Copper impacts on grape berry cells: uptake and detoxification

Copper has been extensively used as the active principle of fungicides, since the late 1800s when the “Bordeaux mixture” was developed and its spectacular efficiency proved against fungal pathogens such as downy mildew, which is a large threat to winegrowers. Although initially it seemed to improve plant growth in unproductive lands, repeated use of copper-based fungicides has led to the accumulation of large concentrations of this metal ion in vineyard soils and raised concerns regarding phytotoxicity. As major targets for heavy metal stress, plants have developed a number of mechanisms to withstand the elevated metal levels. Such responses include exclusion, chelation and compartmentation of metal ions. Both the mitochondria and plastids are copper sinks, and the vacuole is believed to constitute a copper delivery pathway within the cell, and not just a sequestration compartment, due to the proximity of the tonoplast to the other organelles of the plant cell. In the present study, grape berry cells (cv. Cabernet Sauvignon) were used as a model system to study the effect of copper on cell growth and viability. In the concentration range of 0 (+ the copper chelator BCS) to 100 μM CuSO4 growth was virtually unaffected. However, concentrations from 100 to 500 μM caused a sharp decrease in cell growth. The viability of grown cells decreased with the increase in copper concentration in a dose-dependent manner. Studies with the copper-sensitive fluorescent probe PhenGreen™ SK allowed for the identification of copper sinks in grape berry cells. Furthermore, transport studies were performed in isolated intact protoplasts loaded with this probe. The initial velocities of fluorescence quenching upon addition of copper followed a Michaelis-Menten kinetics, suggesting the involvement of mediated transport with a Km= 0.7 mM. Isolated vacuoles labeled with the pH-dependent fluorescent dye ACMA were used to study copper compartmentation as a mean of metal tolerance. Results showed that CuCl2 dissipates a pre-established pH gradient across the tonoplast suggesting the involvement of a Cu2+/H+ antiport system. Eight putative VvCTr (Vitis vinifera Copper Transporter) genes were identified, among which VvCTr1 was isolated and cloned and its expression is currently being studied.VM is supported by a PhD grant (SFRH/BD/64587/2009). This work was supported by Fundação para a Ciência e a Tecnologia (research project no. PTDC/AGRALI/100636/2008)

Improving germination and growth performances of millet grown under saline conditions through seed priming

L’amorçage (priming) est une technique de traitement pré-germinatif qui consiste  à imbiber la semence puis à la re-déshydrater avant la percée de la radicule. Notre travail consiste à étudier l’effet de deux agents de prétraitement des graines, notamment le PEG (20%) et l’AG3 (50 ppm) sur les performances germinatives, la croissance et l’hydratation des plantules de mil cultivées en présence de 100 mM NaCl. Notre objectif principal consiste à améliorer le phénotype et le comportement du mil cultivé sous contrainte saline via l’optimisation de l’amorçage des semences. Les résultats obtenus montrent que tous les types d’amorçage ont un effet bénéfique. Toutefois, le prétraitement des graines avec l’AG3 semble fortement associé à des processus mettant en jeu la croissance. Ce composé stimule de 100% la germination dès le 6ème jour de mise en germination en milieu salin. Cet effet est accompagné d’une amélioration de la croissance (193%) et d’une meilleure hydratation (330%), relativement aux plantes témoins. Cette réponse est primordialement liée à une capacité de détecter rapidement le stress salin et de le rendre facilement interprétable et même bénéfique pour sa croissance en milieux extrêmes

Interactive Effects of Cd and NaCl on Growth and Mineral Nutrition in Hordeum vulgare L. (Var. Raihane)

In this work, we investigated the combined effect of salt and cadmium on plant nutrition and Cd accumulation in the most cultivated barley variety in Tunisia, Raihane. Seedling were hydroponically subjected to four different treatment: the control without salt and Cd, 50mM NaCl alone, 10µM Cd alone and to the combination of Cd (10 µM) and NaCl (50 mM) during 1 month. At the harvest, plant growth, Cd content in shoots and roots and tissue nutrient concentrations in shoots(Ca, Fe, Mn and Zn) were measured. 50 mM NaCl alone does not significantly affected the morphology and the biomass of plants. However, when subjected to 10 µM Cd alone, plants of barley were less developed and produced low biomass as compared to control ones. NaCl addition to the Cd-treated plants further reduces the development and biomass production. With respect to nutrient acquisition results showed that NCl alone reduced Ca2+ and Fe2+ concentration in the shoots but not affected that of Zn and Mn. But Cd, applied alone or combined with NaCl disturbed all measured element concentration in the shoots. However, the addition of salt to the Cd-containing medium reduced significantly Cd accumulation in the roots and the shoots of plants. In conclusion, salt in the water irrigation is able to reduce Cd accumulation in this barley variety but it accentuated in the same time the toxic effect of this heavy metal in barley. View Article DOI: 10.47856/ijaast.2022.v09i10.00

Isolation and molecular characterization of ERF1, an ethylene response factor gene from durum wheat (Triticum turgidum L. subsp. durum), potentially involved in salt-stress responses

As food crop, wheat is of prime importance for human society. Nevertheless, our understanding of the genetic and molecular mechanisms controlling wheat productivity conditions has been, so far, hampered by the lack of sufficient genomic resources. The present work describes the isolation and characterization of TdERF1, an ERF gene from durum wheat (Triticum turgidum L. subsp. durum). The structural features of TdERF1 supported the hypothesis that it is a novel member of the ERF family in durum wheat and, considering its close similarity to TaERF1 of Triticum aestivum, it probably plays a similar role in mediating responses to environmental stresses. TdERF1 displayed an expression pattern that discriminated between two durum wheat genotypes contrasted with regard to salt-stress tolerance. The high number of cis-regulatory elements related to stress responses present in the TdERF1 promoter and the ability of TdERF1 to regulate the transcription of ethylene and drought-responsive promoters clearly indicated its potential role in mediating plant responses to a wide variety of environmental constrains. TdERF1 was also regulated by abscisic acid, ethylene, auxin, and salicylic acid, suggesting that it may be at the crossroads of multiple hormone signalling pathways. Four TdERF1 allelic variants have been identified in durum wheat genome, all shown to be transcriptionally active. Interestingly, the expression of one allelic form is specific to the tolerant genotype, further supporting the hypothesis that this gene is probably associated with the susceptibility/tolerance mechanism to salt stress. In this regard, the TdERF1 gene may provide a discriminating marker between tolerant and sensitive wheat varieties

Effect of water and salt stresses on germination of some acacia species in Tunisia

This work has focused on the study of germination characteristics of seeds of Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan, a species native of Tunisia, and of two introduced species : Acacia salicina Lindl. and Acacia ampliceps Maslin, reforested in arid zones of Tunisia. Germination was followed under conditions of water and salt stresses. Pre-treatments designed to remove integumentary inhibitions were applied to seeds. The germination behaviour of acacias in osmotic stress conditions showed a treatment effect, concentration of PEG 6000, highly significant on germination rate and mean time of germination. We found that these species did not tolerate drought and we observed a complete inhibition of germination at -0.8 MPa. The study of the effect of salt stress on germination showed a better tolerance of Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan to salinity than the other two species as it germinated at high salt concentrations. Indeed, at 18 g/l the germination rate reached 32 %. We didn’t find any relationship between seed germinative properties and ecology of the adult plantNotre travail a porté sur l'étude des caractéristiques germinatives des semences d'Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan, espèce autochtone de la Tunisie et deux espèces introduites Acacia salicina Lindl. et Acacia ampliceps Maslin qui sont utilisées en reboisement dans les zones arides de la Tunisie. La germination a été suivie en conditions de stress hydrique et salin. Des prétraitements destinés à lever les inhibitions tégumentaires ont été appliqués aux semences. Le comportement germinatif des acacias en conditions de stress osmotique a mis en évidence un effet traitement hautement significatif concernant le taux de germination et le temps moyen de germination. Nous avons révélé que ces espèces ne tolèrent pas la sécheresse et nous avons observé une inhibition totale de germination à -0.8 MPa. L'étude de la contrainte saline sur la germination a révélé une meilleure tolérance à la salinité de l'Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan par rapport au deux autres espèces puisqu'il a germé à des concentrations élevées de sel. En effet, à 18 g/l le taux de germination atteint 32 %. Enfin nos travaux n'ont pas mis en évidence de relation entre les propriétés germinatives des semences et l'écologie de la plante au stade adulte

Quality selection and genetic diversity of Tunisian durum wheat varieties using SSR markers

Our study focuses on the molecular analysis of the genetic diversity within 15 Tunisian durum wheat varieties and the assessment of the efficiency of some available markers to select valuable genotypes for technological proprieties of semolina (i.e. parameters related to SDS-sedimentation, mixing time and breakdown resistance of mixograph, grain protein content and yellow colour). While several markers were validated, others were not informative within the genotypes used. A high level of polymorphic information content (PIC) was detected, with an average of 5.2 polymorph alleles per locus and 0.6 average. Old varieties have high protein content however; modern varieties display strong gluten strength. Our results thus open the opportunity to choose valuable parents on the base of pedigrees, technological properties and genetic distances; and lead us to select efficient markers for the Regional Indigenous Land Strategy (Rils) selection strategy

Evaluation of the morpho-physiological, biochemical and molecular responses of contrasting Medicago truncatula lines under water deficit stress

This article belongs to the Special Issue Molecular Analysis of Medicago Spp.Medicago truncatula is a forage crop of choice for farmers, and it is a model species for molecular research. The growth and development and subsequent yields are limited by water availability mainly in arid and semi-arid regions. Our study aims to evaluate the morpho-physiological, biochemical and molecular responses to water deficit stress in four lines (TN6.18, JA17, TN1.11 and A10) of M. truncatula. The results showed that the treatment factor explained the majority of the variation for the measured traits. It appeared that the line A10 was the most sensitive and therefore adversely affected by water deficit stress, which reduced its growth and yield parameters, whereas the tolerant line TN6.18 exhibited the highest root biomass production, a significantly higher increase in its total protein and soluble sugar contents, and lower levels of lipid peroxidation with greater cell membrane integrity. The expression analysis of the DREB1B gene using RT-qPCR revealed a tissue-differential expression in the four lines under osmotic stress, with a higher induction rate in roots of TN6.18 and JA17 than in A10 roots, suggesting a key role for DREB1B in water deficit tolerance in M. truncatula.This study was supported by the Tunisian Ministry of Higher Education and Scientific Research (CBBC02 LR15) and the National Research Foundation of South Africa (GUN 95358) in the framework of the Tunisian-South African Joint Research Collaboration Program (2016–2017).Peer reviewe

Discovering new genes for alfalfa (Medicago sativa) growth and biomass resilience in combined salinity and Phoma medicaginis infection through GWAS

Salinity and Phoma medicaginis infection represent significant challenges for alfalfa cultivation in South Africa, Europe, Australia, and, particularly, Tunisia. These constraints have a severe impact on both yield and quality. The primary aim of this study was to establish the genetic basis of traits associated with biomass and growth of 129 Medicago sativa genotypes through genome-wide association studies (GWAS) under combined salt and P. medicaginis infection stresses. The results of the analysis of variance (ANOVA) indicated that the variation in these traits could be primarily attributed to genotype effects. Among the test genotypes, the length of the main stem, the number of ramifications, the number of chlorotic leaves, and the aerial fresh weight exhibited the most significant variation. The broad-sense heritability (H²) was relatively high for most of the assessed traits, primarily due to genetic factors. Cluster analysis, applied to morpho-physiological traits under the combined stresses, revealed three major groups of accessions. Subsequently, a GWAS analysis was conducted to validate significant associations between 54,866 SNP-filtered single-nucleotide polymorphisms (SNPs) and seven traits. The study identified 27 SNPs that were significantly associated with the following traits: number of healthy leaves (two SNPs), number of chlorotic leaves (five SNPs), number of infected necrotic leaves (three SNPs), aerial fresh weight (six SNPs), aerial dry weight (nine SNPs), number of ramifications (one SNP), and length of the main stem (one SNP). Some of these markers are related to the ionic transporters, cell membrane rigidity (related to salinity tolerance), and the NBS_LRR gene family (associated with disease resistance). These findings underscore the potential for selecting alfalfa genotypes with tolerance to the combined constraints of salinity and P. medicaginis infection