An efficient method for transgenic callus induction from Vitis amurensis petiole

Vitis Myb14 confer cold and drought tolerance by activating lipid transfer protein genes expression and reactive oxygen species scavenge

The R2R3 Myb transcription factor exhibits a wide range of functions and participates in various biological processes in plant development, secondary metabolism, and abiotic stress tolerance, among others. Vitis Myb14 initially identified for its involvement in resveratrol synthesis in grapevines. In this study, we investigate its role in abiotic stress tolerance. Significant differences in expression were observed between two grape varieties, Vitis amurensis (Cold-hardy) and V. vinifera (Cold-sentitive), under abiotic and hormone treatments. Both VvMyb14 and VaMyb14 demonstrated responsiveness to cold, drought and high salt treatment, but VaMyb14 exhibited a quicker and more pronounced response. To investigate further, we overexpressed VaMyb14 in A. thalina and found that VaMyb14 OE plants showed significantly enhanced cold and drought tolerance compared to wild-type plants. Additionally, the transgenic lines exhibited increased antioxidant enzyme activity, particularly POD activity, and reduced MDA content. Microarray analysis of VaMyb14 OE plants revealed up-regulation of several ABA metabolism and signal transduction genes, including several LTPs, PP2Cs, RD29B, COR78 and other structural genes, indicating that VaMyb14 has the capacity to reprogram a significant signaling pathway. Furthermore, comparative mRNA sequencing profiling of 35S:VaMyb14 grapevine callus indicated its involvement its function involved in ROS scavenging and ABA signaling. These findings collectively demonstrate that Vitis Myb14 serves as a critical regulator in grapevine stress responses, contributing to improved defense against necrotrophic pathogens, enhanced phytoalexin resveratrol production, and increased drought or cold tolerance.

Decoding VaCOLD1 Function in Grapevines: A Membrane Protein Enhancing Cold Stress Tolerance

In globally cultivated grapevines, low-temperature stress poses a persistent challenge. Although COLD1 is recognized as a cold receptor in rice, its function in grapevine cold signaling is unclear. Here, we identified VaCOLD1, a transmembrane protein from the cold-tolerant Vitis amurensis Rupr, which is primarily located on plasma and endoplasmic reticulum membranes. Broadly expressed across multiple tissues, VaCOLD1 responds to various environmental stresses, particularly to cold. Its promoter contains distinct hormone- and stress-responsive elements, with GUS assays confirming widespread expression in Arabidopsis thaliana. Validation of interaction between VaCOLD1 and VaGPA1, together with their combined expression in yeast and grape calli, notably improved cold endurance. Overexpression of VaCOLD1 enhances cold tolerance in Arabidopsis by strengthening the CBF-COR signaling pathway. This is achieved through shielding against osmotic disturbances and modifying the expression of ABA-mediated genes. These findings emphasize the critical role of the VaCOLD1-VaGPA1 complex in mediating the response to cold stress via the CBF-COR pathway.

The roles of brassinosteroids and methyl jasmonate on postharvest grape by regulating the interaction between VvDWF4 and VvTIFY 5 A

Brassinosteroids (BRs) and methyl jasmonate (MeJA) are known for the regulation of plant development, and the crosstalk between them is important for plant growth. However, the interaction between them in the development of postharvest fruit is unresolved. We found that BR treatment enhanced the accumulation of sugar composition and aroma content, reduced the content of organic acids (such as tartaric acid) and promoted the coloring of grape callus. After the application of MeJA, the acidity increased and the sugar content decreased. The physiological data showed that exogenous BR also attenuated the JA inhibition of postharvest ripening in grape. DWF4 is a key enzyme in the BR biosynthetic pathway, and it can effectively regulate the content of endogenous BRs. TIFY 5 A, which belongs to the Jasmonate ZIM-domain (JAZ) family, can be baited by DWF4 through the Y2H experiment. TIFY 5 A represses the expression of dihydroflavonol-4-reductase (DFR) which plays a key role in the synthesis of anthocyanins, while this will be alleviated by VvDWF4. The interaction between TIFY 5 A and DWF4 contributes to the cross talk between JA and BR signalling pathways. This is also verified by the transgenic experimental results. The results in this paper provides a new insight into the relationship between BR and JA signalling pathways, which is important to the regulation of the postharvest ripening of grape.

Basic leucine zipper gene VvbZIP61 is expressed at a quantitative trait locus for high monoterpene content in grape berries

The widely appreciated muscat flavor of grapes and wine is mainly attributable to the monoterpenes that accumulate in ripe grape berries. To identify quantitative trait loci (QTL) for grape berry monoterpene content, an F1 mapping population was constructed by a cross between two grapevine genotypes, one with neutral aroma berries (cv. 'Beifeng') and the other with a pronounced muscat aroma (elite Vitis vinifera line '3-34'). A high-density genetic linkage map spanning 1563.7 cM was constructed using 3332 SNP markers that were assigned to 19 linkage groups. Monoterpenes were extracted from the berry of the F1 progeny, then identified and quantified by gas chromatography-mass spectrometry. Twelve stable QTLs associated with the amounts of 11 monoterpenes in berries were thus identified. In parallel, the levels of RNA in berries from 34 diverse cultivars were estimated by RNA sequencing and compared to the monoterpene content of the berries. The expression of five genes mapping to stable QTLs correlated well with the monoterpene content of berries. These genes, including the basic leucine zipper VvbZIP61 gene on chromosome 12, are therefore considered as potentially being involved in monoterpene metabolism. Overexpression of VvbZIP61 in Vitis amurensis callus through Agrobacterium-mediated transformation significantly increased the accumulation of several monoterpenes in the callus, including nerol, linalool, geranial, geraniol, β-myrcene, and D-limonene. It is hypothesized that VvbZIP61 expression acts to increase muscat flavor in grapes. These results advance our understanding of the genetic control of monoterpene biosynthesis in grapes and provide important information for the marker-assisted selection of aroma compounds in grape breeding.

Overexpression of grape ABA receptor gene VaPYL4 enhances tolerance to multiple abiotic stresses in Arabidopsis

BACKGROUND

Abscisic acid (ABA) plays a crucial role in abiotic stress responses. The pyrabactin resistance (PYR)/PYR-like (PYL)/regulatory component of ABA receptor (RCAR) proteins that have been characterized as ABA receptors function as the core components in ABA signaling pathway. However, the functions of grape PYL genes in response to different abiotic stresses, particularly cold stress, remain less studied.

RESULTS

In this study, we investigated the expression profiles of grape PYL genes upon cold treatment and isolated the VaPYL4 gene from Vitis amurensis, a cold-hardy grape species. Overexpression of VaPYL4 gene in grape calli and Arabidopsis resulted in enhanced cold tolerance. Moreover, plant resistance to drought and salt stress was also improved by overexpressing VaPYL4 in Arabidopsis. More importantly, we evaluated the contribution of VaPYL4 to plant growth and development after the treatment with cold, salt and drought stress simultaneously. The transgenic plants showed higher survival rates, earlier flowering phenotype, and heavier fresh weight of seedlings and siliques when compared with wild-type plants. Physiological analyses showed that transgenic plants had much lower content of malondialdehyde (MDA) and higher peroxidase (POD) activity. Stress-responsive genes such as RD29A (Responsive to desiccation 29A), COR15A (Cold responsive 15A) and KIN2 (Kinase 2) were also significantly up-regulated in VaPYL4-overexpressing Arabidopsis plants.

CONCLUSIONS

Our results show that overexpression of VaPYL4 could improve plant performance upon different abiotic stresses, which therefore provides a useful strategy for engineering future crops to deal with adverse environments.

GRAS-domain transcription factor PAT1 regulates jasmonic acid biosynthesis in grape cold stress response

Cultivated grapevine (Vitis) is a highly valued horticultural crop, and cold stress affects its growth and productivity. Wild Amur grape (Vitis amurensis) PAT1 (Phytochrome A signal transduction 1, VaPAT1) is induced by low temperature, and ectopic expression of VaPAT1 enhances cold tolerance in Arabidopsis (Arabidopsis thaliana). However, little is known about the molecular mechanism of VaPAT1 during the cold stress response in grapevine. Here, we confirmed the overexpression of VaPAT1 in transformed grape calli enhanced cold tolerance. Yeast two-hybrid and bimolecular fluorescence complementation assays highlighted an interaction between VaPAT1 with INDETERMINATE-DOMAIN 3 (VaIDD3). A role of VaIDD3 in cold tolerance was also indicated. Transcriptome analysis revealed VaPAT1 and VaIDD3 overexpression and cold treatment coordinately modulate the expression of stress-related genes including lipoxygenase 3 (LOX3), a gene encoding a key jasmonate biosynthesis enzyme. Co-expression network analysis indicated LOX3 might be a downstream target of VaPAT1. Both electrophoretic mobility shift and dual luciferase reporter assays showed the VaPAT1-IDD3 complex binds to the IDD-box (AGACAAA) in the VaLOX3 promoter to activate its expression. Overexpression of both VaPAT1 and VaIDD3 increased the transcription of VaLOX3 and JA levels in transgenic grape calli. Conversely, VaPAT1-SRDX (dominant repression) and CRISPR/Cas9-mediated mutagenesis of PAT1-ED causing the loss of the C-terminus in grape calli dramatically prohibited the accumulation of VaLOX3 and JA levels during cold treatment. Together, these findings point to a pivotal role of VaPAT1 in the cold stress response in grape by regulating JA biosynthesis.

Genome-wide identification of B-box proteins and VvBBX44 involved in light-induced anthocyanin biosynthesis in grape (Vitis vinifera L.)

Genome-wide identification, analysis and functional characterization of an unreported VvBBX gene showed a response to light and positive correlation with anthocyanin content, but also inhibition of light-induced anthocyanin synthesis. B-box (BBX) proteins are a class of zinc (Zn) finger transcription factors or regulators characterized by the presence of one or two BBX domains and play important roles in plant growth and development. However, the BBX genes' potential functions are insufficiently characterized in grape, a globally popular berry with high economic value. Here, 25 BBX family genes including a novel member (assigned VvBBX44) were identified genome widely in grape. The expression level of these VvBBXs were analyzed in 'Cabernet Sauvignon' (V. vinifera) stem, flower, leaf, tendril, petiole, and developing berries. The expression of VvBBX44 increased in developing 'Cabernet Sauvignon' berries. Its expression was inhibited in 'Jingxiu' and 'Muscat Hamburg' berry skin without sunlight. Furthermore, overexpression of VvBBX44 decreased the expression of LONG HYPOCOTYL 5 (VvHY5) and UDP-glucose flavonoid 3-O-glucosyltransferase (VvUFGT), and reduced the anthocyanin content in grape calli. Our results suggest that VvBBX44 may play an important role in grape berry coloring by directly repressing VvHY5 expression. This study provides new insights into the potential role of VvBBXs in berry development and light response and contributes to the understanding on the regulation mechanism of VvBBX44 in anthocyanin biosynthesis.

Perilla frutescens Extracts Enhance DNA Repair Response in UVB Damaged HaCaT Cells

Physiological processes in skin are associated with exposure to UV light and are essential for skin maintenance and regeneration. Here, we investigated whether the leaf and callus extracts of Perilla frutescens (Perilla), a well-known Asian herb, affect DNA damage response and repair in skin and keratinocytes exposed to Untraviolet B (UVB) light. First, we examined the protective effects of Perilla leaf extracts in UVB damaged mouse skin in vivo. Second, we cultured calluses using plant tissue culture technology, from Perilla leaf explant and then examined the effects of the leaf and callus extracts of Perilla on UVB exposed keratinocytes. HaCaT cells treated with leaf and callus Perilla extracts exhibited antioxidant activities, smaller DNA fragment tails, and enhanced colony formation after UVB exposure. Interestingly, keratinocytes treated with the leaf and callus extracts of Perilla showed G1/S cell cycle arrest, reduced protein levels of cyclin D1, Cyclin Dependent Kinase 6 (CDK6), and γH₂AX, and enhanced levels of phosphorylated checkpoint kinase 1 (pCHK1) following UVB exposure. These observations suggest that the leaf and callus extracts of Perilla are candidate nutraceuticals for the prevention of keratinocyte aging.

Transcriptomic analysis of grapevine Dof transcription factor gene family in response to cold stress and functional analyses of the VaDof17d gene

Dof genes enhance cold tolerance in grapevine and VaDof17d is tightly associated with the cold-responsive pathway and with the raffinose family oligosaccharides. DNA-binding with one finger (Dof) proteins comprise a large family that plays important roles in the regulation of abiotic stresses. No in-depth analysis of Dof genes has been performed in the grapevine. In this study, we analyzed a total of 25 putative Dof genes in grapevine at genomic and transcriptomic levels, compiled expression profiles of 11 selected VaDof genes under cold stress and studied the potential function of the VaDof17d gene in grapevine calli. The 25 Dof proteins can be classified into four phylogenetic groups. RNA-seq and qRT-PCR results demonstrated that a total of 11 VaDof genes responded to cold stress. Comparative mRNA sequencing of 35S::VaDof17d grape calli showed that VaDof17d was tightly associated with the cold-responsive pathway and with the raffinose family oligosaccharides (RFOs), as observed by the up-regulation of galactinol synthase (GolS) and raffinose synthase genes. We found that the Dof17d-ED (CRISPR/Cas9-mediated mutagenesis of Dof17d-ED) mutant had low cold tolerance with a decreased RFOs level during cold stress. These results formed the fundamental knowledge for further analysis of the biological roles of Dof genes in the grapevine's adaption to cold stresses.

Somatic embryogenesis is an effective strategy for dissecting chimerism phenomena in Vitis vinifera cv Nebbiolo

The tendency of somatic embryogenesis to regenerate plants only from the L1 layer, associated with the spread of chimerism in grapevine, must be carefully considered in the framework of biotechnological improvement programmes. Grapevine is an important fruit crop with a high economic value linked to traditional genotypes that have been multiplied for centuries by vegetative propagation. In this way, somatic variations that can spontaneously occur within the shoot apical meristem are fixed in the whole plant and represent a source of intra-varietal variability. Previously identified inconsistencies in the allelic calls of single nucleotide variants (SNVs) suggested that the Vitis vinifera 'Nebbiolo' CVT185 clone is a potential periclinal chimera. We adopted the somatic embryogenesis technique to separate the two genotypes putatively associated with the L1 and L2 layers of CVT185 into different somaclones. Despite the recalcitrance of 'Nebbiolo' to the embryogenic process, 58 somaclones were regenerated and SNV genotyping assays attested that the genotype of all them differed from that of the mother plant and was only attributable to L1. The results confirmed that L2 has low or no competence for differentiating somatic embryos. After one year in the greenhouse, the somaclones showed no phenotypic alterations in comparison with the mother plant; however further analyses are needed to identify potential endogenous sources of variation. The tendency of somatic embryogenesis to regenerate plants only from L1 must be carefully considered in the framework of biotechnological improvement programmes in this species.

Embryogenic callus induction and Agrobacterium-mediated genetic transformation of 'Shine Muscat' grape

We established a method for embryogenic callus induction and highly efficient Agrobacterium-mediated genetic transformation of a table grape cultivar 'Shine Muscat' (Vitis labruscana). Embryogenic calli were induced using flower bud filaments from a dormant cane. Agrobacterium strain LBA4404 harboring the binary plasmid pBin19-sgfp, which contains the sgfp and nptII genes, was used to infect embryogenic calli. Infected calli were selected on 1/2 MS medium containing 5% maltose and 2% agar supplemented with 15 mg l^-1 kanamycin. Efficiency of transformation of regenerated plants reached nearly 100% as determined by PCR and Southern blot analyses. The developed method will open a new avenue for genome editing of 'Shine Muscat' and contribute to the advancement of grape breeding.

Transcriptomic Analysis of the Grapevine LEA Gene Family in Response to Osmotic and Cold Stress Reveals a Key Role for VamDHN3

Late embryogenesis abundant (LEA) proteins comprise a large family that plays important roles in the regulation of abiotic stress, however, no in-depth analysis of LEA genes has been performed in grapevine to date. In this study, we analyzed a total of 52 putative LEA genes in grapevine at the genomic and transcriptomic level, compiled expression profiles of four selected (V. amurensis) VamLEA genes under cold and osmotic stresses, and studied the potential function of the V. amurensis DEHYDRIN3 (VamDHN3) gene in grapevine callus. The 52 LEA proteins were classified into seven phylogenetic groups. RNA-seq and quantitative real-time PCR results demonstrated that a total of 16 and 23 VamLEA genes were upregulated under cold and osmotic stresses, respectively. In addition, overexpression of VamDHN3 enhanced the stability of the cell membrane in grapevine callus, suggesting that VamDHN3 is involved in osmotic regulation. These results provide fundamental knowledge for the further analysis of the biological roles of grapevine LEA genes in adaption to abiotic stress.

Recent advances in biotechnological studies on wild grapevines as valuable resistance sources for smart viticulture

Cultivated grapevines, Vitis vinifera subsp. sativa, are thought to have been domesticated from wild populations of Vitis vinifera subsp. sylvestris in Central Asia. V. vinifera subsp. sativa is one of the most economically important fruit crops worldwide. Since cultivated grapevines are susceptible to multiple biotic and abiotic soil factors, they also need to be grafted on resistant rootstocks that are mostly developed though hybridization between American wild grapevine species (V. berlandieri, V. riparia, and V. rupestris). Therefore, wild grapevine species are essential genetic materials for viticulture to face biotic and abiotic stresses in both cultivar and rootstock parts. Actually, viticulture faces several environmental constraints that are further intensified by climate change. Recently, several reports on biotic and abiotic stresses-response in wild grapevines revealed accessions tolerant to different constraints. The emergence of advanced techniques such as omics technologies, marker-assisted selection (MAS), and functional analysis tools allowed a more detailed characterization of resistance mechanisms in these wild grapevines and suggest a number of species (V. rotundifolia, V. rupestris, V. riparia, V. berlandieri and V. amurensis) have untapped potential for new resistance traits including disease resistance loci and key tolerance genes. The present review reports on the importance of different biotechnological tools in exploring and examining wild grapevines tolerance mechanisms that can be employed to promote elite cultivated grapevines under climate change conditions.

The ethylene response factor VaERF092 from Amur grape regulates the transcription factor VaWRKY33, improving cold tolerance

Cold stress is a major limiting factor in grape (Vitis) productivity. In this study, we characterized a cold-responsive ethylene response factor (ERF) transcription factor, VaERF092, from Amur grape (Vitis amurensis). VaERF092 expression was induced by both low temperatures and the ethylene precursor 1-aminocyclopropane-1-carboxylate (ACC), but was suppressed by treatment with the ethylene inhibitor aminoethoxyvinylglycine (AVG) under cold conditions. Ectopic expression of VaERF092 in Arabidopsis thaliana enhanced cold tolerance. Co-expression network analysis of V. vinifera genes indicated that WRKY33 might be a downstream target of VaERF092. This hypothesis was supported by the fact that VaWRKY33 was expressed temporally after VaERF092 expression and could also be induced by cold and ACC, and inhibited by AVG. Yeast one-hybrid, transient β-glucuronidase (GUS) and dual-luciferase reporter assays provided evidence for an interaction between VaERF092 and a GCC-box element in the VaWRKY33 promoter. In addition, heterologous overexpression of VaWRKY33 in A. thaliana resulted in enhanced cold tolerance. VaERF092- and VaWRKY33 overexpressing grape calli showed lower low-temperature exothermic values than the empty vector (EV) calli, indicating enhanced tolerance to cold. Together, these results indicated that VaERF092 regulates VaWRKY33 through binding to its promoter GCC-box, leading to enhanced cold stress tolerance.

Factors Affecting the Regeneration, via Organogenesis, and the Selection of Transgenic Calli in the Peach Rootstock Hansen 536 (Prunus persica × Prunus amygdalus) to Express an RNAi Construct against PPV Virus

Prunus spp. is one of the most recalcitrant fruit tree species in terms of in vitro regeneration and transformation, mostly when mature tissues are used as explants. The present study describes the in vitro regeneration via indirect organogenesis, and Agrobacterium tumefaciens-mediated transformation of the peach rootstock Hansen 536 (Prunus persica × Prunus amygdalus) through the use of meristematic bulks (MBs) as starting explants. Efficient adventitious shoot regeneration was obtained when Hansen 536 MBs were cultured on an optimized medium consisting of modified McCown Woody Plant medium (WPM) enriched with 4.4 M 6-Benzyladenine (BA), 0.1 M 1-Naphthaleneacetic acid (NAA) and 6.0 g L-1 plant agar S1000 (B&V). MB slices were used later as starting explants for Agrobacterium-mediated transformation to introduce an RNAi construct "ihp35S-PPV194" against PPV virus. Transgenic events were identified by both green fluorescent protein (GFP) screening and kanamycin selection at different concentrations (0, 17 or 42 M). GFP-fluorescent proliferating callus lines were selected and confirmed to stably express the ihp35S-PPV194::eGFP gene construct by molecular analysis. Although shoot regeneration from these transgenic calli has not been obtained yet, this represents one of the few examples of successful attempts in peach genetic transformation from somatic tissues, and also serves as a useful in vitro system for future gene functional analysis in peach.

VvSWEET10 Mediates Sugar Accumulation in Grapes

Sugar accumulation is a critical event during grape berry ripening that determines the grape market values. Berry cells are highly dependent on sugar transporters to mediate cross-membrane transport. However, the role of sugar transporters in improving sugar accumulation in berries is not well established in grapes. Herein we report that a Sugars Will Eventually be Exported Transporter (SWEET), that is, VvSWEET10, was strongly expressed at the onset of ripening (véraison) and can improve grape sugar content. VvSWEET10 encodes a plasma membrane-localized transporter, and the heterologous expression of VvSWEET10 indicates that VvSWEET10 is a hexose-affinity transporter and has a broad spectrum of sugar transport functions. VvSWEET10 overexpression in grapevine calli and tomatoes increased the glucose, fructose, and total sugar levels significantly. The RNA sequencing results of grapevine transgenic calli showed that many sugar transporter genes and invertase genes were upregulated and suggest that VvSWEET10 may mediate sugar accumulation. These findings elucidated the role of VvSWEET10 in sugar accumulation and will be beneficial for the improvement of grape berry quality in the future.

The GARP/MYB-related grape transcription factor AQUILO improves cold tolerance and promotes the accumulation of raffinose family oligosaccharides

Grapevine (Vitis vinifera L.) is a widely cultivated fruit crop whose growth and productivity are greatly affected by low temperatures. On the other hand, wild Vitis species represent valuable genetic resources of natural stress tolerance. We have isolated and characterized a MYB-like gene encoding a putative GARP-type transcription factor from Amur grape (V. amurensis) designated as VaAQUILO. AQUILO (AQ) is induced by cold in both V. amurensis and V. vinifera, and its overexpression results in significantly improved tolerance to cold both in transgenic Arabidopsis and in Amur grape calli. In Arabidopsis, the ectopic expression of VaAQ increased antioxidant enzyme activities and up-regulated reactive oxygen species- (ROS) scavenging-related genes. Comparative mRNA sequencing profiling of 35S:VaAQ Arabidopsis plants suggests that this transcription factor is related to phosphate homeostasis like their Arabidopsis closest homologues: AtHRS1 and AtHHO2. However, when a cold stress is imposed, AQ is tightly associated with the cold-responsive pathway and with the raffinose family oligosaccharides (RFOs), as observed by the up-regulation of galactinol synthase (GoLS) and raffinose synthase genes. Gene co-expression network (GCN) and cis-regulatory element (CRE) analyses in grapevine indicated AQ as potentially regulating VvGoLS genes. Increased RFO content was confirmed in both transgenic Arabidopsis and Amur grape calli overexpressing VaAQ. Taken together, our results imply that AQ improves cold tolerance through promoting the accumulation of osmoprotectants.