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Peroxiredoxins (Prxs) are ubiquitous peroxidases that can remove excess of free radicals produced under stress conditions, thereby protecting cells from oxidative damage. They are also involved in reactive oxygen species (ROS) and redox-dependent signaling by performing redox interactions with other proteins and altering their redox status. Here, Prx gene families (Prxs) were identified in the trio of Brachypodium species (B. distachyon, B. stacei and B. hybridium) using bioinformatic tools and classified into four distinct groups based on the phylogenetic analysis. Analysis of their subcellular locations showed that the majority of which were mainly located in the chloroplast and mitochondria. In silico expression analysis showed that BdPrxs genes are tissue-specific. RT-qPCR analysis of BdPrxs genes revealed their differential expression in B. distachyon when exposed to salt or drought stresses. In addition, the upregulation of BdPrx genes was accompanied by an accumulation of hydrogen peroxide (H2O2). The exogenous application of H2O2 induced the expression of almost all BdPrxs genes in both leaves and roots of B. distachyon plants. Overall, our results indicate the functional specificity for BdPrxs beside their potential role in development, and abiotic stress response presumably via the maintenance of redox homeostasis. Our data provided a solid basis for further studies on the biological functions of Prx genes in B. distachyon and other monocotyledonous plants.

Salinity is a brutal environmental factor that severely affects barley growth and development. In this context, local landraces, commonly cultivated under stressful conditions, could represent important reservoirs of valuable traits in barley breeding programs. Therefore, understanding salt-tolerance mechanisms in such genotypes is of great interest. Here, based on a 2D-PAGE comparative proteomic study, salt-induced proteome changes were explored in the seedling leaves of two contrasting Tunisian landraces, namely Boulifa (tolerant) and Testour (sensitive). The analysis showed that 11 salt-responsive proteins were differentially accumulated in both accessions under salt stress and 43 were genotype-specific (18 in Boulifa and 25 in Testour). Using mass spectrometry identification and annotation, 11 function categories revealed being involved in salt-stress response, specifically the defense/cell wall related metabolism. In fact, a chitinase, was up-regulated in the tolerant accession and down-regulated in the sensitive one in addition to a ricin B-like lectin R40G3 as well as a predicted BSP that were up-regulated in the tolerant one. Then, two other chitinases, PR10, glucan endo-1.3-β-glucosidase, were down-regulated in Testour, while still unchanged in the tolerant accession Boulifa. In the latter, signaling, redox/polyamine catabolism and the energy metabolism were found as part of the biochemical pathways underlying salt-tolerance. These results suggest that Boulifa may alleviate salt stress by activation of specific defense responses, and adjustment of both redox/polyamine catabolism and energy metabolism processes. Our findings represent a basis that would assist selection of candidates as markers in improving barley salt tolerance and elite genotypes creation.

The characterization of PR10 proteins has been conducted in many plant species. However, little is known about the roles of PvPR10 in response of common bean (Phaseolus vulgaris L.) to stress. Thus, for the first time a genome wide analysis revealed that the 34 genes of Bet v 1 family were divided into three major subfamilies according to phylogenetic relationship analysis from P. vulgaris and other plant species. The analysis uncovered that tandem duplication was the major force in the expansion of the Bet v 1 family genes in P. vulgaris and two other Fabaceae plants. Furthermore, the gene structure and motifs examination revealed that genes of Bet v 1 family were relatively conserved during evolution. Likewise, we recognized in the PvPR10 promoter regions several cis-regulatory elements related not only to abiotic and biotic stresses but also to phytohormones. In P. vulgaris, several PvPR10 genes exhibited differential expression profiles in many developmental tissues and organs. Notably, the expression profiles showed that essentially the two genes PvPR10-2 and PvPR10-3 genes were up-regulated under various treatments. Besides, the combined NaCl-JA stress enhanced their expressions in leaves and stems. Finally, we noticed that these inductions seem to be correlated with the enhancement of the expression of ABA biosynthesis PvNCED3 gene and the transcription factor PvDREB. Taken together, these data provide a foundation for further functional studies of certain PvPR10 that could be used in various stress tolerance improvements.

Arid and semi-arid areas are considered vulnerable to various environmental constraints which are further fortified by climate change. Salinity is one of the most serious abiotic factors affecting crop yield and soil fertility. Till now, no information is available on the effect of salinity on development and symbiotic nitrogen (N(2)) fixation in the legume species Lathyrus cicera. Here, we evaluated the effect of different microbial inocula including nitrogen-fixing Rhizobium laguerreae, arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis, a complex mixed inoculum of AMF isolated from rhizospheric soil in “Al Aitha”, and various plant growth-promoting bacteria (PGPB) including Bacillus subtilus, Bacillus simplex and Bacillus megaterium combined with Rhizobium, the AMF consortium, or R. irregularis on alleviating salt stress in this legume. A pot trial was conducted to evaluate the ability of different microbial inocula to mitigate adverse effects of salinity on L. cicera plants. The results showed that salinity (100 mM NaCl) significantly reduced L. cicera plant growth. However, inoculation with different inocula enhanced plant growth and markedly promoted various biochemical traits. Moreover, the combined use of PGPB and AMF was found to be the most effective treatment in mitigating deleterious effects of salinity stress on L. cicera. In addition, this co-inoculation upregulated the expression of two marker genes (LcHKT1 and LcNHX7) related to salinity tolerance. Our findings suggest that the AMF/PGPB formulation has a great potential to be used as a biofertilizer to improve L. cicera plant growth and productivity under saline conditions. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-022-01205-4.

Drought stress is one of the most prevalent environmental factors limiting faba bean (Vicia faba L.) crop productivity. β-aminobutyric acid (BABA) is a non-protein amino acid that may be involved in the regulation of plant adaptation to drought stress. The effect of exogenous BABA application on physiological, biochemical and molecular responses of faba bean plants grown under 18% PEG-induced drought stress were investigated. The results showed that the application of 1 mM of BABA improved the drought tolerance of faba bean. The application of BABA increased the leaf relative water content, leaf photosynthesis rate (A), transpiration rate (E), and stomatal conductance (gs), thereby decreased the water use efficiency. Furthermore, exogenous application of BABA decreased production of hydrogen peroxide (H2O2), malondialdehyde and electrolyte leakage levels, leading to less cell membrane damage due to oxidative stress. Regarding osmoprotectants, BABA application enhanced the accumulation of proline, and soluble sugars, which could improve the osmotic adjustment ability of faba bean under drought challenge. Interestingly, mended antioxidant enzyme activities like catalase, guaiacol peroxidase, ascorbate peroxidase and superoxide dismutase and their transcript levels may lead to counteract the damaging effects of oxidative stress and reducing the accumulation of harmful substances in BABA-treated faba bean plants. In addition, exogenous BABA significantly induced the accumulation of drought tolerance-related genes like VfMYB, VfDHN, VfLEA, VfERF, VfNCED, VfWRKY, VfHSP and VfNAC in leaves and roots, suggesting that BABA might act as a signal molecule to regulate the expression of drought tolerance-related genes.

Glutaredoxins (Grxs) are ubiquitous oxidoreductase proteins implicated in development and abiotic stress response mainly through maintaining redox homoeostasis. Here, we conducted the first systematic analysis of the Grx gene family (PvGrx) in the most popular legume Phaseolus vulgaris (common bean). A total of 50 PvGrx genes were identified, and divided into four classes (CC-type, CGFS-type, CPYC-type and Grl-type) based on the phylogenetic analysis. The different classes have different introns-exons structures and conserved motifs, indicating functional divergence in the PvGrx family. Both tandem and segmental duplications were found to be involved in the expansion of PvGrx family that underwent a purifying selection by excluding the deleterious loss-of-function mutations. Cis-acting regulatory elements and gene ontology analyses predicted their role of distinctive members in abiotic stress response and hormonal signalling. RNA-seq based expression analysis revealed their differential expression pattern during plant development. On the other hand, RT q-PCR analysis revealed that target PvGrx isoforms were associated with nodule organogenesis and symbiosis based on their expression profiles. In addition, a battery of PvGrx candidates were markedly upregulated by different abiotic stressors suggesting their broad spectrum of functions. These findings serve as a reference for functional analysis and genetic improvement in P. vulgaris and related legume species.

Peroxiredoxins (Prxs) are novel cysteine-based peroxidases which are involved in protecting cells from oxidative damage by catalyzing the reduction of different peroxides. The present study addressed, for the first time, genome-wide identification, evolutionary patterns and expression dynamics ofThe online version contains supplementary material available at 10.1007/s13205-022-03246-8.

Key message: Thioredoxin h-type isoforms are tissue-specific, differentially expressed in germinating seeds and under salinity stress and highly regulated by H2O2, suggestive of a role in germination and salinity adaptation in durum wheat through redox regulation. Thioredoxins (Trxs) are protein-disulfide reductases that perform multiple functions related to cellular redox homoeostasis. The most complex cluster in the family of plant Trxs is formed by h-type Trxs since their identity and functions are still largely unknown. Here, h-type Trxs from durum wheat (Triticum turgidum ssp. durum) (stated TdTrxh1, TdTrxh2, TdTrxh3, and TdTrxh9) were identified and characterized in response to oxidative stress either generated naturally (germination) or induced by salinity and hydrogen peroxide (H2O2). In silico expression analysis, based on RNA-seq data, revealed a tissue-specific expression for TdTrxh genes. Real-time q-PCR analysis showed differential expression patterns for TdTrxh genes between and within seed tissues during germination and a marked induction of TdTrxh2 and h3 ones. Moreover, the four TdTrxh isoforms were found to be differentially modulated by salinity in two durum wheat varieties contrasting in their salinity tolerance. Particularly, an upregulation of the four TdTrxh genes (mainly TdTrxh2 and h3) was noted in root tissues of the tolerant variety, while they were markedly downregulated in those of the sensitive one. This upregulation of TdTrxh genes in the tolerant variety coincided with an accumulation of H2O2 in root tissues. When exogenously applied, H2O2 increased mRNA transcripts of all TdTrxh genes in both varieties regardless of their salinity-tolerance degree. Collectively, our data suggest a non-redundant function for h-type Trxs besides to be potentially involved in salinity tolerance in durum wheat through redox regulation.

Thioredoxins (Trxs) are implicated in plant development and stress tolerance through redox regulation of target proteins. Trxs of Type h (Trxhs) constitute the largest and the most complicated cluster in the Trx family because of their unknown individual functions. Here, we identified and characterized the Phaseolus vulgaris Trxh family during development, mutualistic interactions and in response to abiotic stress. P. vulgaris (common bean) Trxh gene family (PvTrxh) encompasses 12 isoforms (PvTrxh1-h12), subdivided into 3 groups according to their amino acid sequence features. In silico RNA-seq -based expression analysis showed a differential expression of PvTrxh genes during development. RT-qPCR analysis of PvTrxh genes during nodule organogenesis revealed their highest expression in the nodule primordium (NP). Interestingly, in response to symbiosis, specific PvTrxh isoforms (PvTrxh3 and h5) were found to be highly upregulated compared to mock-inoculated plants. In addition, their expression patterns in the NP positively correlated with the symbiotic N

An efficient in vitro regeneration system using epicotyl segments was developed and then used for optimizing genetic transformation of the Tunisian 'Maltese half-blood' (Citrus sinensis) variety using phosphinothricin (PPT) resistance as a selectable marker. The maximum regeneration efficiency was achieved after incubating epicotyl explants (excised in an oblique manner) in MT culture media containing BAP (4 mg/l) and IAA (0.3 mg/l) hormonal combination in the dark for 3 weeks before their transfer to light. Data from the genetic transformation assays indicated that the highest number of regenerated-transformants was reached when the selection phase was conducted in MT culture media containing PPT (0.25 mg/l) and Carbenicillin (500 mg/l) for 3 weeks in the dark followed by 8 weeks of light. After that, transformed buds were maintained for eight additional weeks in the same culture media but with reduced PPT concentration (0.125 mg/l) before decreasing Carbenicillin dose (250 mg/l) at the second half of this last incubation period which allowed both a good shoot proliferation and an optimal rooting efficiency. Based on molecular analyses, the transgenicity of 21.42% of the regenerated vitroplants was confirmed. The developed regeneration and transformation procedures of the elite ‘Maltese half-blood’ variety can be used for orchard renewal as well as for functional studies and genome editing purposes to develop new cultivars with the desired genetic traits.

Manipulation of natural host-defense responses is a safe alternative strategy to chemicals in controlling plant diseases. Various natural compounds, including those derived from microbes, algae, and plants, as well as organic ones, such as biochar and vitamins, have been reported to protect plants from invaders through inducing a priming state leading to enhanced resistance against subsequent pathogen infection. This process, termed induced resistance (IR), involves various molecular and cellular events occurring either before (elicitation) or after (priming) pathogen infection, including the induction of reactive oxygen species (ROS), pathogenesis-related (PR) protein expression, phytoalexin production, cell wall strengthening, and callose deposition. The induction of these changes was found to be regulated by an efficient and complex signal transduction network involving mainly salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). JA and SA are the main regulators of NPR1 (nonexpressor of pathogenesis-related protein 1) transcription factor that is responsible for the induction of PR gene expression. This chapter reports the current knowledge on IR by natural compounds focusing on the molecular and cellular mechanisms underpinning their activities.

Drought stress is one of the most prevalent environmental factors limiting faba bean (Vicia faba L.) crop productivity. β-aminobutyric acid (BABA) is a non-protein amino acid that may be involved in the regulation of plant adaptation to drought stress. The effect of exogenous BABA application on physiological, biochemical and molecular responses of faba bean plants grown under 18% PEG-induced drought stress were investigated. The results showed that the application of 1 mM of BABA improved the drought tolerance of faba bean. The application of BABA increased the leaf relative water content, leaf photosynthesis rate (A), transpiration rate (E), and stomatal conductance (gs), thereby decreased the water use efficiency. Furthermore, exogenous application of BABA decreased production of hydrogen peroxide (H(2)O(2)), malondialdehyde and electrolyte leakage levels, leading to less cell membrane damage due to oxidative stress. Regarding osmoprotectants, BABA application enhanced the accumulation of proline, and soluble sugars, which could improve the osmotic adjustment ability of faba bean under drought challenge. Interestingly, mended antioxidant enzyme activities like catalase, guaiacol peroxidase, ascorbate peroxidase and superoxide dismutase and their transcript levels may lead to counteract the damaging effects of oxidative stress and reducing the accumulation of harmful substances in BABA-treated faba bean plants. In addition, exogenous BABA significantly induced the accumulation of drought tolerance-related genes like VfMYB, VfDHN, VfLEA, VfERF, VfNCED, VfWRKY, VfHSP and VfNAC in leaves and roots, suggesting that BABA might act as a signal molecule to regulate the expression of drought tolerance-related genes.

An efficient in vitro regeneration system using epicotyl segments was developed and then used for optimizing genetic transformation of the Tunisian 'Maltese half-blood' (Citrus sinensis) variety using phosphinothricin (PPT) resistance as a selectable marker. The maximum regeneration efficiency was achieved after incubating epicotyl explants (excised in an oblique manner) in MT culture media containing BAP (4 mg/l) and IAA (0.3 mg/l) hormonal combination in the dark for 3 weeks before their transfer to light. Data from the genetic transformation assays indicated that the highest number of regenerated-transformants was reached when the selection phase was conducted in MT culture media containing PPT (0.25 mg/l) and Carbenicillin (500 mg/l) for 3 weeks in the dark followed by 8 weeks of light. After that, transformed buds were maintained for eight additional weeks in the same culture media but with reduced PPT concentration (0.125 mg/l) before decreasing Carbenicillin dose (250 mg/l) at the second half of this last incubation period which allowed both a good shoot proliferation and an optimal rooting efficiency. Based on molecular analyses, the transgenicity of 21.42% of the regenerated vitroplants was confirmed. The developed regeneration and transformation procedures of the elite ‘Maltese half-blood’ variety can be used for orchard renewal as well as for functional studies and genome editing purposes to develop new cultivars with the desired genetic traits.

Thioredoxins (Trxs) are implicated in plant development and stress tolerance through redox regulation of target proteins. Trxs of Type h (Trxhs) constitute the largest and the most complicated cluster in the Trx family because of their unknown individual functions. Here, we identified and characterized the Phaseolus vulgaris Trxh family during development, mutualistic interactions and in response to abiotic stress. P. vulgaris (common bean) Trxh gene family (PvTrxh) encompasses 12 isoforms (PvTrxh1-h12), subdivided into 3 groups according to their amino acid sequence features. In silico RNA-seq -based expression analysis showed a differential expression of PvTrxh genes during development. RT-qPCR analysis of PvTrxh genes during nodule organogenesis revealed their highest expression in the nodule primordium (NP). Interestingly, in response to symbiosis, specific PvTrxh isoforms (PvTrxh3 and h5) were found to be highly upregulated compared to mock-inoculated plants. In addition, their expression patterns in the NP positively correlated with the symbiotic N2-fixing efficiency of the Rhizobium strain, as revealed by a number of symbiotic efficiency parameters (ARA, leghemoglobin content, biomass, and total soluble proteins), concomitantly with increased amounts of hydrogen peroxide (H2O2). On the other hand, distinctive PvTrxh isoforms were found to be upregulated in plant leaves, where H2O2 amounts were elevated, in response to both salt and drought constraints. When exogenously applied, H2O2 upregulated specific PvTrxh isoforms in plant leaves and roots. These findings point to a specific, rather than redundant, function for Trxh proteins in common bean beside the association of distinctive Trxh isoforms with symbiosis and abiotic stress response.

A total of 41 endophytic bacterial strains were assessed for antimicrobial activity against indicator organisms in a preliminary screening. Of these, two bacterial strains that showed a strong antimicrobial activity were selected and identified as Bacillus subtilis (Bs1 and Bs2). The activities of Bs1 and Bs2 strains and different bile acids were assessed against Botrytis cinerea and Plasmopara viticola grapevine pathogens using in vitro and in vivo methods. Bs1 and Bs2 strains strongly inhibited Botrytis cinerea growth in vitro. The cell-free filtrates of both strains also reduced Botrytis cinerea growth. Chenodeoxycholic acid (CDCA) inhibited Botrytis cinerea growth in potato dextrose agar medium and suppressed P. viticola development in grapevine leaf discs. Epifluorescence microscopy observations revealed an important restriction of P. viticola development at the vesicle stage. In addition, CDCA markedly reduced the ability of P. viticola sporangia to release zoospores in vitro, confirming the direct ...

In this work, phenolic composition, antioxidant and antibacterial activities of selected Tunisian barley varieties were studied. Swihli barley exhibited the highest total phenolic content and the strongest antioxidant and antibacterial activities. Liquid chromatography/mass spectrometry analysis revealed significant qualitative and quantitative differences in phenolic composition among the different varieties. Procyanidin B3 and catechin were the most abundant. Pearson’s correlation test revealed significant correlations between the antioxidant activities of barley extracts and both hydroferuloyl glucose and catechin-3-glucose.

International audience; Recently, thiamine (VitaminB1) has been shown to induce resistance against Pseudomonas syringae in Arabidopsis plants through priming of defense responses. In this paper, we have demonstrated the efficiency of thiamine to induce resistance against downy mildew caused by the oomycete Plasmopara viticola in a susceptible Vitis vinifera cultivar "Chardonnay" under glasshouse controlled conditions by providing a dual mode of action involving direct antifungal activity and elicitation of host-defense responses. Thiamine-induced defense responses included the generation of hydrogen peroxide (H(2)O(2)) in both grapevine suspension cultured cells (SCC) and plant leaves, upregulation of an array of defense-related genes and the induction of other defense responses at subcellular level such as callose deposition in stomata cells, phenolic compounds accumulation and hypersensitive response (HR) like-cell death. Epifluorescence microscopy studies revealed dramatic changes in P. viticola individual developmental stages during its colonization of the intercellular space of the leaf mesophyll in thiamine-treated plants. Collectively, our report evidenced the efficiency of thiamine in the control of downy mildew in grapevine by direct and indirect effects, suggesting that thiamine could be an attractive alternative to chemical fungicides in disease management in vineyards.

International audience; Methionine (Met) is a nutritionally essential sulfur-containing amino acid (SAA) known for its preponderant role as initiator in protein synthesis. However, other functions for Met in plants are not well described. The implication of this SAA in oxidative stress tolerance has been recently reported, however the mode of action of Met is still poorly understood. Here, we analyzed the elicitor activity of Met in grapevine as well as its effect on Plasmopara viticola resistance. The results show that Met induces hydrogen peroxide (H2O2) generation, a key element in plant defense signaling, and upregulates the expression of a battery of defense-related genes. Transcript levels of these genes were not further modulated by P. viticola inoculation of Met-pretreated plants, suggesting an elicitor role rather than a priming role for Met in grapevine. Met treatment also reduces P. viticola development in grapevine plants grown under glasshouse controlled-conditions. Fungitoxicity assays revealed that Met possesses a moderate antifungal activity compared with cysteine (Cys), another SAA known for its toxic effect to a large spectrum of fungi.

In order to reduce the impact of nitrogen pollution and to increase the agronomic value of plant wastes to be reused as organic fertilizer, we have investigated the removal of ammonium from aqueous solutions onto cactus leave fibers (CLF), and the mechanisms involved in the retention of ammonium at CLF surface. The results showed that ammonium retention onto these fibers occurred for a wide pH (6–10) and temperature ranges (20–60 °C) and the biosorption potential of CLF increased with temperature from 1.4 to 2.3 mg g −1 for initial concentration of 50 mg L −1 . The modeling studies showed that the ammonium biosorption was well described by the pseudo-second-order model, predicting therefore, chemisorption interactions-type at earlier stages and by intraparticle diffusion at later stages. Biosorption is governed by film diffusion process at higher concentrations and by particle diffusion process at higher temperatures. The surface of CLF determined by SEM revealed the presence of cracks and cavities which may allow the intraparticle diffusion and the ion exchange processes. Moreover, FTIR and EDX analysis before and after ammonium retention showed that the main mechanisms involved in the removal of ammonium were the ionic exchange by calcium ions as well as H + and the complexation with carboxylic, alcoholic and phenolic groups.