Direct Organogenesis of Citrus Cultivars from Shoot Tip Nodal Segments

BACKGROUND

Citrus cultivar improvement via conventional breeding strategies is impeded by factors related to its reproductive biology. The orange is a hybrid between pomelo (Citrus maxima) and mandarin (Citrus reticulata). Among various orange cultivars, Valencia oranges have a bit of bitter tang mixed in with their sweetness, as Navel oranges are, the most widely cultivated citrus species, quite sweeter, and also don't contain any seeds. Tangelo mandarin orange cultivar is a hybrid of C. reticulata × C. maxima or × C. paradisi.

OBJECTIVE

The present study was undertaken to optimize the hormonal composition of the media with regard to plant growth regulators for in vitro propagation of sweet orange cultivars from nodal segment explants.

METHODS

The nodal segment explants were collected from three citrus cultivars, Washington Navel, Valencia and Tangelo. Murashige and Skoog (MS) medium supplemented with sucrose and different concentrations of growth regulators was used for shoot proliferation and root induction, and the optimum medium composition was assessed. The patent for Citrus Tissue Culture was obtained from the Office of Research Affairs, Haramaya University.

RESULTS

The results indicate that the highest shoot response was recorded for Washington's navel with maximum shoot proliferation rate (99.75%), shoot number per explant (1.76), shoot length (10.70 cm), leaf number per explants (3.54) after three weeks of culture. In all experiments, no growth was observed for the basal MS medium. Phytohormone combinations of IAA (1.2 mg/L) and kinetin (2.0 mg/L) were found to be the best for shoot proliferation. Among the cultivars, there were significant differences for the highest rooting rate (81.255), root number (2.22), and root length (2.95 cm) variables for Washington Navel. The lowest rooting rate (48.45%), root number (1.47) and root length (2.26 cm) were observed for Valencia. The highest rooting rate (84.90%), root number per microshoot (2.22) and root length (3.05 cm) was on MS medium supplemented with 1.5 mg/L NAA.

CONCLUSION

A comparison of different concentrations of IAA and NAA on root induction of microshoots from nodal segments of citrus cultivars demonstrated NAA was a more effective hormone than IAA.

A Versatile Protocol for Efficient Transformation and Regeneration in Mega Indica Rice Cultivar MTU1010: Optimization through Hormonal Variables

Rice is one of the apex food crops in terms of meeting the daily calorific and dietary requirement of the majority of the world population. However, rice productivity is severely limited by various biotic and abiotic attributes, causing a severe threat to global food security. In the use of functional genomics and genome editing for the generation of trait-enhanced genotypes, it is necessary to have an efficient genetic transformation and regeneration protocol. The recalcitrant nature and paucity of efficient and versatile genetic transformation and regeneration protocols for indica cultivars remains a constraint. In the present study, we have optimized a tissue culture method for MTU1010, a mega indica rice variety. We conducted a combinatorial analysis of different plant growth regulators on embryogenic callus induction efficiency, and it was observed that MSB5 medium supplemented with 2.5 mg/L 2-4D and 0.25 mg/L 6-BAP results in maximum embryogenic callus induction, i.e., 92%. The regeneration efficiency of a transformed callus can be enhanced by up to 50% with the supplementation of 1 mg/L kinetin alongside 2.5 mg/L BAP and 0.5 mg/L NAA in the shooting medium. Furthermore, our results unveiled that the pre-activation of Agrobacterium culture for 30 min with 150 µM acetosyringone significantly increased the transformation efficiency of calli. Additionally, descaling the salt concentration to half strength in resuspension and co-cultivation increased the efficiency of transformation up to 33%. Thus, the protocol developed in this study will be instrumental for the genome editing and genetic engineering of indica rice cultivars for functional genomics studies and crop improvement.

The Gold(I) Complex with Plant Hormone Kinetin Shows Promising In Vitro Anticancer and PPARγ Properties

Motivated by the clinical success of gold(I) metallotherapeutic Auranofin in the effective treatment of both inflammatory and cancer diseases, we decided to prepare, characterize, and further study the [Au(kin)(PPh₃)] complex (1), where Hkin = kinetin, 6-furfuryladenine, for its in vitro anti-cancer and anti-inflammatory activities. The results revealed that the complex (1) had significant in vitro cytotoxicity against human cancer cell lines (A2780, A2780R, PC-3, 22Rv1, and THP-1), with IC₅₀ ≈ 1-5 μM, which was even significantly better than that for the conventional platinum-based drug Cisplatin while comparable with Auranofin. Although its ability to inhibit transcription factor NF-κB activity did not exceed the comparative drug Auranofin, it has been found that it is able to positively influence peroxisome-proliferator-activated receptor-gamma (PPARγ), and as a consequence of this to have the impact of moderating/reducing inflammation. The cellular effects of the complex (1) in A2780 cancer cells were also investigated by cell cycle analysis, induction of apoptosis, intracellular ROS production, activation of caspases 3/7 and disruption of mitochondrial membrane potential, and shotgun proteomic analysis. Proteomic analysis of R2780 cells treated with complex (1) and starting compounds revealed possible different places of the effect of the studied compounds. Moreover, the time-dependent cellular accumulation of copper was studied by means of the mass spectrometry study with the aim of exploring the possible mechanisms responsible for its biological effects.

Role of Phytohormones in Biomass and Polyphenol Accumulation in Salvia bulleyana In Vitro Culture

Salvia bulleyana is a plant native to the Chinese Yunnan Province. This species has been used in traditional Chinese medicine as a substitute for Danshen (the roots of Salvia miltiorrhiza). The aim of our study was to establish an effective system for propagating S. bulleyana shoots to obtain large amounts of material rich in bioactive compounds. Phytohormones were used to regulate shoot growth and regeneration potential and influence plant secondary metabolism. The shoot tips were incubated on a Murashige and Skoog agar medium supplemented with 0.1 or 0.5 mg/L IAA (indole-3-acetic acid) and the cytokinins benzylaminopurine (BAP), meta-topoline (M-T), 6-benzylaminopurine riboside (RBAP), N-benzyl-9-(2-tetrahydropyranyl)-adenine (BPA) or kinetin, (K) at concentrations of 0.5, 1 or 2 mg/L. It was observed that the type and concentration of growth regulator significantly influenced the regeneration potential of S. bulleyana shoots. The highest multiplication rate was obtained when 0.1 mg/L IAA and 2 mg/L BPA were used. Under these conditions, 100% of shoot tips formed buds and almost seven buds/shoot per explant were obtained after five weeks. Meanwhile, the highest biomass was found for shoots growing on a medium supplemented with 0.1 mg/L IAA and 1 mg/L M-T: 1.2 g of fresh weight and 0.17 g of dry weight. However, a medium with 0.1 mg/L IAA and 2 mg/L RBAP was most favorable for bioactive phenolic acid content, with a total polyphenol level (37.7 mg/g dw) 4.5 times higher than in shoots grown on medium without growth regulators (8.23 mg/g dw). Finally, optimal conditions were selected by TOPSIS (technique for order of preference by similarity to the ideal solution); the culture of S. bulleyana grown on an MS medium containing 0.1 mg/L IAA and 1 mg/L M-T was found to be the most efficient for polyphenol accumulation and can be used for the production of medicinally relevant compounds.

Assessment of the effect of kinetin against formic acid toxicity in chicken embryo model

The current study was designed to investigate the in ovo injection of formic acid (FA) on hatchability rate (HR; Experiment 1) and the potential ameliorative role of kinetin concurrent with FA on biochemical parameters of hatched broilers (Experiment 2). In Experiment 1, live embryonated eggs (n = 280; Day 4 of incubation) were in ovo injected with 0.03, 0.06, 0.125, 0.25, 0.50, 1, 2, 4, 8, 16 and 32 m m FA. In Experiment 2, intra-yolk-sac administration of toxic doses of FA (2 m m) concurrent with kinetin at 50, 100 or 200 µ m were evaluated on hatched embryos. The amount of malondialdehyde (MDA), total antioxidant capacity (TAC), total nitrate-nitrite (TNN), total lipid hydroperoxide (TLHP) and superoxide dismutase (SOD) activity was measured in serum, liver, heart and brain tissues. The results revealed that injection of 2 mM FA significantly increased mortality compared to the control group (p < 0.05). Concurrent administration of 50 or 100 µ m kinetin + 2 m m FA increased HR to 10% and 20% compared to the FA-alone-treated group, respectively. Intra-yolk-sac-received FA group showed greater amounts of MDA, TLHP and TNN and lesser amounts of TAC and SOD activity in serum and tissue samples of liver, heart and brain compared to control groups (p < 0.001). In comparison to the FA-alone-treated group, all doses of kinetin were able to increase the TAC levels in serum and tissue samples when administered concurrently with FA. The doses of 50 and 100 µ m kinetin were efficacious to ameliorate the toxic role of FA injection on SOD activities (p < 0.001). Co-injection of 100 µ m kinetin plus FA significantly reduced the amounts of MDA, TNN and TLHP in measured samples compared to the FA-alone-injected group (p < 0.001). Our results indicated that kinetin (especially at 100 µ m doses) would ameliorate the toxic effects of FA on developing live chicken embryos.

Increased mitophagy protects cochlear hair cells from aminoglycoside-induced damage

Aminoglycosides exhibit ototoxicity by damaging mitochondria, which in turn generate reactive oxygen species that induce hair cell death and subsequent hearing loss. It is well known that damaged mitochondria are degraded by mitophagy, an important mitochondrial quality control system that maintains mitochondrial homeostasis and ensures cell survival. However, it is unclear whether dysregulation of mitophagy contributes to aminoglycoside-induced hair cell injury. In the current study, we found that PINK1-PRKN-mediated mitophagy was impaired in neomycin-treated hair cells. Our data suggested that mitochondrial recruitment of PRKN and phagophore recognition of damaged mitochondria during mitophagy were blocked following neomycin treatment. In addition, the degradation of damaged mitochondria by lysosomes was significantly decreased as indicated by the mitophagic flux reporter mt-mKeima. Moreover, we demonstrated that neomycin disrupted mitophagy through transcriptional inhibition of Pink1 expression, the key initiator of mitophagy. Moreover, we found that neomycin impaired mitophagy by inducing ATF3 expression. Importantly, treatment with a mitophagy activator could rescue neomycin-treated hair cells by increasing mitophagy, indicating that genetic modulation or drug intervention in mitophagy may have therapeutic potential for aminoglycoside-induced hearing loss.Abbreviations: AAV: adeno-associated virus; ABR: auditory brainstem response; ATF3: activating transcription factor 3; ATOH1/MATH1: atonal bHLH transcription factor 1; BafA1: bafilomycin A₁; CCCP: carbonyl cyanide m-chlorophenyl hydrazone; COX4I1/COXIV: cytochrome c oxidase subunit 4I1; CTBP2/RIBEYE: C-terminal binding protein 2; DFP: deferiprone; EGFP: enhanced green fluorescent protein; FOXO3: forkhead box O3; GRIA2/GLUR2: glutamate receptor, ionotropic, AMPA2 (alpha 2); HC: hair cell; HSPD1/HSP60: heat shock protein 1 (chaperonin); IHC: inner hair cell; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MYO7A: myosin VIIA; OPTN: optineurin; OMM: outer mitochondrial membrane; PRKN: parkin RBR E3 ubiquitin protein ligase; PINK1: PTEN induced putative kinase 1; RT-qPCR: real-time quantitative polymerase chain reaction; TOMM20/TOM20: translocase of outer mitochondrial membrane 20; TUNEL: Terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling; USP30: ubiquitin specific peptidase 30; XBP1: X-box binding protein 1.

Mitigation of Negative Effects of Chromium (VI) Toxicity in Faba Bean (Vicia faba) Plants through the Supplementation of Kinetin (KN) and Gibberellic Acid (GA3)

The present study was carried out to explore the possible role of kinetin and gibberellic acid (GA3) on faba bean under chromium (Cr) stress. Cr treatment negatively affected growth and biomass production, reduced photosynthetic pigments, and inhibited photosynthesis, gas exchange parameters, antioxidant enzymes, and the glyoxylase cycle. Moreover, Cr stress enhanced the production of malondialdehyde (MDA, 216.11%) and hydrogen peroxide (H₂O₂, 230.16%), electrolyte leakage (EL, 293.30%), and the accumulation of proline and glycine betaine. Exogenous application of kinetin and GA3 increased growth and biomass, improved pigment contents and photosynthesis, as well as up-regulated the antioxidant system by improving the antioxidant enzyme activities and the content of nonenzymatic components, and the glyoxylase cycle. Additionally, kinetin and GA3 application displayed a considerable enhancement in proline (602.61%) and glycine betaine (423.72), which help the plants to maintain water balance under stress. Furthermore, a decline in Cr uptake was also observed due to kinetin and GA3 application. Exogenous application of kinetin and GA3 ameliorated the toxic effects of Cr in faba bean plants, up-shooting the tolerance mechanisms, including osmolyte metabolism and the antioxidant system.

Cisplatin-Induced Reproductive Toxicity and Oxidative Stress: Ameliorative Effect of Kinetin

Cisplatin is a commonly used chemotherapeutic agent; however, its potential side effects, including gonadotoxicity and infertility, are a critical problem. Oxidative stress has been implicated in the pathogenesis of cisplatin-induced testicular dysfunction. We investigated whether kinetin use at different concentrations could alleviate gonadal injury associated with cisplatin treatment, with an exploration of the involvement of its antioxidant capacity. Kinetin was administered in different doses of 0.25, 0.5, and 1 mg/kg, alone or along with cisplatin for 10 days. Cisplatin toxicity was induced via a single IP dose of 7 mg/kg on day four. In a dose-dependent manner, concomitant administration of kinetin with cisplatin significantly restored testicular oxidative stress parameters, corrected the distorted sperm quality parameters and histopathological changes, enhanced levels of serum testosterone and testicular StAR protein expression, as well as reduced the up-regulation of testicular TNF-α, IL-1β, Il-6, and caspase-3, caused by cisplatin. It is worth noting that the testicular protective effect of the highest kinetin dose was comparable/more potent and significantly higher than the effects of vitamin C and the lowest kinetin dose, respectively. Overall, these data indicate that kinetin may offer a promising approach for alleviating cisplatin-induced reproductive toxicity and organ damage, via ameliorating oxidative stress and reducing inflammation and apoptosis.

Comparative Analysis of Enzymatic Transglycosylation Using E. coli Nucleoside Phosphorylases: A Synthetic Concept for the Preparation of Purine Modified 2′-Deoxyribonucleosides from Ribonucleosides

A comparative analysis of the transglycosylation conditions catalyzed by E. coli nucleoside phosphorylases, leading to the formation of 2'-deoxynucleosides, was performed. We demonstrated that maximal yields of 2'-deoxynucleosides, especially modified, can be achieved under small excess of glycosyl-donor (7-methyl-2'-deoxyguanosine, thymidine) and a 4-fold lack of phosphate. A phosphate concentration less than equimolar one allows using only a slight excess of the carbohydrate residue donor nucleoside to increase the reaction's output. A three-step methodology was elaborated for the preparative synthesis of purine-modified 2'-deoxyribonucleosides, starting from the corresponding ribonucleosides.

Diverse Effect of Two Cytokinins, Kinetin and Benzyladenine, on Plant Development, Biotic Stress Tolerance, and Gene Expression

The plant hormones cytokinins affect a various array of plant growth and development processes as well as responses to biotic and abiotic stresses. In this study, the opposite effect of two different cytokinins kinetin (N⁶-furfuryladenine) and benzyladenine (BA) on development and on the tolerance of Arabidopsis and tobacco plants to virus, bacteria, and fungi infection was reported. Treatments of Arabidopsis and tobacco seedlings with saturated solutions of BA inhibited plant progress, while treatments with saturated water solution of kinetin promoted plant development. Furthermore, BA pre-treatments strongly reduced the number of TMV (Tobacco mosaic virus) lesions on tobacco and the tissue damage caused by the incompatible Pseudomonas bacteria on Arabidopsis and tobacco leaves. Similarly, BA pre-treatment significantly reduced the necrotic disease symptoms of Botrytis cinerea infection. Kinetin pre-treatments had a much weaker or no protective effect on the damage caused by the above pathogens. Accordingly, Arabidopsis gene expression profiles after treatments also showed that the two cytokinins have different effects on several plant processes. The gene expression results supported the more robust effect of BA, which up and downregulated more than 2000 genes, while only 436 genes were influenced by kinetin treatment. It is noteworthy that BA and kinetin treatment changed gene expressions in the same direction only in a relatively few cases (73 upregulated and 70 downregulated genes), and even 28 genes were regulated into the opposite directions by BA and kinetin. Both treatments had a strong effect on auxin and gibberellin-related genes, but only BA had a significant effect on cytokinin-induced processes. While kinetin exclusively activated the flavonoid synthesis genes, BA affected more significantly protein synthesis, photosynthesis, and plant defence-related genes. In conclusion, BA solution had sometimes the opposite and generally a much stronger effect than kinetin solution not only on the development and on biotic stress tolerance of tobacco and Arabidopsis plants but also on the gene expressions. The stronger protective effect of BA to necrotic stresses is probably due to its stronger senescence inhibitory effect on plant tissues, as supported by the stronger chlorophyll retardation of the BA-treated leaves.

6-Benzylaminopurine Alleviates the Impact of Cu2+ Toxicity on Photosynthetic Performance of Ricinus communis L. Seedlings

Copper (Cu) is an essential element involved in various metabolic processes in plants, but at concentrations above the threshold level, it becomes a potential stress factor. The effects of two different cytokinins, kinetin (KIN) and 6-benzylaminopurine (BAP), on chlorophyll a fluorescence parameters, stomatal responses and antioxidation mechanisms in castor (Ricinus communis L.) under Cu²⁺ toxicity was investigated. Ricinus communis plants were exposed to 80 and 160 μM CuSO₄ added to the growth medium. Foliar spraying of 15 μM KIN and BAP was carried out on these seedlings. The application of these cytokinins enhanced the tissue water status, chlorophyll contents, stomatal opening and photosynthetic efficiency in the castor plants subjected to Cu²⁺ stress. The fluorescence parameters, such as Fm, Fv/Fo, Sm, photochemical and non-photochemical quantum yields, energy absorbed, energy trapped and electron transport per cross-sections, were more efficiently modulated by BAP application than KIN under Cu²⁺ toxicity. There was also effective alleviation of reactive oxygen species by enzymatic and non-enzymatic antioxidation systems, reducing the membrane lipid peroxidation, which brought about a relative enhancement in the membrane stability index. Of the various treatments, 80 µM CuSO₄ + BAP recorded the highest increase in photosynthetic efficiency compared to other cytokinin treatments. Therefore, it can be concluded that BAP could effectively alleviate the detrimental effects of Cu²⁺toxicity in cotyledonary leaves of R. communis by effectively modulating stomatal responses and antioxidation mechanisms, thereby enhancing the photosynthetic apparatus’ functioning.

Exogenous Kinetin Promotes the Nonenzymatic Antioxidant System and Photosynthetic Activity of Coffee (Coffea arabica L.) Plants Under Cold Stress Conditions

Coffee plants are seasonally exposed to low chilling temperatures in many coffee-producing regions. In this study, we investigated the ameliorative effects of kinetin-a cytokinin elicitor compound on the nonenzymatic antioxidants and the photosynthetic physiology of young coffee plants subjected to cold stress conditions. Although net CO2 assimilation rates were not significantly affected amongst the treatments, the subjection of coffee plants to cold stress conditions caused low gas exchanges and photosynthetic efficiency, which was accompanied by membrane disintegration and the breakdown of chlorophyll pigments. Kinetin treatment, on the other hand, maintained a higher intercellular-to-ambient CO2 concentration ratio with concomitant improvement in stomatal conductance and mesophyll efficiency. Moreover, the leaves of kinetin-treated plants maintained slightly higher photochemical quenching (qP) and open photosystem II centers (qL), which was accompanied by higher electron transfer rates (ETRs) compared to their non-treated counterparts under cold stress conditions. The exogenous foliar application of kinetin also stimulated the metabolism of caffeine, trigonelline, 5-caffeoylquinic acid, mangiferin, anthocyanins and total phenolic content. The contents of these nonenzymatic antioxidants were highest under cold stress conditions in kinetin-treated plants than during optimal conditions. Our results further indicated that the exogenous application of kinetin increased the total radical scavenging capacity of coffee plants. Therefore, the exogenous application of kinetin has the potential to reinforce antioxidant capacity, as well as modulate the decline in photosynthetic productivity resulting in improved tolerance under cold stress conditions.

Protocol of <i>in vitro</i> Jojoba (<i>Simmondsia chinensis</i> (Link) Schneider) Callus Induction

BACKGROUND AND OBJECTIVES

Presently, determination of optimum protocol for callus induction of any plant is an important issue in tissue culture technology. Therefore, the main objective of this study was to find out an optimum protocol for callus induction from in vitro cultured jojoba by determining the optimum explant and the best growth regulators mixture for callus induction.

MATERIALS AND METHODS

The study used three variant explants namely the leaf disks, seeds and nodal segments for callus formation. Different culture media containing basic Murashige and Skoog (MS) medium components supplemented with various concentrations of 2,4-dichlorophenoxy acetic acid as an auxin (2,4-D) and Kinetin (Kin) as a cytokinin with various concentrations ranging from 0.0, 0.5, 1.0 and 2.0 mg L-1 were used. The total number of treatments were 16. The callus was induced from all explants on MS medium containing the lowest concentration of 2,4-D 0.5 mg L-1 with any concentration of Kin.

RESULTS

The results showed that nodal segments were the best for callus formation followed by the leaf disks (leaves) and seeds, respectively. While, the best concentration of proliferation and development of the used explant was 2.00 followed in descending order by 1.00, 0.5 and 0.0 mg L-1, respectively.

CONCLUSION

The study find out that the best concentration of 2,4-dichlorophenoxy acetic acid as an auxin (2,4-D) and Kinetin (Kin) as a cytokinin was 2.00 followed in descending order by 1.00, 0.5 and 0.0 mg L-1, respectively for callus induction.

DNA Repair Signaling of Huntingtin: The Next Link Between Late-Onset Neurodegenerative Disease and Oxidative DNA Damage

A new hypothesis for the mechanism of Huntington's disease (HD) is driven by a small molecule lead that may connect age-associated reactive oxygen stress, oxidative DNA damage, and mitochondrial dysfunction. These pathways have also recently been defined in genome-wide association studies of cytosine-adenine-guanine-expansion polyglutamine neurodegenerative diseases, including HD and the spinocerebellar ataxias. We discuss how N6-furfuryladenine (N6FFA) nucleotide salvage and role as a kinase neosubstrate may have important mechanistic implications for both HD and familial Parkinson's disease. N6FFA highlights a mechanism of how energy dysregulation and protein misfolding in neurodegeneration may be the effect of age-associated reactive oxygen species damage to DNA and part of a feedback loop augmenting with aging.

Kinetin inhibits proliferation of hepatic stellate cells by interrupting cell cycle and induces apoptosis by down-regulating ratio of Bcl-2/Bax

Liver fibrosis is an important health problem that can further progress into cirrhosis or liver cancer, and result in significant morbidity and mortality. Inhibiting proliferation and inducing apoptosis of hepatic stellate cells (HSCs) may be the key point to reverse liver fibrosis. At present, anti-fibrosis drugs are rare. Kinetin is a type of plant-derived cytokinin which has been reported to control differentiation and induce apoptosis of human cells. In this study, the HSCs were incubated with different concentrations of kinetin. The proliferation of rat HSCs was measured by MTT assay, cell cycle and apoptosis were analyzed by flow cytometry, and the apoptosis was examined by TUNEL method. The expression of Bcl-2 and Bax proteins was detected by immunocytochemistry staining. It was found that kinetin could markedly inhibit proliferation of HSCs. In a concentration range of 2 to 8 μg/mL, the inhibitory effects of kinetin on proliferation of HSCs were increased with the increased concentration and the extension of time (P < 0.01). Flow cytometry indicated that kinetin could inhibit the DNA synthesis from G0/G1 to S phase in a dose-dependent manner (P < 0.01). The apoptosis rates of the HSCs treated with 8, 4 and 2 μg/mL kinetin (25.62% ± 2.21%, 15.31% ± 1.9% and 6.18% ± 1.23%, respectively) were increased significantly compared with the control group (3.81% ± 0.93%) (P < 0.01). All the DNA frequency histogram in kinetin-treated groups showed obvious hypodiploid peak (sub-G1 peak), and with the increase of kinetin concentrations, the apoptosis rate of HSCs also showed a trend of increase. It was also found that kinetin could down-regulate the expression of Bcl-2, and up-regulate the expression of Bax, leading to the decreased ratio of Bcl-2/Bax significantly. The kinetin-induced apoptosis of HSCs was positively correlated with the expression of Bax, and negatively with the expression of Bcl-2. It was concluded that kinetin can inhibit activation and proliferation of HSCs by interrupting the cell cycle at G1/S restriction point and inducing apoptosis of HSCs via reducing the ratio of Bcl-2/Bax.

Kinetin modulates physio-hormonal attributes and isoflavone contents of Soybean grown under salinity stress

Crop productivity continues to decline due to a wide array of biotic and abiotic stresses. Salinity is one of the worst abiotic stresses, as it causes huge losses to crop yield each year. Kinetin (Kn) has been reported as plant growth regulator since long, but its role in improving plant growth and food quality under saline conditions through mediating phytohormonal cross-talk is poorly studied. Current study was designed to evaluate the impact of exogenously applied Kn on growth, isoflovones and endogenous phytohormones of soybean grown under NaCl induced salt stress. Soybean plants were grown in perlite (semi hydroponic), and under controlled green-house conditions. Elevated levels of exogenous Kn significantly mitigated the adverse effect of NaCl and rescued plant growth attributes, i.e., plant height, fresh and dry biomass of soybean plants grown in all treatments. Higher diadzen, glycitin, and genistin contents were observed in plants treated with elevated Kn in the presence or absence of NaCl induce salt stress. The gibberellins (GAs) biosynthesis pathway was up-regulated by Kn as the bioactive GA1 and GA4 contents were significantly higher in Kn treated plants, as compared to control, while GAs level reduced in NaCl treated plants. Contrary to GAs, the abscisic acid contents declined with Kn but promoted in NaCl stressed soybean plants. The endogenous jasmonic acid and salicylic acid contents of soybean enhanced with elevated Kn application, but they showed an antagonistic response under salt stress. Current study supports the active role of Kn to ameliorate the adverse effects of salt stress on the growth and food quality of soybean. The favorable role of Kn toward soybean growth under salt stress may be attributed to its potential to modulate cross-talk between the various phytohormones involved in soybean growth and its resistance to salinity stress.

Kinetin inhibits apoptosis of aging spleen cells induced by D-galactose in rats

Kinetin (Kn) is a cytokinin growth factor that exerts several anti-aging and antioxidant effects on cells and organs. To investigate the mechanism underlying apoptotic events in aging cells induced by D-galactose (D-gal), we examined the effect of Kn delivered via nuchal subcutaneous injection on D-gal-induced aging and apoptosis in rats. Our results showed that interleukin (IL)-2 levels and mitochondrial membrane potential (ΔΨm) were decreased by Kn in aging rats while IL-6 production and apoptosis increased. In addition, the expression of anti-apoptotic Bcl-2 was low while that of Bax was high in the aging group. After treated with Kn, compared with aging group, there showed obvious difference in Kn group with elevated IL-2, proliferation index, Bcl-2, ΔΨm and decreased IL-6 and Bax in splenic lymphocyte. Based on these results, we concluded that Kn can effectively protect the rat spleen from aging, apoptosis, and atrophy.

Enhanced expression of EsWAX1 improves drought tolerance with increased accumulation of cuticular wax and ascorbic acid in transgenic Arabidopsis

Drought can activate several stress responses in plants, such as stomatal closure, accumulation of cuticular wax and ascorbic acid (AsA), which have been correlated with improvement of drought tolerance. In this study, a novel MYB gene, designed as EsWAX1, was isolated and characterized from Eutrema salsugineum. EsWAX1 contained a full-length open reading frame (ORF) of 1068 bp, which encoding 355 amino acids. Transcript levels of EsWAX1 were quickly inducible by drought stress and ABA treatment, indicating that EsWAX1 may act as a positive regulator in response to drought stress. Ectopic expression of EsWAX1 increased accumulation of cuticular wax via modulating the expression of several wax-related genes, such as CER1, KCS2 and KCR1. Scanning electron microscopy further revealed higher densities of wax crystalline structures on the adaxial surfaces of leaves in transgenic Arabidopsis plants. In addition, the expression of several AsA biosynthetic genes (VTC1, GLDH and MIOX4) was significantly up-regulated in EsWAX1-overexpressing lines and these transgenic plants have approximately 23-27% more total AsA content than WT plants. However, the high-level expression of EsWAX1 severely disrupted plant normal growth and development. To reduce negative effects of EsWAX1 over-expression on plant growth, we generated transgenic Arabidopsis plants expressing EsWAX1 driven by the stress-inducible RD29A promoter. Our data indicated the RD29A::EsWAX1 transgenic plants had greater tolerance to drought stress than wild-type plants. Taken together, the EsWAX1 gene is a potential regulator that may be utilized to improve plant drought tolerance by genetic manipulation.

Involvement of peroxidase activity in developing somatic embryos of Medicago arborea L. Identification of an isozyme peroxidase as biochemical marker of somatic embryogenesis

The legume Medicago arborea L. is very interesting as regards the regeneration of marginal arid soils. The problem is that it does not have a good germinative yield. It was therefore decided to regenerate via somatic embryogenesis and find a marker of embryogenic potential. In this study, peroxidase activity was evaluated in non-embryogenic and embryogenic calli from M. arborea L. A decrease in soluble peroxidase activity is observed in its embryonic calli at the time at which the somatic embryos begin to appear. This activity is always lower in embryonic calli than in non-embryonic ones (unlike what happens in the case of wall-bound peroxidases). These results suggest that peroxidases can be considered to be enzymes involved in somatic embryogenesis in M. arborea. In addition, isozyme analyses were carried out on protein extracts using polyacrylamide gel electrophoresis. The band called P5 was detected only in embryogenic cultures at very early stages of development. This band was digested with trypsin and analyzed using linear ion trap (LTQ) mass spectrometer. In P5 isoform a peroxidase-L-ascorbate peroxidase was identified. It can be used as a marker that allows the identification of embryological potential.

Comparative transcriptome profiles of the WRKY gene family under control, hormone-treated, and drought conditions in near-isogenic rice lines reveal differential, tissue specific gene activation

The OsWRKY genes play various roles in developmental processes and in stress-related responses in plants. We describe the rice OsWRKY gene expression profiles (GEPs) under control, hormone-treated, and water-deficit treatment (WDT) conditions. The preferential expression of 3 genes was observed in specific tissues, suggesting that these genes may play important roles in the root and panicle stages of growth. To investigate the GEPs in the root and panicle of 3 rice genotypes, we used 2 near-isogenic rice lines from a common genetic combination backcross developed by Aday Selection and IR64. WDTs were applied using the fraction of transpirable soil water (FTSW) for severe, mild, and control conditions. Transcriptomic analysis using a 44K oligoarray from Affymetrix and Agilent was performed on all the tissues. The majority of the OsWRKY genes that were activated were activated in the drought-tolerant IR77298-14-1-2-B-10 line but not in the drought-susceptible IR77298-14-1-2-B-13 or IR64 lines. In IR77298-14-1-2-B-10, non-redundant genes (9) were very specific in their higher expression levels. Approximately 27 and 43% more genes from group III and subgroup IV-a, respectively, were activated in the panicle during severe stress than during the control treatment. We found 5 OsWRKY genes that introgressed in the drought-tolerant IR77298-14-1-2-B-10 line. Os01g43650 was up-regulated in the root under both WDTs and in the panicle under mild stress. OsWRKY up-regulated genes with tissue-specific expression patterns that contained at least 3 cis-elements in the tolerant line. These results provide a useful reference for the cloning of candidate genes for further functional analysis.

A synthetic oligonucleotide model for evaluating the oxidation and crosslinking propensities of natural furan-modified DNA

We have previously developed a crosslinking methodology for oligonucleotides based on the incorporation of furan moieties, which can be selectively oxidised to reactive intermediates that will quickly react with the opposite bases in DNA, forming toxic interstrand crosslinks (ICLs). Furan moieties also occur in natural DNA, as a result of oxidative stress. Moreover, the furan-containing degradation product of this modified DNA-kinetin-has been found to display beneficial anti-ageing effects. To investigate the apparent discrepancy between the effects of the synthetic and the natural furan modifications in DNA, a quick and easy postsynthetic method providing access to the natural modification in short synthetic oligonucleotides was developed. On checking for potential crosslinking propensity, we found that the furan moiety does indeed undergo oxidation, in this way functioning as an important scavenger for oxidative stress. The reactive intermediate, however, was shown to degrade without producing toxic crosslinked products.

Plant regeneration via somatic embryogenesis and shoot organogenesis from immature cotyledons of Camellia nitidissima Chi

Camellia nitidissima Chi (Theaceae) is a world-famous economic and ornamental plant with golden-yellow flowers. It has been classified as one of the rarest and most endangered plants in China. Our objective was to induce somatic embryogenesis, shoot organogenesis and plant regeneration for C. nitidissima. Three types of callus (whitish, reddish and yellowish) were induced from immature cotyledons on improved woody plant medium (WPM) with different plant growth regulators (PGRs). Among the callus, whitish callus was induced by 4.5 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and reddish and yellowish callus were induced by strongly active cytokinins, thidiazuron (TDZ) or 6-benzylaminopurine (BAP), singly or combined with weakly active auxin, α-naphthaleneacetic acid (NAA). The embryogenic callus could differentiate into somatic embryos, nodular embryogenic structures (large embryo-like structures) or adventitious shoots depending on the PGR used in WPM. BAP was best for adventitious buds and zeatin was best for somatic embryogenesis while kinetin (Kt) was best for the formation of nodular embryogenic structures. The three regeneration pathways often occurred in the same embryogenic callus clumps. Most shoots (80.0%) developed roots in WPM supplemented with 24.6 μM IBA and 0.3 μM NAA while 47.5% of somatic embryos could germinate directly and develop into plantlets on induction medium supplemented with 0.9 μM BAP and 0.1 μM NAA. The nodular embryogenic structures could be sub-cultured and cyclically developed in one of two differentiation pathways: shoot organogenesis or somatic embryogenesis. Plantlets derived from shoot buds rooted and somatic embryos germinated when transplanted into soil in a greenhouse; 66.7% of plantlets from shoot culture and 78.6% of plantlets from somatic embryos survived after 8 weeks' acclimatization.

Genome-wide analysis of endosperm-specific genes in rice

The endosperm of the cereal crop is an important nutrient source for humans. It also acts as a critical integrator of plant seed growth and development. Despite its importance, the comprehensive understanding in regulating of endosperm development in rice remains elusive. Here, we performed a genomic survey comprising the identification and functional characterization of the endosperm-specific genes (OsEnS) in rice using Affymetrix microarray data and Gene Ontology (GO) analysis. A total of 151 endosperm-specific genes were identified, and the expression patterns of 13 selected genes were confirmed by qRT-PCR analysis. Promoter regions of the endosperm-specific expression genes were analyzed by PLACE Signal Scan Search. The results indicated that some motifs were involved in endosperm-specific expression regulation, and some cis-elements were responsible for hormone regulation. The bootstrap analysis indicated that the RY repeat (CATGCA box) was over-represented in promoter regions of endosperm-specific expression genes. GO analysis indicated that these genes could be classified into 12 groups, namely, transcription factor, stress/defense, seed storage protein (SSP), carbohydrate and energy metabolism, seed maturation, protein metabolism, lipid metabolism, transport, cell wall related, hormone related, signal transduction, and one unclassified group. Taken together, our results provide informative clues for further functional characterization of the endosperm-specific genes, which facilitate the understanding of the molecular mechanism in rice endosperm development.

Cytokinins résumé: their signaling and role in programmed cell death in plants

Cytokinins (CKs) are a large group of plant hormones which play a crucial role in many physiological processes in plants. One of the interesting functions of CKs is the control of programmed cell death (PCD). It seems that all CKs-dependent phenomena including PCD are accompanied by special multi-step phosphorelay signaling pathway. This pathway consists of three elements: histidine kinase receptors (HKs), histidine phosphotransfer proteins (HPs) and response regulators (RRs). This review shows the résumé of the latest knowledge about CKs signaling pathways in many physiological processes in plants with special attention paid to PCD process.

Antiviral Activity of Metal-Containing Polymers-Organotin and Cisplatin-Like Polymers

Polymers containing platinum and to a lesser extent tin, have repeatedly demonstrated antitumor activity in vitro and in vivo against a variety of cell and tumor types. The mechanisms responsible for the antitumor activity include inducing a delay in cell proliferation and sister chromatid exchanges blocking tumor growth. As most DNA and some RNA viruses require, and even induce, infected cells to initiate DNA replication and subsequent cell division, compounds with antitumor activity will very likely also possess antiviral activity. This article examines the use of metal-containing polymers as a novel class of antivirals.

EFFECT OF INDOLE-3-ACETIC ACID, KINETIN, AND ETHYLENEDIAMINETETRAACETIC ACID ON PLANT GROWTH AND UPTAKE AND TRANSLOCATION OF LEAD, MICRONUTRIENTS, AND MACRONUTRIENTS IN ALFALFA PLANTS

Alfalfa plants germinated and grown for 15 d in soil containing 80 mg Pb kg^-1 were treated with ethylenediaminetetraacetic acid (EDTA) at 0.8 mM and indole-3-acetic acid-kinetin (IAA-KN) at 100 μM. Fifteen days after the treatment application, the concentration of lead (Pb), macronutrients, and micronutrients was determined using inductively coupled plasma/optical emission spectroscopy. The chlorophyll content and plant growth were also measured. Roots of plants exposed to Pb alone, Pb-EDTA, and Pb-EDTA-IAA-KN had 160, 140, and 150 mg Pb kg^-1 DW, respectively. Pb was not detected in the stems of plants exposed to Pb alone; however, stems of plants treated with EDTA and EDTA-IAA-KN had 78 and 142 mg Pb kg^-1 DW, respectively. While the Pb concentration in leaves of plants treated with EDTA and EDTA-IAA-KN was 92 and 127 mg kg^-1 DW, respectively. In addition, EDTA and EDTA-IAA-KN significantly increased the translocation of zinc and manganese to leaves. The x-ray absorption spectroscopic studies demonstrated that Pb(II) was transported from roots to leaves without a change in the oxidation state.

Evaluating the function of putative hormone transporters

Hormones typically serve as long distance signaling molecules. To reach their site of action, hormones need to be transported from the sites of synthesis. Many plant hormones are mobile, thus requiring specific transport systems for the export from their source cells as well as subsequent import into target cells. Hormone transport in general is still poorly understood. Auxin is probably the most intensively studied plant hormone concerning transport in the moment. To advance our understanding of hormone transport we need two principal data sets: information on the properties of the transport systems including substrate specificity and kinetics, and we need to identify candidate genes for the respective transporters. Physiological transport data can provide an important basis for identifying and characterizing candidate transporters and to define their in vivo role. A recent publication in Plant Physiology highlights how kinetic and specificity studies may help to identify cytokinin transporters.

Comparative antimicrobial activity of callus and natural plant extracts of Solanum trilobatum L

Comparison of natural plant and callus extracts of Solanum trilobatum L. was studied against two bacteria and fungi, for their antimicrobial activity using cup diffusion method. Various solvents such as chloroform, petroleum ether and ethanol were used. The leaf and stem segments of the plant were culturedon Murashige and S koog basal medium supplemented with various growth regulators. Maximum callus was recorded on medium containing 0.5 mg/lNAA and 0.5 mgj IKinetin. The results reveals that the stem and leaf callus extracts has shown significant activity against the tested microorganisms than the natural sample.