A Tunisian wild grape leads to metabolic fingerprints of salt tolerance

Deciphering the regulatory networks involved in mild and severe salt stress responses in the roots of wild grapevine Vitis vinifera spp. sylvestris

Transcriptional regulatory networks are pivotal components of plant's response to salt stress. However, plant adaptation strategies varied as a function of stress intensity, which is mainly modulated by climate change. Here, we determined the gene regulatory networks based on transcription factor (TF) TF_gene co-expression, using two transcriptomic data sets generated from the salt-tolerant "Tebaba" roots either treated with 50 mM NaCl (mild stress) or 150 mM NaCl (severe stress). The analysis of these regulatory networks identified specific TFs as key regulatory hubs as evidenced by their multiple interactions with different target genes related to stress response. Indeed, under mild stress, NAC and bHLH TFs were identified as central hubs regulating nitrogen storage process. Moreover, HSF TFs were revealed as a regulatory hub regulating various aspects of cellular metabolism including flavonoid biosynthesis, protein processing, phenylpropanoid metabolism, galactose metabolism, and heat shock proteins. These processes are essentially linked to short-term acclimatization under mild salt stress. This was further consolidated by the protein-protein interaction (PPI) network analysis showing structural and plant growth adjustment. Conversely, under severe salt stress, dramatic metabolic changes were observed leading to novel TF members including MYB family as regulatory hubs controlling isoflavonoid biosynthesis, oxidative stress response, abscisic acid signaling pathway, and proteolysis. The PPI network analysis also revealed deeper stress defense changes aiming to restore plant metabolic homeostasis when facing severe salt stress. Overall, both the gene co-expression and PPI network provided valuable insights on key transcription factor hubs that can be employed as candidates for future genetic crop engineering programs.

Transcriptome Profiling of a Salt Excluder Hybrid Grapevine Rootstock 'Ruggeri' throughout Salinity

Salinity is one of the substantial threats to plant productivity and could be escorted by other stresses such as heat and drought. It impairs critical biological processes, such as photosynthesis, energy, and water/nutrient acquisition, ultimately leading to cell death when stress intensity becomes uncured. Therefore, plants deploy several proper processes to overcome such hostile circumstances. Grapevine is one of the most important crops worldwide that is relatively salt-tolerant and preferentially cultivated in hot and semi-arid areas. One of the most applicable strategies for sustainable viticulture is using salt-tolerant rootstock such as Ruggeri (RUG). The rootstock showed efficient capacity of photosynthesis, ROS detoxification, and carbohydrate accumulation under salinity. The current study utilized the transcriptome profiling approach to identify the molecular events of RUG throughout a regime of salt stress followed by a recovery procedure. The data showed progressive changes in the transcriptome profiling throughout salinity, underpinning the involvement of a large number of genes in transcriptional reprogramming during stress. Our results established a considerable enrichment of the biological process GO-terms related to salinity adaptation, such as signaling, hormones, photosynthesis, carbohydrates, and ROS homeostasis. Among the battery of molecular/cellular responses launched upon salinity, ROS homeostasis plays the central role of salt adaptation.

Evidence of an active role of resveratrol derivatives in the tolerance of wild grapevines (Vitis vinifera ssp. sylvestris) to salinity

Resveratrol and its derivatives are the most important phytoalexins with a crucial role in plant defense mechanisms. These compounds can occur either naturally or in response to abiotic stresses. Among them, salinity is one of the major threats to the sustainability and productivity of agro-economically important species, particularly those involved in the vini-viticulture sector. Understating salinity tolerance mechanisms in plants is required for the development of novel engineering tools. This study aimed to investigate the potential role of resveratrol derivatives in salinity tolerance of wild grapevines. Our data revealed that the tolerant Tunisian wild grapevine genotype "Ouchtata" exhibited an increased accumulation of resveratrol derivatives (glycosylated and non-glycosylated resveratrol and t-ɛ-viniferin and hydroxylated t-piceatannol) in both stems and roots, along with an increased total antioxidant activity (TAA) compared to the sensitive genotype "Djebba" under stress conditions, suggesting an involvement of these stilbenes in redox homeostasis, thereby, protecting cells from salt-induced oxidative damage. Overall, our study revealed, for the first time, an active role for resveratrol derivatives in salt stress tolerance in wild grapevine, highlighting their potential use as metabolic markers in future grapevine breeding programs for a sustainable vini-viticulture in salt-affected regions.