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Arabinogalactan proteins (AGPs) are extracellular glycoproteins released into the conditioned medium (CM) of cultured cells and reported here as a novel family of plant promoting factors that trigger an increase of cell growth in grapevine embryogenic suspensions. Yariv reagent that binds to AGPs disrupted their biological function resulting in a significant decrease of callus fresh weight. Differential accumulation of AGPs among grape varieties were surveyed by Yariv-based precipitation and immunoblot detection. Cell suspenion-derived CM of two contrasting varieties (Tempranillo and Riesling) in terms of growth rate in cell culture displayed specific protein patterns. Western blot demonstrated the presence of a chitinase responsible to decompose AGPs into lipochito-oligosaccharides indicating that Tempranillo pro-embryogenic masses secreted more chitinase than Riesling cell line making them more proliferative. AGP and chitinase abundance resulted in increased growth with maintenance of somatic embryogenesis potential while removal of these extracellular proteins by frequent subculture disrupted embryogenic cell proliferation and activated regeneration. AGPs were also shown to enhance the Agrobacterium-mediated transformation of embryogenic material as revealed by an improved transient GFP expression efficiency that can reach 200%. Data imply that AGPs are highly involved in the bacterial binding to the host cell surface helping the transfection process. This study suggests that AGPs have a key role in maintenance of embryogenic competence, boosting cell growth and improving transient gene transfer. These findings give new insights towards AGP endorsement for use as a novel plant promoting factor in cell tissue culture with downstream applications in crop improvement and gene transfer manipulations. Key message: AGPs enhance cell growth in grapevine embryogenic suspensions, induce maintenanceand proliferation of pro-embryogenic masses, inhibit embryo maturation and improve Agrobacterium-mediated transformation. Yariv reagent inhibits growth through disrupting AGP function. [ABSTRACT FROM AUTHOR]

Using reliable salt tolerance markers is a key component in barley breeding programs. In this study, physiological and antioxidative markers of two Tunisian barley salinity tolerance contrasting genotypes Boulifa (B) and Manzel Habib (MH) were assessed at 0, 3, 6 and 9 days of 200 mM salt treatment. Salinity caused decrease in growth, degraded photosynthetic activity and reduced water-holding capacity in both genotypes with more pronounced negative effects in the salt-sensitive (MH) compared to the salt-tolerant (B) genotype. On the other hand, the lower oxidative damage in B compared to MH under salt stress could be explained by higher activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione peroxidase (GPX) and glutathione reductase (GR). Additionally, a genotype-specific pattern of enzyme activity and corresponding gene expression was revealed in the two barleys under salt stress. In this context, a positive correlation was noted for the SOD. On the other hand, multivariate analysis marked SOD and APX as the most discriminating factors between both stressed genotypes. Our findings could be considered for selection in breeding programs for salt stress tolerance in barley. [ABSTRACT FROM AUTHOR]

Salt stress tolerance is a complex trait reducing drastically barley production. The present study assessed variability among two salt-tolerant contrasting barley genotypes on ROS-scavenging enzymes, osmorptectants, growth, water status and photosynthetic activity. The screening was released at the early vegetative stage under 200 mM NaCl during 0, 2 and 9 days. The results showed a significant earlier and higher increase in enzyme activities and transcript abundances of SOD and APX, in the salt-tolerant compared to the salt-sensitive genotype, In addition, the salt-tolerant barley genotype had better osmoprotection ability with higher accumulation of proline and soluble sugars contents. Hence conferring a differential growth performance among barley salt stress contrasting genotypes. Furthermore, High positive significant correlations have been detected between the antioxidative response (assessed by antioxidant enzymes activities and the expression profiles of their respective genes) and the osmotic response (evaluated by both proline and soluble sugars contents) under salt stress. Hence emphasizing the involvement of oxidative and osmotic homeostasis adjustment on averting ROS accumulation and resulting in significant growth rate sustain, water use efficiency and photosynthetic potential maintenance under salt stress. [ABSTRACT FROM AUTHOR]

Phytase activity, phosphorus and phytate contents in hydroponic fodder (up to 12 days of grain germination) of four Tunisian barley (Hordeum vulgare L.) cultivars (Arbi, Ardhaoui, Souihli, and Rihane) were studied. Barley cultivars differed significantly in their phytase activity (0.6–1.6 U/g), phosphorus (3.2–5.0 mg/g DM) and phytate (4.2–4.7 mg/g DM) contents. Phytase increased significantly up to 8 days of germination and decreased steadily thereafter. The phytase activity after 8 days of germination was increased up to tenfold in Arbi and Ardhaoui cultivars, eightfold in Souihli and fivefold in Rihane. The increase in phytase activity during germination was accompanied by a significant decrease in phytate content for all barley cultivars (reduced by 92–97%). The decrease in phytate content of sprouted barley by germination should improve phosphorus availability of the grain. Based on their phytase activity and phosphorus contents before germination, barley cultivars are ranked as Rihane > Ardhaoui > Souihli > Arbi. However, after germinating for 12 days the differences among varieties in phytase activity, phytate and phosphorus contents became non-significant. Further research is warranted to highlight the effect of germination on other nutritional attributes of hydroponic sprouted barley and its suitability as a feedstuff for farm animals. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

When constrained by in vitro culture conditions, microspores from Opuntia ficus-indica (L.) Mill. (Barbary fig) anthers were forced to stall out their gametophytic pathway and switch towards androgenesis. Five microspore stages were characterized based on cellular architecture. A relationship was also established between anthers and bud flower features. Anthers were cultured on three culture media containing 2,4-dichlorophenoxyacetic acid, thidiazuron and gibberellic acid at 22°C for 4 wk, followed by heat shock treatment at 32°C or 42°C for 2 wk, and the stressed material was recultured at 22°C for 24 wk in the dark. When anthers were heat shocked at 32°C and 42°C, the cultivated anthers swelled and burst, followed by the microspores flowing onto the explant surface. Androgenesis occurred directly and indirectly at uni- and binucleate stages. The micromorphology of multicellular, proembryos, globular, torpedo and cotyledonary-like-shaped structures from dehisced anthers was confirmed by environmental scanning electron microscopy. Furthermore, at 42°C, microscopic analysis demonstrated that the non-responsive microspores achieved pollen maturation and more rarely, the emission of a pollen tube. However, 11.4 to 14.4% of the mature pollen grains were converted into pollen embryos. The established system may serve, for the first time, as a protocol to produce microspore embryos in O. ficus-indica. Nevertheless, more efforts are needed to complete the development of diplo-haploid plantlets. [ABSTRACT FROM AUTHOR]

Salinity is one of the most important abiotic stresses, especially in arid regions. Such devastating constraint is converted mainly to oxidative burst. Thus, plants have to develop strategies to scavenge salt-related regenerated oxidant molecules. In the present work, fully aged plants derived from two Vitis vinifera L. cultivars, the Tunisian autochthonous tolerant genotype Razegui and the salt sensitive Syrah, were analyzed regarding their short term response to 100 mM NaCl, in hydroponic cultures. The ratio [ASA/ASA + DHA] was calculated on the basis of the oxidation of ascorbic acid (ASA) into dehydroascorbic acid (DHA) in leaves. Results proved that oxidative stress was generated. This led to the accumulation of malondialdehyde which referred to a lipid peroxidation mainly in the sensitive Syrah. In order to cope with these oxidative disturbances, trans-resveratrol as well as its glucosides trans-piceid and cis-piceid have been de novo synthesized in the sensitive variety. Razegui stilbene concentrations were presented here for the first time and unexpectedly did not show a very important variation during the salt elicitation. [ABSTRACT FROM AUTHOR]

To better understand micromorphological and structural changes, histological sections provide additional insight into cellular process and developmental pathways occurring in oat somatic embryogenesis. Environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM) were also used to follow the ultrastructural modifications during this system. Histological observations allowed following the events leading to the development of mature somatic embryos. The scheme includes the following steps: cell reactivation, the first organized cell division in diads, triads, tetrads as well as octant stages, the observation of an extracellular matrix (ECM) as a fibrillar material that bounded the surface of individualized proembryos. The transition from proembryo stage to an early globular somatic embryo was noted, where the embryogenic cortex is surrounded by the protoderm. The late globular stage was marked by bipolarity. The early and late transitional stages, the coleoptilar, mature and germinated stages were also described. The ESEM allowed us to follow some rearrangements, related to the morphology and surfaces involved in somatic embryos development. These events are proembryo formation, transition from proembryo to globular stage, marked by protoderm formation, scutellum and coleoptile development and finally somatic embryos germination. The TEM showed that embryogenic cells were very rich in organelles; mitochondria, rough endoplasmic reticulum, Golgi apparatus and ribosomes. Cells of proembryos, globular and late somatic embryos showed more vacuoles and differentiated organelles. The ECM was also detected by TEM as fibrillar material coating the cell walls. These results on structural and ultrastructural changes provided new insights and findings on oat somatic embryogenesis. [ABSTRACT FROM AUTHOR]

Hybridity and the genuineness of hybrids are prominent characteristics for quality control of seeds and thereby for varietal improvement. In the current study, the cross between two local barley genotypes (Ardhaoui: female; Testour: male) previously identified as susceptible/tolerant to salt stress in Tunisia was achieved. The hybrid genetic purity of the generated F putative hybrids and the fingerprinting of the parents along with their offspring were assessed using a set of 17 nuclear SSR markers. Among the analyzed loci, 11 nSSR were shown polymorphic among the parents and their offspring. Based on the applied 11 polymorphic SSR loci, a total of 28 alleles were detected with an average of 2.54 alleles per locus. The locus HVM33 presented the highest number of alleles. The highest polymorphism information content value was detected for the locus HVM33 (0.6713) whereas the lowest PIC value (0.368) was revealed by the loci BMAC0156, EBMAC0970 and BMAG0013 with a mean value of 0.4619. The probabilities of identical genotypes PI for the 11 microsatellite markers were 8.63 × 10. Banding patterns among parents and hybrids showed polymorphic fragments. The 11 SSR loci had produced unique fingerprints for each analyzed genotype and segregate between the two parental lines and their four hybrids. Parentage analysis confirms the hybrid purity of the four analyzed genotypes. Six Tunisian barley accessions were used as an outgroup in the multivariate analysis to confirm the efficiency of the employed 11 nSSR markers in genetic differentiation among various barley germplasms. Thus, neighbor joining and factorial analysis revealed clearly the discrimination among the parental lines, the four hybrids and the outgroup accessions. Out of the detected polymorphic 11 nuclear SSR markers, a set of five markers ( HVM33, WMC1E8, BMAC0154, BMAC0040 and BMAG0007) were shown to be sufficient and informative enough to discriminate among the six genotypes representing the two parental lines and the four hybrids from each others. These five nSSR markers presented the highest number of alleles per locus ( A), expected heterozygosity ( H), PIC values and the lowest probabilities of identity (PI). These nSSR loci may be used as referral SSR markers for unambiguous discrimination and genetic purity assessment in barley breeding programs. [ABSTRACT FROM AUTHOR]

Salinity problems for vineyards are in concerns, especially in coastal areas where several aquifers are reported to be affected by seawater intrusion and agricultural contamination. Saline irrigation affects growth, yield, and fruit quality of grapevines. Exploring germplasm base through wild ancestors of the target species is a novel adopted strategy to increase crop tolerance to irrigation with saline water. The effects of salt on growth, organic and inorganic solute accumulations, and chlorophyll florescence were studied on 3-month-old plants of six Tunisian wild grapevines with the objective to identify salt tolerance mechanisms and select tolerant genotypes. Potted plants were grown under controlled conditions and irrigated for 14 days with 0, 100, and 150 mM NaCl nutrient solution. Parameters analyzed were related to growth, water relations, mineral nutrition, and chlorophyll fluorescence. Several processes are operating either at the whole plant or at cell level. They appear to be involved in salt tolerance of wild grapevines and are more efficient in tolerant accessions. Salt adversely affects plant growth and plant nutrition. Reductions of shoot growth rate (relative growth rate, day) reached 49% of control since 100 mM NaCl. They were assigned to stomatal closure and alteration of potassium nutrition and photochemistry. There were significant differences ( P < 0.05) within accessions, Tebaba was the most tolerant and Houamdia the most sensitive, while the others were intermediate. [ABSTRACT FROM AUTHOR]

The expression of a gene originally identified by means of a salt-stress-associated partial cDNA showing a genotype-dependent response, was studied upon exposure to salt and drought stress and during seed development of grapevines. The complete open reading frame has been cloned and the corresponding untranslated regions have been characterized by 5′- and 3′-RACE leading to a refinement and correction of the predicted gene model in the recent 12× Vitis genome assembly. The open reading frame of the single copy gene designated Vv- α- gal/SIP encodes for a polypeptide of 774 amino acids with a calculated molecular mass of 84.9 kDa. Protein sequence comparisons suggest that the gene belongs to a growing family of plant-specific alkaline α-galactosidases. 5′-RACE identified a not yet documented transcript species derived from the same gene locus, which does not lead to the formation of a full-length transcript. The 'aberrant' transcript harbours an alternative 5′-UTR and originates from an internal transcriptional start site 1.4 kb downstream of the predominant transcriptional start site. Levels of transcripts containing the different 5′-UTRs were compared under salt stress conditions. [ABSTRACT FROM AUTHOR]

The physiological and molecular response to salt stress was studied in two wild grapevine ( Vitis vinifera L . ssp. sylvestris or Vitis sylvestris) accessions 'Khédhayria' and 'Houamdia', previously identified as salt-tolerant and salt-sensitive pair wise. Plants from both accessions were subjected to a progressive salt stress by the use of a nutritional solution containing up to 150 mM NaCl for 2 weeks. Salt stress adversely affected growth and water potential since the first day of exposure to 150 mM NaCl. However, chlorophyll fluorescence parameters were unchanged until 14 days of salt exposure. At that time point the predawn water potential (Ψ), the non-photochemical quenching of fluorescence (NPQ) and the coefficient of photochemical quenching (q) were significantly less altered in the tolerant accession. At the molecular level semi-quantitative RT-PCR assays revealed a differential expression of ( Vs α- gal/SIP and Vs DHN) genes within these contrasting accessions after exposure to 24 h and 14 days of salt. Comparably, the Vs RD22 gene had increased slightly after only 14 days of treatment in both accessions. These results were the first pieces of information reported on the early and late regulation of salt response genes in wild grapevines. Furthermore, genotype-dependent parameters such as NPQ, q, mRNA levels of Vs α-gal/ SIP and Vs DHN could be used to screen salt-tolerant wild grapevine genotypes. [ABSTRACT FROM AUTHOR]

The regeneration ability of a Tunisian barley accession originated from Kerkena islands was monitored through somatic embryogenesis and organogenesis. To prevent or to reduce normal germination, longitudinally bisected as well as base-wounded mature caryopses were cultured on a modified Chée and Pool-based medium (CP) enriched with different phytohormonal combinations. The greatest embryogenesis response was obtained when base-wounded caryopses were cultured on CP enriched with 2 mg/l chlorophenoxyacetic acid + 2.5 mg/l kinetin (76.85%). The same combination coupled to longitudinally bisected caryopses led to the embryogenic induction at the hypocotyl base of the germinated caryopses (61.9%). Embryogenic calluses differentiated into globular, heart-shaped, torpedo, and fully differentiated stages of somatic embryos on hormone-free Murashige and Skoog-based medium. Rooted plantlets were successfully transferred to soil and grown to maturity in the greenhouse and produced fertile seeds within 3 mo. On the other hand, organogenesis was achieved on CP enriched with 2 mg/l 2,4-dichlorophenoxyacetic acid + 2.5 mg/l kinetin. Histological aspects and scanning electron microscopy of both regeneration methods confirmed further the embryogenic and organogenic nature of the established processes. This efficient plant regeneration system provides a foundation for generating transgenic plants and germplasm preservation of 'Kerkena' barley accession. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the inhibitory effect of ethanol and aqueous extracts from a stem of Opuntia ficus indica on replication of three kinds of viruses: two enveloped viruses [herpes simplex virus type 2 (HSV-2), influenza A virus (IFV-A)], and one non-enveloped virus [poliovirus type 1 (PV-1)]. Only ethanol extract from the cactus stem showed significant antiviral activity in vitro. Two chlorophyll derivatives, pheophorbide a and pyropheophorbide a, were isolated as active substances exhibiting potent virucidal effects on HSV-2 and IFV-A, but no activity against PV-1 was observed. These findings suggest that these active compounds might recognize specific glycoproteins of enveloped viruses, precluding their binding to host cell receptors and inhibiting viral infections. [ABSTRACT FROM AUTHOR]

Proteomic and transcriptomic analyses of pathogenesis-related proteins, PR10, were carried out by subjecting adult plants of the salt-tolerant grapevine cv. Razegui to 100 mM NaCl for 6 and 24 h under controlled greenhouse conditions. Within 6 h of salt exposure, an increase in levels of RzPR10 was observed in the roots. PR10 mRNA levels in leaves were significantly different than those in roots; moreover, significant differences for mRNA levels were found between treated and control plants. Within 24 h of salt treatment, roots exhibited the highest levels of RzPR10 protein, but no differences were observed for mRNA levels in both leaves and roots. Overexpression of Vvpr10 cDNA, under the control of the Gal promoter, in the yeast Saccharomyces cerevisiae revealed that growth of transformed cells on a minimal medium containing 500 mM NaCl is similar to that of cells cultivated on NaCl-free medium. This indicated that Vvpr10 gene was functional in yeast and conferred tolerance to high salt concentrations. [ABSTRACT FROM AUTHOR]

The genetic diversity among 126 exotic (108) andreference array (RA) melon ( Cucumismelo L.) accessions (18) was assessed byvariation at 49 random amplified polymorphic DNA marker bands(putative loci) using 29 10-mer primers. Africanaccessions of unknown melon market classes were compared to the RAaccessions from a broad range of C. melo subsp. melo groups(Cantalupensis, Conomon, Inodorus and Flexuosus). Althoughdifferences in groupings occurred after multidimensional scaling andcluster analysis, both analyses placed African accessions into twogroups, which were separate from RA groupings. One African group of33 accessions containing accessions from Zimbabwe (5),Zambia (24), Mali (1), one of two Senegalaccessions and two of three South African accessions examined. Thesecond group, which consisted of 67 accessions containing collectionsfrom Egypt (40), Tunisia (6), Libya(13), Morocco (1), Algeria (2),Ethiopia (1), Niger (1), Sierra Leone(1), S. Africa (1), Zambia (1) andZimbabwe (1). Depending on the multivariate analysistechnique employed, accessions from Kenya, Senegal and Ghana formedeither unique groupings or were grouped with accessions(Cantalupensis) from the RA. Both analyses indicate thatthe genetic differences inherent between the African gene pools isassociated with the geographic proximity of African countries(northern vs. central-southern Africa) in thegermplasm array examined. Moreover, these data indicate that thegenetic diversity of U.S. and European commercial RA germplasm(Cantalupensis and Inodorus) could be enhanced by theintroduction of genetic variation from African accessions, and thatit would be advantageous to acquire more accessions from thisgeographically and ecologically varied region to ensure the retentionof existing genetic diversity. [ABSTRACT FROM AUTHOR]