'Corbarino' (COR) and 'Lucariello' (LUC) belong to the family of Mediterranean long shelf-life tomato landraces, producing high quality fruits under low water input cultivation regime in their traditional cultivation area. Understanding the morpho-physiological and molecular details of the peculiar drought stress tolerance of these two genotypes may be key to their valorization as breeding material. RNA sequencing of leaf samples of COR and LUC subjected to drought stress by water withholding in a semi-controlled greenhouse identified 3089 and 2135 differentially expressed genes respectively. These included COR- and LUC-specific annotated genes, as well as genes containing single nucleotide polymorphisms as compared to reference genome. Enriched Gene Ontology categories showed that categories such as response to water, oxidoreductase activity, nucleotide salvation and lipid biosynthesis-related processes were enriched among up-regulated DEGs. By contrast, growth and photosynthesis related genes were down-regulated after drought stress, consistent with leaf gas exchange and biomass accumulation measurements. Genes encoding cell wall degrading enzymes of the pectinase family were also down-regulated in drought stress conditions and upregulated in rewatering, indicating that cell wall composition/hardness is important for drought stress responses. Globally our results contribute to understanding the transcriptomic and physiological responses of representative tomato genotypes from Southern Italy, highlighting a promising set of genes to be investigated to improve tomato tolerance to drought.

Tomato is a horticultural crop of high economic and nutritional value. Suboptimal environmental conditions, such as limited water and nutrient availability, cause severe yield reductions. Thus, selection of genotypes requiring lower inputs is a goal for the tomato breeding sector. We screened 10 tomato varieties exposed to water deficit, low nitrate or a combination of both. Biometric, physiological and molecular analyses revealed different stress responses among genotypes, identifying T270 as severely affected, and T250 as tolerant to the stresses applied. Investigation of transcriptome changes caused by combined stress in roots and leaves of these two genotypes yielded a low number of differentially expressed genes (DEGs) in T250 compared to T270, suggesting that T250 tailors changes in gene expression to efficiently respond to combined stress. By contrast, the susceptible tomato activated approximately one thousand and two thousand genes in leaves and roots respectively, indicating a more generalized stress response in this genotype. In particular, developmental and stress-related genes were differentially expressed, such as hormone responsive factors and transcription factors. Analysis of differential alternative splicing (DAS) events showed that combined stress greatly affects the splicing landscape in both genotypes, highlighting the important role of AS in stress response mechanisms. In particular, several stress and growth-related genes as well as transcription and splicing factors were differentially spliced in both tissues. Taken together, these results reveal important insights into the transcriptional and posttranscriptional mechanisms regulating tomato adaptation to growth under reduced water and nitrogen inputs.

The Mediterranean basin countries are considered secondary centres of tomato diversification. However, information on phenotypic and allelic variation of local tomato materials is still limited. Here we report on the evaluation of the largest traditional tomato collection, which includes 1499 accessions from Southern Europe. Analyses of 70 traits revealed a broad range of phenotypic variability with different distributions among countries, with the culinary end use within each country being the main driver of tomato diversification. Furthermore, eight main tomato types (phenoclusters) were defined by integrating phenotypic data, country of origin, and end use. Genome-wide association study (GWAS) meta-analyses identified associations in 211 loci, 159 of which were novel. The multidimensional integration of phenoclusters and the GWAS meta-analysis identified the molecular signatures for each traditional tomato type and indicated that signatures originated from differential combinations of loci, which in some cases converged in the same tomato phenotype. Our results provide a roadmap for studying and exploiting this untapped tomato diversity.

Saline irrigation compromises the utility of agricultural soil, limiting ion uptake and productivity worldwide. Electromagnetic water might provide a possible solution to enhance ion mobilization. This study was conducted to investigate the effects of saline irrigation on yield, metabolism and some physiological traits of potato over two growing seasons. The drip experiment treatments comprised the following: saline water (SW), electromagnetic saline water (MSW) and ground water (C) applied to three potato varieties (Spunta, Bellini and Alaska) since vegetative growth stage (12 days after planting). Results showed that soil salinity was reduced by 25% under MSW relative to SW. Both C and MSW had a promotional effect on root growth. Tuber number was increased with MSW in Spunta and Alaska. The highest values of photosynthesis, water status attributes and ion content of Alaska variety were associated with an elevated StSOS1 expression level. The effective osmotic adjustment with proline for Spunta and Alaska varieties was associated with differential expression of proline synthesis (StP5CS1) and catabolism (StP5CDH) genes. Accordingly, Alaska seems to be more resistant to salinity than Spunta and Bellini, and electromagnetic water may be useful to enhance potato production in areas suffering from water salinization.

Modifications of the cellular proteome pool upon stress allow plants to tolerate environmental changes. Alternative splicing is the most significant mechanism responsible for the production of multiple protein isoforms from a single gene. The spliceosome, a large ribonucleoprotein complex, together with several associated proteins, controls this pre-mRNA processing, adding an additional level of regulation to gene expression. Deep sequencing of transcriptomes revealed that this co- or post-transcriptional mechanism is highly induced by abiotic stress, and concerns vast numbers of stress-related genes. Confirming the importance of splicing in plant stress adaptation, key players of stress signaling have been shown to encode alternative transcripts, whereas mutants lacking splicing factors or associated components show a modified sensitivity and defective responses to abiotic stress. Here, we examine recent literature on alternative splicing and splicing alterations in response to environmental stresses, focusing on its role in stress adaptation and analyzing the future perspectives and directions for research.

Anthocyanins are antioxidant pigments widely used in drugs and food preparations. Flesh-coloured tubers of the cultivated potato Solanum tuberosum are important sources of different anthocyanins. Due to the high degree of decoration achieved by acylation, anthocyanins from potato are very stable and suitable for the food processing industry. The use of cell culture allows to extract anthocyanins on-demand, avoiding seasonality and consequences associated with land-based-tuber production. However, a well-known limit of cell culture is the metabolic instability and loss of anthocyanin production during successive subcultures. To get a general picture of mechanisms responsible for this instability, we explored both genetic and epigenetic regulation that may affect anthocyanin production in cell culture. We selected two clonally related populations of anthocyanin-producing (purple) and non-producing (white) potato cells. Through targeted molecular investigations, we identified and functionally characterized an R3-MYB, here named StMYBATV. This transcription factor can interact with bHLHs belonging to the MBW (R2R3-MYB, bHLH and WD40) anthocyanin activator complex and, potentially, may interfere with its formation. Genome methylation analysis revealed that, for several genomic loci, anthocyanin-producing cells were more methylated than clonally related white cells. In particular, we localized some methylation events in ribosomal protein-coding genes. Overall, our study explores novel molecular aspects associated with loss of anthocyanins in cell culture systems.

RNA splicing is a fundamental mechanism contributing to the definition of the cellular protein population in any given environmental condition. DNA-DAMAGE REPAIR/TOLERATION PROTEIN 111/ SPLICING FACTOR FOR PHYTOCHROME SIGNALING (DRT111/SFPS) is a splicing factor previously shown to interact with phytochrome B and characterized for its role in splicing of pre-mRNAs involved in photomorphogenesis. Here, we show that DRT111 interacts with Arabidopsis thaliana Splicing Factor 1 (SF1), involved in 3? splicing site recognition. Double and triple mutant analysis shows that DRT111 controls splicing of ABI3 and acts upstream of the splicing factor SUPPRESSOR OF ABI3-5 (SUA). DRT111 is highly expressed in seeds and stomata of Arabidopsis and is induced by long-term treatments of polyethylene glycol and abscisic acid (ABA). DRT111 knock-out mutants are defective in ABA-induced stomatal closure and are hypersensitive to ABA during seed germination. Conversely, DRT111 over-expressing plants show ABA-hyposensitive seed germination. RNAseq experiments show that in dry seeds, DRT111 controls expression and splicing of genes involved in osmotic-stress and ABA responses, light signaling, and mRNA splicing, including targets of ABSCISIC ACID INSENSITIVE3 (ABI3) and PHYTOCHROME INTERACTING FACTORs (PIFs). Consistently, expression of the germination inhibitor SOMNUS, induced by ABI3 and PIF1, is up-regulated in imbibed seeds of drt111-2 mutants. Together, these results indicate that DRT111 controls sensitivity to ABA during seed development, germination, and stomatal movements, and integrates ABA- and light-regulated pathways to control seed germination.

Abscisic acid (ABA) plays an important role in various aspects of plant growth and development, including adaptation to stresses, fruit development and ripening. In seeds, ABA participates through its core signaling components in dormancy instauration, longevity determination, and inhibition of germination in unfavorable environmental conditions such as high soil salinity. Here, we show that seed germination in pepper was delayed but only marginally reduced by ABA or NaCl with respect to control treatments. Through a similarity search, pepper orthologs of ABA core signaling components PYL (PYRABACTIN RESISTANCE1-LIKE), PP2C (PROTEIN PHOSPHATASE2C), and SnRK2 (SUCROSE NONFERMENTING1 (SNF1)-RELATED PROTEIN KINASE2) genes were identified. Gene expression analyses of selected members showed a low abundance of PYL and SnRK2 transcripts in dry seeds compared to other tissues, and an upregulation at high concentrations of ABA and/or NaCl for both positive and negative regulators of ABA signaling. As expected, in hydroponically-grown seedlings exposed to NaCl, only PP2C encoding genes were up-regulated. Yeast two hybrid assays performed among putative pepper core components and with Arabidopsis thaliana orthologs confirmed the ability of the identified proteins to function in ABA signaling cascade, with the exception of a CaABl isoform cloned from seeds. BiFC assay in planta confirmed some of the interactions obtained in yeast. Altogether, our results indicate that a low expression of perception and signaling components in pepper seeds might contribute to explain the observed high percentages of seed germination in the presence of ABA. These results might have direct implications on the improvement of seed longevity and vigor, a bottleneck in pepper breeding.

Tomato (Solanum lycopersicum L.) is a high value horticultural crop and an important dietary source of nutrients, vitamins and antioxidants. The cultivation is often subjected to drought, salinity and N-limited conditions. Thus, understanding the responses of tomato to salt and low N conditions will be instrumental to improve yields in stress-prone environments. In this study, physiological and molecular responses of three Italian landraces (TRPO0040, TRPA0130 and TRPO0670) to salt stress and low nitrate, alone or in combination were analysed. The experimental set up allowed four different treatments named: Control (13.5 mM NO3- - 0 mM NaCl), Salt stress (13.5 mM NO3- - 80 mM NaCl), N stress (3.4 mM NO3-- 0 mM NaCl) and Combined stress (3.4 mM NO3- - 80 mM NaCl). The treatments had different effects on plants: low N caused chlorosis, while salt stress inhibited growth causing loss of basal leaves. Leaf relative water content was affected by both salt and low nitrate, depending on the genotype, while proline content was dramatically increased by salt stress but not under combined stress. Growth parameters and fruit yield were reduced by single stress condition, and the highest reduction was observed in the combined stress. TRPO0040 genotype showed high Nitrogen Use Efficiency and Nitrogen Utilization Efficiency under salt, indicating that nitrogen allocation to fruits was not affected by this stress. We evaluated the impact of single and combined stresses on tomato transcriptome by performing RNAseq on roots and leaves of TRPO0040 after long-term exposure to the treatments. In leaves, a more extensive transcriptome reorganization was observed in response to N stress, while salt induced a significant variation in gene expression of a handful of genes. Parallel to the proline levels, expression of P5CS gene, encoding the rate limiting proline biosynthetic enzyme, was induced by salt, while the catabolic proline dehydrogenase was suppressed. Similarly, several genes encoding nitrate transporters were induced in N stress, including NRT2;2 and others. By contrast, in roots several thousands of differentially expressed genes (DEGs) DEGs in salt stress and only few hundreds in N stress were identified. Consistent with results gathered in Arabidopsis, SLAH1, a gene encoding a root specific anion transporter involved in the long distance transport of MOLECULAR MECHANISMS UNDERLYING MORPHO- PHYSIOLOGICAL ADAPTATION TO COMBINED SALT/LOW NUTRIENT STRESS IN TOMATO chloride ions, was upregulated in roots in salt stress condition, while a NRT2;4 like and AMT1 were induced by low nitrate. In the combined stress, a more extensive overlap of the DEGs was observed with the N stress rather than the salt stress for both roots and leaves. This indicates that nutrient availability may have a higher and longer- term impact on gene expression, compared to salt stress, which may induce rapid and transient responses, attenuated, particularly in leaves, when plant adaptation occurs. Altogether, we show that different cultivation regimes affect metabolic and transcriptomic profiles as well as growth in tomato, identifying a set of physiological and molecular targets specifically influenced by single or combined stress.

Traditional varieties of tomato from the Mediterranean region represent a pool of biodiversity that can be mined for novel traits that can be used for the genetic improvement of commercial tomato varieties. As urban development and climate change exacerbate competition for water and critical resources, it is essential commercial production of vegetables increases the Water Use Efficiency (WUE) and Nutrient/Nitrate Use Efficiency (NUE) in order to reduce the environmental impacts in terms of water and fertilizer (Hirel et al., 2007; Erisman et al., 2008). In order to address the anticipated need for improvement of existing commercial varieties (Ruggiero et al., 2017), we are screening over 40 traditional tomato varieties for their WUE, NUE and combined stress indexes to identify genotypes that are particularly efficient in their use of water, nitrogen, or both these critical resources. The best performing genotypes will be further evaluated at the molecular and genetic level to determine which traits and genes are responsible for increased WUE and NUE.

Modulation of growth in response to environmental cues is a fundamental aspect of plant adaptation to abiotic stresses. TIP41 (TAP42 INTERACTING PROTEIN OF 41 kDa) is the Arabidopsis thaliana orthologue of proteins isolated in mammals and yeast that participate in the Target-of-Rapamycin (TOR) pathway, which modifies cell growth in response to nutrient status and environmental conditions. Here, we characterized the function of TIP41 in Arabidopsis. Expression analyses showed that TIP41 is constitutively expressed in vascular tissues, and is induced following long-term exposure to NaCl, polyethylene glycol and abscisic acid (ABA), suggesting a role of TIP41 in adaptation to abiotic stress. Visualization of a fusion protein with yellow fluorescent protein indicated that TIP41 is localized in the cytoplasm and the nucleus. Abolished expression of TIP41 results in smaller plants with a lower number of rosette leaves and lateral roots, and an increased sensitivity to treatments with chemical TOR inhibitors, indicating that TOR signalling is affected in these mutants. In addition, tip41 mutants are hypersensitive to ABA at germination and seedling stage, whereas over-expressing plants show higher tolerance. Several TOR- and ABA-responsive genes are differentially expressed in tip41, including iron homeostasis, senescence and ethylene-associated genes. In yeast and mammals, TIP41 provides a link between the TOR pathway and the protein phosphatase 2A (PP2A), which in plants participates in several ABA-mediated mechanisms. Here, we showed an interaction of TIP41 with the catalytic subunit of PP2A. Taken together, these results offer important insights into the function of Arabidopsis TIP41 in the modulation of plant growth and ABA responses.

Tomato is a high value crop and the primary model for fleshy fruit development and ripening. Breeding priorities include increased fruit quality, shelf life and tolerance to stresses. To contribute towards this goal, we re-sequenced the genomes of Corbarino (COR) and Lucariello (LUC) landraces, which both possess the traits of plant adaptation to water deficit, prolonged fruit shelf-life and good fruit quality. Through the newly developed pipeline Reconstructor, we generated the genome sequences of COR and LUC using datasets of 65.8M and 56.4M of 30-150bp paired-end reads, respectively. New contigs including reads that could not be mapped to the tomato reference genome were assembled, and a total of 43, 054 and 44, 579 gene loci were annotated in COR and LUC. Both genomes showed novel regions with similarity to Solanum pimpinellifolium and Solanum pennellii. In addition to small deletions and insertions, 2, 000 and 1, 700 single nucleotide polymorphisms (SNPs) could exert potentially disruptive effects on 1, 371 and 1, 201 genes in COR and LUC, respectively. A detailed survey of the SNPs occurring in fruit quality, shelf life and stress tolerance related-genes identified several candidates of potential relevance. Variations in ethylene response components may concur in determining peculiar phenotypes of COR and LUC.

Wild potato species are useful sources allelic diversity and loci lacking in the cultivated potato. In these species, the presence of anthocyanins in leaves has been associated with a greater tolerance to cold stress. However, the molecular mechanisms that allow potatoes to withstand cold exposure remain unclear. Here, we show that the expression of AN2, a MYB transcription factor, is induced by low temperatures in wild, cold tolerant Solanum commersonii, and not in susceptible S. tuberosum varieties. We found that AN2 is a paralog of the potato anthocyanin regulator AN1, showing similar interaction ability with bHLH co-partners. Their sequence diversity resulted in a different capacity to promote accumulation of phenolics when tested in tobacco. Indeed, functional studies demonstrated that AN2 is less able to induce anthocyanins than AN1, but nevertheless it has a strong ability to induce accumulation of hydroxycinnamic acid derivatives. We propose that the duplication of R2R3 MYB genes resulted in subsequent subfunctionalization, where AN1 specialized in anthocyanin production and AN2 conserved the ability to respond to cold stress, inducing mainly the synthesis of hydroxycinnamic acid derivatives. These results contribute to understanding the evolutionary significance of gene duplication on phenolic compound regulation.

In questo capitolo affronteremo il tema di come le piante rispondono alle sollecitazioni dell'ambiente circonstante. Le piante si sviluppano in un ambiente fisico in continuo cambiamento in termini di disponibilità idrica e di nutrienti, temperatura, intensità luminosa e presenza di elementi fitotossici. Quando tali variazioni raggiungono un livello soglia inducono uno stress, causando un effetto negativo sul normale programma di sviluppo vegetale, e con gravi ricadute in termini di produttività in agricoltura. L' ottenimento di varietà adatte alle variazioni climatiche previste nei prossimi decenni rappresenta una priorità per lo sviluppo e il sostentamento del genere umano. In una prima parte del capitolo definiremo i vari tipi di stress a cui una pianta può essere soggetta e come tale stress viene interpretato dalla pianta stessa. In particolare ci soffermeremo sugli effetti indotti dalla siccità, la salinità e le temperature estreme. Definiremo quindi le variazioni indotte da questi stress sulle piante, in termini fisiologici, metabolici e morfologici. In una seconda parte del capitolo, illustreremo la base genetica e molecolare delle risposte adattative della pianta ai vari tipi di stress. Ci concentreremo in larga parte su esperimenti altamente significativi realizzati su sistemi modello utilizzando un approccio di casi studio. L'uso di strategie diverse quali la genetica inversa e di popolazione, la biologia molecolare e i più recenti approcci di chemical genomics, ha permesso di definire l'identità di geni chiave coinvolti nella risposta e adattamento ai diversi tipi di stress, e che sono quindi da considerarsi candidati ideali da ottimizzare per ottenere piante maggiormente tolleranti. Illustreremo inoltre quali sono le risposte agli stress riscontrate nelle piante nel loro ambiente naturale, chiariremo quali di esse sono state selezionate dall'uomo attraverso la domesticazione nel corso dei millenni e quali sono state invece eliminate nelle moderne varieta' e il motivo di questa selettività. Basandoci su questo bagaglio di conoscenze teoriche e tecniche, concluderemo questo capitolo discutendo quali approcci possono essere utilizzati per rendere le piante più tolleranti allo stress, portando ad esempio alcuni prototipi sperimentali e varietà già in commercio.

Vegetables include high-value crops with health-promoting effects and reduced environmental impact. The availability of genomic and biotechnological tools in certain species, coupled with the recent development of new breeding techniques based on precise editing of DNA, provides unique opportunities to finally take advantage of the past decades of detailed genetic analyses, thus making improvement of traits related to quality and stress tolerance achievable in a reasonable time frame. Recent reports of such approaches in vegetables illustrate the feasibility of obtaining multiple homozygous mutations in a single generation, heritable by the progeny, using stable or transient transformation approaches, which may not rely on the integration of unwanted foreign DNA. Application of these approaches to currently non-sequenced/tissue culture recalcitrant crops will contribute to meet the challenges posed by the increase in population and climate change.

Tomato (Solanum lycopersicum L.) is an important horticultural crop and a significant source of antioxidants in our diet. Yields suffer losses due to environmental stresses, including drought and salinity, which are among the most significant challenges for the future of global food production. Reduction of fertilizer inputs, including nitrate is also a priority in plant research, and it is aimed at minimizing pollution caused by agricultural activities, while obtaining fruits of high quality and long storability. In this study, we analysed vegetative and molecular responses of three tomato landraces (TRPO0040, TRPA0130 and TRPO0670) challenged with salt stress and low nitrate, alone or in combination, and their effects on fruit yield, quality and storability. The experiment was setup in a closed soilless system, in greenhouse, using four different conditions: N1S0: 13.5 mM NO3- - 0 mM NaCl; N1S1: 13.5 mM NO3- - 80 mM NaCl; N0S0: 3.4 mM NO3-- 0 mM NaCl; N0S1: 3.4 mM NO3- - 80 mM NaCl. Several parameters were monitored during the vegetative phase, including stomatal conductance, leaf relative water and proline content, expression of selected ion transporter genes. Relative water content was affected by both salt and nitrate concentration, while proline content was dramatically increased by salt stress in high nitrate condition only. Growth parameters as well as fruit yield were reduced in the presence of stress, with the highest reduction observed in plants exposed to the combined stress. Highest yields were obtained in N1S0, however fruits harvested from low nutrient-treated plants were virtually all marketable, regardless the presence of NaCl. Soluble solids content was highly affected by salt, as expected. The cultivation regime also affected fruit shelf life of the three genotypes over the 90-day period monitored. High salt in the nutrient solution improved fruit shelf life regardless of genotype and nitrate concentration. In the absence of NaCl, NO3- supply in the nutrient solution did not affect fruit shelf life in TRPO0670 and TRPA0130, while TRPO0040 fruits showed an extended shelf life at low nitrate compared to high nitrate supply. Fruit firmness and weight declined in all genotypes and treatments during post-harvest; hence, they were not ?? RUGGIERO A.*, BATELLI G.*, VENEZIA A. ??NURCATO R.*, COSTA A.*, ?? discriminating parameters between treatments. Nitrogen Use Efficiency (NUE) evaluation in all treatments and landraces revealed that TRPO0040 maintained high NUE under salt stress, indicating that N allocation to fruits was not inhibited by salt in this genotype. Altogether, we have verified that different cultivation regimes affect fruit shelf life and quality in tomato, and identified a set of vegetative parameters specifically influenced by single or combined stress. In addition, RNAseq and qRT-PCRs analyses are being pursued in order to get further insights into the molecular basis of fruit shelf life under different cultivation regimes.

Background Drought is a major constraint for plant growth and crop productivity that is receiving an increased attention due to global climate changes. Chloroplasts act as environmental sensors, however, only partial information is available on stress-induced mechanisms within plastids. Here, we investigated the chloroplast response to a severe drought treatment and a subsequent recovery cycle in tomato through physiological, metabolite and proteomic analyses. Results Under stress conditions, tomato plants showed stunted growth, and elevated levels of proline, abscisic acid (ABA) and late embryogenesis abundant gene transcript. Proteomics revealed that water deficit deeply affects chloroplast protein repertoire (31 differentially represented components), mainly involving energy-related functional species. Following the rewatering cycle, physiological parameters and metabolite levels indicated a recovery of tomato plant functions, while proteomics revealed a still ongoing adjustment of the chloroplast protein repertoire, which was even wider than during the drought phase (54 components differentially represented). Changes in gene expression of candidate genes and accumulation of ABA suggested the activation under stress of a specific chloroplast-to-nucleus (retrograde) signaling pathway and interconnection with the ABA-dependent network. Conclusions Our results give an original overview on the role of chloroplast as enviromental sensor by both coordinating the expression of nuclear-encoded plastid-localised proteins and mediating plant stress response. Although our data suggest the activation of a specific retrograde signaling pathway and interconnection with ABA signaling network in tomato, the involvement and fine regulation of such pathway need to be further investigated through the development and characterization of ad hoc designed plant mutants.

Water-limiting conditions affect dramatically plant growth and development and, ultimately, yield of potato plants (Solanum tuberosum L.). Therefore, understanding the mechanisms underlying the response to water deficit is of paramount interest to obtain drought tolerant potato varieties. Herein, potato 10 K cDNA array slides were used to profile transcriptomic changes of two potato cell populations under abrupt (shocked cells) or gradual exposure (adapted cells) to polyethylene glycol (PEG)-mediated water stress. Data analysis identified > 1000 differentially expressed genes (DEGs) in our experimental conditions. Noteworthy, our microarray study also suggests that distinct gene networks underlie the cellular response to shock or gradual water stress. On the basis of our experimental findings, it is possible to speculate that DEGs identified in shocked cells participate in early protective and sensing mechanisms to environmental insults, while the genes whose expression was modulated in adapted cells are directly involved in the acquisition of a new cellular homeostasis to cope with water stress conditions. To validate microarray data obtained for potato cells, the expression analysis of 21 selected genes of interest was performed by Real-Time Quantitative Reverse Transcription PCR (qRT-PCR). Intriguingly, the expression levels of these transcripts in 4-week old potato plants exposed to long-term water-deficit. qRT-PCR analysis showed that several genes were regulated similarly in potato cells cultures and tissues exposed to drought, thus confirming the efficacy of our simple experimental system to capture important genes involved in osmotic stress response. Highlighting the differences in gene expression between shock-like and adaptive response, our findings could contribute to the discussion on the biological function of distinct gene networks involved in the response to abrupt and gradual adaptation to water deficit. (C) 2016 Elsevier B.V. All rights reserved.