Sugars Will Eventually be Exported Transporters (SWEETs) have important roles in numerous physiological mechanisms where sugar efflux is critical, including phloem loading, nectar secretion, seed nutrient filling, among other less expected functions. They mediate low affinity and high capacity transport, and in angiosperms this family is composed by 20 paralogs on average. As SWEETs facilitate the efflux of sugars, they are highly susceptible to hijacking by pathogens, making them central players in plant–pathogen interaction. For instance, several species from the Xanthomonas genus are able to upregulate the transcription of SWEET transporters in rice (Oryza sativa), upon the secretion of transcription-activator-like effectors. Other pathogens, such as Botrytis cinerea or Erysiphe necator, are also capable of increasing SWEET expression. However, the opposite behavior has been observed in some cases, as overexpression of the tonoplast AtSWEET2 during Pythium irregulare infection restricted sugar availability to the pathogen, rendering plants more resistant. Therefore, a clear-cut role for SWEET transporters during plant–pathogen interactions has so far been difficult to define, as the metabolic signatures and their regulatory nodes, which decide the susceptibility or resistance responses, remain poorly understood. This fuels the still ongoing scientific question: what roles can SWEETs play during plant–pathogen interaction? Likewise, the roles of SWEET transporters in response to abiotic stresses are little understood. Here, in addition to their relevance in biotic stress, we also provide a small glimpse of SWEETs importance during plant abiotic stress, and briefly debate their importance in the particular case of grapevine (Vitis vinifera) due to its socioeconomic impact.

The main goal of this study was to chemically characterize an aqueous S. nigra flower extract and validate it as a bioactive agent. The elderflower aqueous extraction was performed at different temperatures (50, 70 and 90 °C). The extract obtained at 90 °C exhibited the highest phenolic content and antiradical activity. Therefore, this extract was analyzed by GC-MS and HPLC-MS, which allowed the identification of 46 compounds, being quercetin and chlorogenic acid derivatives representative of 86% of the total of phenolic compounds identified in hydrophilic fraction of the aqueous extract. Naringenin (27.2%) was the major compound present in the lipophilic fraction. The antiproliferative effects of the S. nigra extract were evaluated using the colon cancer cell lines RKO, HCT-116, Caco-2 and the extract’s antigenotoxic potential was evaluated by the Comet assay in RKO cells. The RKO cells were the most susceptible to S. nigra flower extract (IC₅₀ = 1250 µg mL⁻¹). Moreover, the extract showed antimicrobial activity against Gram-positive bacteria, particularly Staphylococcus aureus and S. epidermidis. These results show that S. nigra-based extracts can be an important dietary source of bioactive phenolic compounds that contribute to health-span improving life quality, demonstrating their potential as nutraceutical, functional foods and/or cosmetic components for therapeutic purposes.

In grapes under drought stress, polyols accumulate through tight coordination at the molecular level between increased membrane transport of polyols and inhibition of polyol oxidation. Here, the effects on grape metabolism of an exogenous foliar application of polyols as a potential sustainable viticultural practice to increase grapevine performance and berry quality were thoroughly assessed. Grapevines were pulverised with a polyol solution containing 2 mM mannitol and 2 mM sorbitol, and the metabolome of grape berry exocarps and important metabolic pathways associated with berry quality and polyol metabolism were analysed at véraison and mature stages. By combining metabolomics analysis using UPLC-MS, enzyme activity assays and targeted transcriptional analyses, it was demonstrated that foliar application of polyols stimulated by 3.5-fold and 6-fold abscisic acid (ABA) biosynthesis at véraison and mature grape berries, respectively. It also stimulated the concentration of anthocyanins, stilbenes and total phenolics in exocarps through the upregulation of phenylpropanoid, stilbenoid and anthocyanin biosynthetic pathways shown by increases in phenylalanine-ammonia lyase (PAL) activity (3-fold) and VviPAL1 expression, stilbene synthase 1 (VviSTS1) transcripts (ca. 5-fold), UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) activity and VviUFGT1 expression, among other results, at the mature stage, when these changes were most noticeable. Many secondary metabolites synthesised in these pathways identified by UPLC-MS analysis were present at higher quantities in exocarps from polyol-treated plants such as fertaric acid, E-resveratrol, E-piceatannol, piceid, pallidol, E-ε-viniferin, myricetin-hexoside 1, cyanidin-3-O-glucoside and malvidin-3-O-(6-p-coumaroyl)-glucoside. Foliar application of low-concentration polyols is, therefore, a promising biostimulant-based strategy to improve grape berry quality and nutritional value in the current context of climate change.

The phenylpropanoid and flavonoid pathways exhibit intricate regulation, not only influenced by environmental factors and a complex network of transcription factors but also by post-transcriptional regulation, such as silencing by microRNAs and miRNA-encoded micropeptides (miPEPs). VviMYBC2-L1 serves as a transcriptional repressor for flavonoids, playing a crucial role in coordinating the synthesis of anthocyanin and proanthocyanidin. It works in tandem with their respective transcriptional activators, VviMYBA1/2 and VviMYBPA1, to maintain an equilibrium of flavonoids. We have discovered a miPEP encoded by miR166c that appears to target VviMYBC2-L1. We conducted experiments to test the hypothesis that silencing this transcriptional repressor through miPEP166c would stimulate the synthesis of anthocyanins and proanthocyanidins. Our transcriptional analyses by qPCR revealed that the application of exogenous miPEP166c to Gamay Fréaux grape berry cells resulted in a significant upregulation in flavonoid transcriptional activators (VviMYBA1/2 and VviMYBPA1) and structural flavonoid genes (VviLDOX and VviDFR), as well as genes involved in the synthesis of proanthocyanidins (VviLAR1 and VviANR) and anthocyanins (VviUFGT1). These findings were supported by the increased enzyme activities of the key enzymes UFGT, LAR, and ANR, which were 2-fold, 14-fold, and 3-fold higher, respectively, in the miPEP166c-treated cells. Ultimately, these changes led to an elevated total content of anthocyanins and proanthocyanidins.