Organic acid (OA) metabolisms are of fundamental importance but very limited data are available on the responses of plant OA metabolisms to Mg-deficiency. Seedlings of Citrus sinensis (L.) Osbeck cv. Xuegan were irrigated with Mg-deficient (0, 50, or 500 μM MgSO₄) or Mg-sufficient (2000 μM MgSO₄) nutrient solution every other day for 12 weeks. Thereafter, we investigated the content of Mg, malate, and citrate as well as the activities of acidmetabolizing enzymes in roots and leaves. Root malate content remained stable except for an increase in the highest Mg content and root citrate content increased with increasing root Mg content. As leaf Mg content increased, leaf malate and malate + citrate content decreased whereas leaf citrate content increased. Mg-deficiency decreased or did not affect activities of citrate synthase (CS), aconitase (ACO), phosphoenolpyruvate carboxylase (PEPC), NADP-isocitrate dehydrogenase (NADP-IDH), NAD-malate dehydrogenase (NAD-MDH), NADP-malic enzyme (NADP-ME), and pyruvate kinase (PK) in roots, whereas phosphoenolpyruvate phosphatase (PEPP) activity slightly increased. In contrast, Mg-deficient leaves had higher or similar activities of enzymes above mentioned except PEPP, NAD-MDH, and NADP-ME. In conclusion, both glycolysis and tricarboxylic acid (TCA) cycle may be up-regulated in Mg-deficient leaves but down-regulated in Mg-deficient roots.

Cadmium is a widely spread pollutant and the objective of this study was to study the effects of different concentrations of Cd (0, 50, and 100 μM) on the soybean seedlings treated for 10 d. The growth was inhibited and chlorophyll content, net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, probability that a trapped exciton moves an electron into the electron transport chain beyond QA - (ET_O/TR_O), performance indexes (PI_ABS), and amount of active reaction centres per excited cross section (RC/CS_O) were decreased with the increasing Cd concentration. The leaf reflectance increased in visual range (500-670 nm) and decreased in near-infrared range (750-1 000 nm). The accumulation of Cd in the roots was much higher than that in the stems and leaves.

To examine whether ferulic acid (FA) could protect plants from dehydration stress and to investigate a mechanism for the protection, cucumber seedlings were pretreated with 0.5 mM FA for 2 d and then were exposed to dehydration induced by 10 % polyethylene glycol 6000. After pretreatment with FA, the activities of antioxidant enzymes (catalase, superoxide dismutase, and quaiacol peroxidase) in leaves were higher than under dehydration treatment alone which was in accordance with the increased transcript levels of respective genes. Moreover, the combination of FA pretreatment and dehydration reduced the content of superoxide radical, hydrogen peroxide, and malondialdehyde, and increased the relative water content and content of FA, proline, and soluble sugars in comparison with dehydration alone. We propose that pretreatment with FA protects cucumbers against dehydration stress by decrease of lipid peroxidation due to activation of antioxidant enzymes and by increase of proline and soluble sugar content in leaves.

In different plant species, vanadium has been considered either as beneficial or as a toxic element, or even as secondary metabolism elicitor, but the mechanisms involved are still not completely understood. In this study, the responses of Phaseolus vulgaris L. cv. Contender roots and leaves to different vanadyl sulfate concentrations were studied. The plants grown hydroponically with V had thicker roots, a less developed main root, and a smaller number of secondary roots than the control plants. The V content in roots and leaves was correlated with V supply concentration but the V content in leaf was always much lower than in the root, which leads us to conclusion that V accumulates in the roots and only small quantities are transferred to the leaves. However, thylakoid disorganisation was observed in the chloroplasts of plants grown with vanadyl sulphate.

It is widely accepted that fruit abscission is a highly regulated developmental process that is both influenced and activated in response to changing environment and plays crucial roles in the health and reproductive success of plants. Recent evidences showed that numerous genes related to metabolic and signalling pathways were coordinately implicated in regulating fruit abscission. Cross talks within hormones, between saccharides and hormones, as well as between polyamines and ethylene result in synergetic or antagonistic interactions which together play an important role in adjusting fruit abscission. Although hormones are the most studied internal factors related to abscission, the role of saccharides and polyamines during fruit abscission is emerging now. The characterizations of the molecular mechanisms of regulating fruit abscission are essential to develop effective strategies for controlling this process in plants.

Diploid wheat Triticum monococcum L. is a model plant for wheat functional genomics. Chlorophyll-deficient mutant (clm1) was identified during manual screening of the ethyl methanesulphonate (EMS)-treated M₂ progenies of T. monococcum accession pau14087 in the field. The clm1 mutant, due to significantly decreased chlorophyll content compared with the wild-type (WT), exhibited pale yellow leaves which slowly recovered to green before flowering. The clm1 mutant showed early flowering, reduced number of tillers, trichome length and density, and different shape as compared with the WT. At the same time, clm1 mutant culm had more chlorophyll-containing parenchymatous tissues compared to WT, presumably to absorb more sunlight for photosynthesis. Genetic analysis indicated that the clm1 mutation was monogenic recessive. The clm1 mutant was mapped between Xgwm473 and Xwmc96 SSR markers, with genetic distances of 2.1 and 2.6 cM, respectively, on the 7A^mL chromosome.

Microsatellite markers were developed for Dicksonia sellowiana (Dicksoniaceae), an overexploited and endangered tree-fern species native to Brazil. From an enriched genomic library, 11 primer pairs were selected and used to characterize 36 D. sellowiana individuals from six Brazilian populations. Eight primer pairs amplified dinucleotide and hexanucleotide repeats with two to ten alleles per locus; three primer pairs were monomorphic. For the set of polymorphic markers, the mean observed and expected heterozygosity ranged from 0.29 to 0.44 and from 0.27 to 0.56, respectively. Eight of the primer pairs were also successfully amplified for Cyathea vestita (Cyatheaceae). These molecular markers can be useful tools for genetic studies aiming to analyze the impact of deforestation and overexploitation on the population structure and genetic diversity of fern species from various botanical families.

Three wheat and two barley populations were studied in order to find loci responsible for dormancy and pre-harvest sprouting. A classical quantitative trait loci analysis was combined with an association mapping approach. Many quantitative trait loci and marker trait associations could be detected on all seven chromosome groups of wheat and on the chromosomes 2H, 3H, 5H, 6H, and 7H of barley. Especially, the known regions on chromosomes 3A and 4A for wheat and 5H for barley were confirmed. Putative functions could be found via a candidate homologues search and via expressed sequence tag annotation. On chromosome 3A, the viviparous1 gene is located which is associated to preharvest sprouting and dormancy. On chromosome 4A, a protein is detected which belongs to the aquaporin family. In barley, an association with the aleurain gene on chromosome 5H was found. The expression of aleurain is regulated by abscisic acid and gibberelic acid. An influence of both hormones on dormancy and pre-harvest sprouting is known. It can be concluded that dormancy and pre-harvest sprouting are very complex traits regulated by multigenes and/or quantitative trait loci.

We applied the alkaline version of the single-cell gel electrophoresis (comet assay) to seedlings of heterozygous tobacco (Nicotiana tabacum L. var. xanthi) treated with zinc acetate dihydrate (20 to 80 mM Zn²⁺ for 2 h or 2 to 12 mM Zn²⁺ for 24 h). A dose dependent increase in DNA damage expressed by the tail moment values were observed in nuclei isolated from the roots after 2 and 24 h Zn²⁺ treatments. In contrast, Zn²⁺ did not induce significant DNA damage to leaf nuclei, with the exception of 10 or 12 mM Zn²⁺ for 24 h. Somatic mutations, identified as dark green, yellow, and dark green/yellow double sectors on the pale green tobacco leaves were not detected after any Zn²⁺ treatments. The accumulation of Zn in roots and shoots was determined by inductively coupled plasma optical emission spectrometry and the Zn content in roots was about three times higher than in shoots.

The genetic diversity and ancestral relationships of a number of Trifolium species was revealed by using the amplified fragment length polymorphism (AFLP) and the random amplified polymorphic DNA (RAPD) markers. Both markers produced few species-specific markers. Using distance and parsimony methods, in NTSYS-pc and PAUP software programs, we clearly differentiated the accessions of white clover from other closely related progenitors. The phylogenetic trees, produced by PAUP, also reinforced the close affinity of T. nigrescens and the allopolyploid white clover in support of former views that this diploid species could have been the donor of one of two genomes of the allotetraploid T. repens. In addition, the dendrograms, produced by NTSYS-pc, also indicated close affinity of T. nigrescens and T. occidentale to the accessions of T. repens. These data is congruent with karyological and phylogenetic affinities between the white clover and T. occidentale. The relationships between the examined accessions, in the T. repens gene pool, may be regarded to indicate the presence of shared alleles between T. repens, T. occidentale and T. uniflorum. Further, T. occidentale showed close phylogenetic relations to T. pallescens.

To investigate a possible involvement of nitric oxide in gene regulation of glutathione and flavonoid synthesis pathways, maize seedlings were treated with sodium nitroprusside (SNP), a NO donor, and apocynin (APO), an inducer of NO production. After 12-h treatment, the transcripts of γ-glutamylcysteine synthetase (γ-ecs), glutathione synthetase (gsh-s), chalcone synthase (chs), phenylalanine ammonia lyase (pal.1), myb-related protein P (P1) and actin 1 (act) genes were quantified in maize leaves by real time PCR, using α-tubulin as standard transcript. The level of γ-ecs and gsh-s transcripts in maize leaves were increased 9-fold and 12-fold, respectively, following SNP treatment, while after APO treatment, those transcripts were not significantly different from control plants. SNP-treated maize leaves did not show significant changes in pal.1 and chs expression. NO content in maize leaves was increased in SNP and APO treated plants in comparison to control plants. In conclusion, our experiments suggested that genes involved in glutathione synthesis could be modulated by SNP in maize leaves. On the other hand, APO had no effect on γ-ecs and gshs gene expression.

During the period of senescence of desert plant Alhagi sparsifolia Shap. the maximum photochemical quantum yield measured as variable to maximum fluorescence ratio (F_v/F_m) remained relatively high, although the number of active reaction centres per cross section (RCs) decreased significantly. The efficiency of electron acceptors beyond the primary quinone acceptor (Q_A) decreased. The effect of temperature and irradiance on photosystem activity was maximum after 6 d. Our results suggest that: 1) the down-regulation of photosystem activity was due to the decline of both RCs and electron acceptance between plastoquinone (PQ) and cytochrome (cyt) b6/f; 2) photosystem activity presented negative correlation with daily mean temperature, and 3) reduction of daily sunshine period and increase of temperature at noon can stimulate the speed of senescence.

Changes in ultrastructure of meristematic cells as well as growth and lipid peroxidation in roots of 3-d-old seedlings obtained from control (C), hydroprimed (H) and hydroprimed with melatonin (H-MEL) seeds after 2 d of incubation at 25 or 5 °C and 2 d of re-warming after chilling were investigated. Under 25 °C hydropriming (H and H-MEL) inhibited root growth, but after chilling and re-warming a positive MEL effect on root elongation was observed. The results show decreased lipid peroxidation in H-MEL roots already after chilling, but the significant extent of MEL impact was seen after re-warming. Similarly at the ultrastructural level, the protective effect of MEL at chilling was also visible, especially in plastids, and this effect maintained also after re-warming.

Frost tolerance of ten Bulgarian winter wheat (Triticum aestivum L.) cultivars (Milena, Pobeda, Sadovo-1, Enola, Kristal, Laska, Svilena, Russalka, No301 and Lozen) and five foreign cultivars (Mironovskaya 808, Bezostaya-1, Rannaya-12, Skorospelka-35 and Chinese Spring) was studied in two experimental seasons following natural cold acclimation and in one experiment carried out in controlled acclimation conditions. Considerable intercultivar variability in plant survival was observed after freezing at -21 °C following sufficient cold acclimation, or at -18 °C following insufficient or controlled acclimation. In seven cultivars, the effects of chromosome 5A on frost tolerance were investigated in their F₂ hybrids with chromosome 5A monosomic lines of cultivars with high, intermediate and low frost tolerance. The effects of chromosome 5A depended on the stress severity and the genetic background of the hybrids and varied even in cultivars of similar frost tolerance and vernalization requirements. Effects of other chromosomes besides 5A on frost tolerance were assumed. The analysis of six microsatellite loci located in the interval from centromere to Vrn-1 on of chromosomes 5AL, 5BL and 5DL showed that the major loci determining frost tolerance in Bulgarian winter wheats were Fr-A2 on chromosome 5AL, and, to a lesser extent, Fr-B1 on chromosome 5BL. A strong association of the 176 bp allele at locus wmc327 tightly linked to Fr-A2 with the elevated frost tolerance of cvs. Milena, Pobeda, Sadovo-1, Mironovskaya-808 and Bezostaya-1 was revealed. Relatively weaker association between frost tolerance and the presence of the 172 bp allele at locus Xgwm639 tightly linked to Fr-B1 was also observed.

Recently, the truncated hemoglobin gene (trHb) was discovered in plant species, however, its role has not yet been determined. In this study, the gene expression of wheat trHb (TatrHb) was analyzed under various biotic and abiotic stresses. TatrHb transcript levels increased in NaCl-treated leaves and gibberellic acid (GA₃)-treated roots. In addition, sodium nitroprusside (SNP), a nitric oxide donor, induced an increase in TatrHb transcript levels in roots and leaves. A yeast two-hybrid assay (YIIH) was used to screen a hypoxia-treated wheat seedling library with the goal of determining the putative function of TatrHb. In this YIIH assay, photosynthesis-related genes that showed high homology to the Hordeum vulgare chloroplast photosystem I PSK-I subunit and Zea mays photosystem II subunit PsbS1 were detected and their interactions with TatrHb were confirmed. Subcellular localization of a TatrHb-green fluorescent protein (GFP) fusion protein and bimolecular fluorescence complementation (BiFC) assay suggested that TatrHb is involved in photosynthesis. The TatrHb-GFP fusion protein was localized in the plastids and the yellow fluorescent protein signal indicated that the TatrHb protein interacted with PSK-I and PsbS1 in the chloroplast.

Using aseptic plantlets obtained from stem node explants of hybrid red miniature rose (Rosa hybrida cv. Fairy Dance), the effects of shoot physiological status, medium ingredients, and culture thermoperiod on in vitro flowering were evaluated. Shoot height, subculture media for shoot multiplication, sucrose concentration, plant growth regulators (PGRs), mineral substances in media, and thermoperiod had a significant effect on the percentage of in vitro flowering. Shoots 3 ± 0.2 or 2 ± 0.2 cm in height cultured on Murashige and Skoog (MS) medium containing 2.0 mg dm^-3 6-benzyladenine (BA), 0.2 mg dm^-3 α-naphthaleneacetic acid (NAA), and 20 g dm^-3 sucrose were more suitable for in vitro flowering than shoots 4 ± 0.2, or 5 ± 0.2 cm in height. The most suitable sucrose concentration for in vitro flowering was 50 g dm^-3 and the most suitable PGRs were a combination of 3.0 mg dm^-3 BA and 0.1 mg dm^-3 NAA. Increasing the potassium nitrate to ammonium nitrate ratio or increasing the phosphate concentration in MS medium had a positive effect on in vitro flowering. The percentage of in vitro flowering was significantly higher at day/night temperature of 28/20 °C than at other constant temperatures. The percentage of in vitro flowering shoots reached 68.33 % despite the occurrence of abnormal flowers and some unique developmental patterns. It makes miniature rose a potentially new in vitro experimental platform for research on the molecular mechanisms of flowering ornamental plants.

Apocynin was used as an inducer of nitric oxide (NO) synthesis in leaves of two maize (Zea mays L.) cultivars (SHS 3031 and DKB 240). The transcription of γ-glutamylcysteine synthetase (γ-ecs), glutathione synthetase (gshs), chalcone synthase (chs), flavanone 3-β-hydroxylase (fht1), glutathione S-transferase (gst23), ascorbate peroxidase (apx1, apx2), catalase (cat1, cat3), and superoxide dismutase (sod2) genes were quantified in leaves of maize and NO presence was detected by fluorescence microscopy. An increase in the fluorescence after apocynin treatment was not observed in leaves of DKB 240 but leaves of SHS 3031 showed higher fluorescence after 6 and 12 h of apocynin treatment. We observed that γ-ecs, apx1, cat1, and sod2 transcription increased after 24 h of apocynin treatment in SHS 3031.

The effect of nitrogen forms on photosynthesis and anti-oxidative systems of barley plants under chromium stress was studied in a hydroponic experiment. The treatments comprised three chromium concentrations (0, 75, and 100 μM) and three N forms (NH₄)₂SO₄, urea, and Ca(NO₃)₂. In comparison with the urea or (NH₄)₂SO₄ fed plants, the Ca(NO₃)₂ fed plants had higher net photosynthetic rate, intercellular CO₂ concentration, stomatal conductance, transpiration rate, photosynthetically active radiation utilization efficiency, variable to maximum chlorophyll fluorescence ratio, and the content of chlorophylls and carotenoids. Cr toxicity caused oxidative stress in all plants but the Ca(NO₃)₂ fed plants had the least oxidative stress. Moreover, the Ca(NO₃)₂ fed plants had higher activities of anti-oxidative enzymes and content of non-enzymatic antioxidants than the urea or (NH₄)₂SO₄ fed plants. In addition, the Ca(NO₃)₂ fed plants had higher N and lower Cr content in all plant tissues than the urea or (NH₄)₂SO₄ fed plants. The current results indicate that the reasonable choice of N fertilizer is important for barley production on the Cr-contaminated soils.

Marker-free transgenic cucumber (Cucumis sativus L.) cv. Poinsett 76 SR plants were produced by Agrobacterium mediated transformation. A transformation efficiency of 1.62 was observed on using Agrobacterium tumefaciens strain LBA4404 harbouring Arabidopsis cbf1 gene driven by the inducible promoter RD29A in a binary vector system pCAMBIA. Transgene integration and single copy insert in transgenic cucumber was confirmed by polymerase chain reaction (PCR) and Southern blot analysis in T₀ lines and also confirmed marker-free status in T₁ generation. Transgene expression was confirmed by reverse transcription (RT)-PCR in T₁ generation transgenic cucumber and advanced to T₂ generation. Upon exposure to chilling stress (4 °C), the T₂ generation transgenic plants survived up to 36 h; however, wild-type plants could not survive and gradually died. A significant decrease in membrane injury index (MII), increase in activities of antioxidant enzymes (SOD and CAT), free proline content and relative water content (RWC) in the leaves were observed in transgenic cucumber as compared to wild-type under chilling stress. Thus, the transgenic cucumber plants expressing Arabidopsis cbf1 gene conferred protection against chilling stress.

The leaf apoplast is a dynamic compartment in contact with plant pathogenic bacteria after infection. Among the very first interaction events is the receptor-mediated perception of bacterial surface molecules such as flagellin or other conserved microbe-associated molecular patterns (MAMPs). Apoplast proteins likely play a role in basal resistance (BR) or pattern-triggered immunity (PTI). Here, a proteomic approach was carried out on water soluble - potentially the most mobile - apoplast proteins from flagellin-treated tobacco (Nicotiana tabacum) leaves. As the quickness of BR/PTI seems crucial for its efficacy, samples were taken as early as 2.5 and 7 h post inoculation. Proteins were separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and identified by liquid chromatography tandem mass spectrometry (LC-MS/MS). Forty-nine different proteins from 28 protein spots changed in their density compared to the water-inoculated control. Eleven protein spots appeared de novo in response to EBR induction. There are glycohydrolases and redox-active proteins besides pathogenesis-related proteins among them, predicting plant cell wall structural modifications and more direct antimicrobial effectors as earliest changes related to BR/PTI.

An AREB gene, designated as AhAREB1, was cloned from peanut (Arachis hypogaea L.). The gene contains a 1 338-bp open reading frame that encodes a putative protein of 445 amino acids. The corresponding genomic DNA containing four exons and three introns was isolated and analyzed. An upstream 1 060-bp DNA promoter fragment of the AhAREB1 gene was also amplified from peanut genomic DNA. Multiple sequence alignment of the deduced amino acids of AREB showed that the AhAREB1 protein shares high sequence homology with GmAREB1, S1AREB and ABF2. Quantitative real-time PCR analysis showed that AhAREB1 was induced by polyethylene glycol, NaCl, gibberellic acid, abscisic acid and salicylic acid. The cloning and characterization of the AhAREB1 gene will be useful for further studies establishing the biological role of AhAREB1 in plants.

In this article, we present the response of Medicago truncatula Gaert. cv. Jemalong plants expressing constitutively the Dsp22 gene from Craterostigma plantagineum to water stress and rehydration. The Dsp22 gene encodes an ELIP-like protein thought to protect the chloroplast against photooxidative damage during the dehydration and rehydration. The Dsp22 transgenic homozygous M. truncatula plants showed higher amount of chlorophyll (Chl), lower Chl a/Chl b ratio and higher actual efficiency of energy conversion in photosystem 2 (Φ_PSII) after rehydration, when compared to the wild type. The combined data from the Chl a fluorescence analysis, pigment quantification and biomass accumulation showed that transgenic M. truncatula plants are able to recover from water deprivation better than wild type plants.

Date palm (Phoenix dactylifera L.) cv. Khenizi caulogenic meristems were initiated from achlorophyllous leaves excised from in vitro shoot cultures and then proliferated on a specific culture medium supplemented with 70 g dm^-3 sucrose. Regeneration rates obtained when using standard vitrification, droplet-vitrification, and encapsulation-vitrification protocols reached 26.7, 60.0, and 40.0 %, respectively. Only explants smaller than 3 mm in diameter were found to survive cryogenic treatments. Sucrose preculture, cold hardening and loading solution pretreatments showed significant effects on regeneration rates. Moreover, our results indicate that both sucrose preculture and cold acclimation of explants increased proline content. Cryopreservation of date palm tissue with high proliferation capacity can directly benefit large scale micropropagation projects.

This study aimed to investigate seed germination, seedling growth, and antioxidative responses in two wheat cultivars, Ningchun and Xihan, exposed to different H₂O₂ concentrations. Ningchun exhibited higher germination rate but lower root and shoot growth than Xihan when exposed to H₂O₂ treatment. Assays using fluorescent dye H₂DCFDA and propidium iodide showed a significantly enhanced H₂O₂ content and a cell elongation inhibition in H₂O₂-treated roots. The malondialdehyde content was elevated with increasing exogenous H₂O₂ concentration. Moreover, treatments of seedlings with H₂O₂ scavenger, catalase (CAT), and antioxidant, butylated hydroxytoluene, partly abolished H₂O₂-induced negative effect on root growth. In both untreated and H₂O₂-treated leaves, SOD activity in Ningchun was higher than that in Xihan, but POD and APX activities in Ningchun were lower than those in Xihan, leading to elevated H₂O₂ level in Ningchun leaves but decreased H₂O₂ content in Xihan ones under H₂O₂ treatment.

During the first year of hybrid poplar development, we assessed radial growth dynamics quantified by the proportion of secondary xylem tissue within the stem area, the vessel area percentage, the content of both lignin and cellulose, the lignin monomeric composition, and the macromolecular properties of cellulose. The intraannual radial growth dynamics in the proportion of secondary xylem tissue was fitted by the Gompertz regression line whereas changes in the vessel area percentage were fitted maximally by a cubic regression line. Under constant temperature and photoperiod, this study revealed that nonlinear patterns of radial growth dynamics are the result of a developmental programme which drives cambial activity and ageing. The increased proportion of guaiacyl units found may be important for the greater stability of the lignin structure in the first year of hybrid poplar development. The tensile strength of juvenile wood was ensured by the trade-off between a slight increase in the degree of polymerization of cellulose and a slight decrease in the content of cellulose during ageing.

Treatment with 0.5 mM salicylic acid (SA) significantly alleviated growth inhibition induced by drought in wheat seedlings, manifested by less decreassed fresh mass, dry mass, plant height, root length, and less increased lipid peroxidation. Under drought stress, SA significantly increased the content of ascorbate (ASA) and glutathione (GSH). We determined the full-length cDNA sequences of genes encoding the glutathione-S-transferase 1 (GST1) and 2 (GST2) and we also measured the transcription of eight genes related to ASA-GSH cycle. The results indicated that exogenous SA significantly enhanced the transcription of GST1, GST2, glutathione reductase (GR), and monodehydroascorbate reductase (MDHAR) genes during almost the entire drought period, but only increased those of dehydroascorbate reductase (DHAR) at 12 h, glutathione peroxidase (GPX1) at 48 h, phospholipid hydroperoxide glutathione peroxidase (GPX2) at 12 and 24 h, and glutathione synthetase (GSHS) at 12, 24, and 48 h. This implies that SA alleviates the detrimental effects of drought stress on wheat seedling growth by influencing the ASA-GSH cycle.

Antioxidative responses and proline accumulation induced by exogenous H₂O₂ were investigated in the callus from halophyte Nitraria tangutorum Bobr. H₂O₂-treated callus exhibited higher H₂O₂ content than untreated callus. The activities of catalase (CAT) and peroxidase (POD) significantly increased in the callus treated with H₂O₂, while ascorbate peroxidase (APX) activity decreased. In addition, significantly enhanced proline content was observed in the callus treated by H₂O₂, which could be alleviated by H₂O₂ scavenger dimethylthiourea and calcium (Ca) chelator ethylene glycol bis-(β-aminoethyl ether)-N,N,N',N'-tetra-acetic acid (EGTA). Moreover, γ-glutamyl kinase (GK) activity increased in H₂O₂-treated callus, but proline dehydrogenase (PDH) activity decreased significantly, and the reduction was partly abolished by EGTA or Ca channel blocker verapamil. Assays using a scanning electron microscope showed significantly enhanced Ca content in H₂O₂-treated callus.

The relationship between somatic embryogenesis (SE) and the expression of the BABY BOOM (BBM) gene was studied in cultured immature zygotic embryos (IZEs) using a transgenic line of Arabidopsis thaliana containing a BBMPro::GUS construct. Results showed spatio-temporal differences in BBM expression in explants during culture. BBM promoter activity was observed in freshly isolated IZEs except distal parts of cotyledons. At the beginning of culture, considerable increase of GUS staining intensity was observed in all parts of explants, which maintained at high level over next few days and coincide with cell divisions. Gradual decrease of GUS distribution in explants was observed at about the 5th day of culture. BBM promoter activity became largely restricted to dividing cells, then to developing somatic embryos, shoot-like structures and callus. In parts of explants not involved in morphogenesis BBM promoter activity was absent or hardly seen. Thus the in vitro expression of BBM coincides with cell proliferation and morphogenesis.

Glutathione-S-transferases (GSTs) are ubiquitous enzymes that play a key role in stress tolerance and cellular detoxification. The GST gene GsGST14 selected from the gene expression profiles of Glycine soja under alkaline stress was transformed into alfalfa (Medicago sativa L.). Transgenic alfalfa plants showed 1.73-1.99 times higher GST activity than wild-type plants. Transgenic alfalfa grew well in the presence of 100 mM NaHCO₃, while wild-type plants exhibited chlorosis and stunted growth, even death. There were marked changes in malondialdehyde content and relative membrane permeability caused by alkaline stress in non-transgenic lines compared to transgenic lines. The results indicate that the gene GsGST14 could enhance alkaline resistance in transgenic alfalfa.

Mature embryonic axes were used for chickpea (Cicer arietinum L.) regeneration via somatic embryogenesis. Qualitative and quantitative estimation of protein profile during somatic embryogenesis by SDS-PAGE and densitometric analysis showed differential expression of various storage proteins at different stages of somatic embryo development, which was compared with the profile of developing seeds. Total protein content in somatic embryos of chickpea increased from globular stage [2.9 μg mg^-1(f.m.)] to cotyledonary stage [4.8 μg mg^-1(f.m.)] and then started decreasing during onset of maturation and germination [up to 1.5 μg mg^-1(f.m.)]. Differential expression of seed storage proteins, late embryogenesis abundant (LEA) proteins and proteins related with stress response were documented at different stages of somatic embryogenesis. Germinating somatic embryos showed degradation products of several seed storage proteins and the appearance of new polypeptides (76.8, 67.6, 49.9 and 34.2 kDa), which were absent during differentiation of somatic embryos. A low molecular mass (17.7 kDa) polypeptide was uniformly present during all stages of somatic embryogenesis and it may belong to a group of stress-related proteins. This study describes the expression of true seed storage proteins like legumin, vicilin, convicilin and their subunits at different stages of somatic embryogenesis, which may serve as excellent markers for embryogenic pathway of regeneration in chickpea.