid biosynthesis. We also found thirty-nine DEGs to be involved in the anthocyanin metabolism and accumulation. Furthermore, using weighted gene correlation analysis (WGCNA), three modules (blue, magenta, and tan) and nineteen hub genes were highly correlated with anthocyanin variation. Our research provided new insights for elucidating the anthocyanin metabolic pathway and related genes, signal perception and transduction during grape berries development at different stages. [ABSTRACT FROM AUTHOR]