Impacts of kinetin implementation on leaves, floral and root-related traits during seed production in hybrid rice under water deficiency.

BACKGROUND: Water deficit is one of the most significant abiotic factors affecting rice and agricultural production worldwide. In hybrid rice, cytoplasmic male sterility (CMS) is an important technique for creating high-yielding crop based on heterosis. The phytohormone kinetin (Kin) regulates cell division in plant during the early stages of grain formation, as well as flow assimilation and osmotic regulation under water stress. The present study performed to estimate the effects of irrigation intervals (irrigation each six days (I6), nine days (I9), twelve days (I12) and fifteen days (I15) against continuous flooding (CF, each three days)) and kinetin exogenously application (control, 15 mg L-1 and 30 mg L-1) on hybrid rice (L1, IR69625A; L2, G46A and R, Giza 178 R) seed production. RESULTS: Leaves traits (Chlorophyll content (CHC), relative water content (RWC), stomatal conductance (SC), Leaf temperature (LT) and transpiration rate (TR)), floral traits such as style length (SL) and total stigma length (TSL), in addition to root traits (i.e., root length (RL), root volume (RV), root: shoot ratio (RSR), root thickness (RT), root xylem vessels number (RXVN) and root xylem vessel area (RXVA) were evaluated and a significant enhancement in most traits was observed. Applying 30 mg L-1 kinetin significantly and positively enhanced all growth, floral and roots traits (RV and RXVA recorded the most increased values by 14.8% and 23.9%, respectively) under prolonging irrigation intervals, in comparison to non-treated plants. CONCLUSIONS: Subsequently, spraying kinetin exogenously on foliar could be an alternative method to reduce the harmful influences of water deficiency during seed production in hybrid rice.

Kinetin inhibits hepatic stellate cell activation and induces apoptosis via interactions with the TGF-ß1/Smad signaling pathway.

Hepatic fibrosis is the pathological repair response of the liver to chronic injury; hepatic stellate cell (HSC) activation is the central link in the pathogenesis of hepatic fibrosis. Previously, we showed that kinetin, a plant cytokinin hormone, has a protective effect on CCl4-induced liver injury in mice. However, the role of kinetin in liver fibrosis remains unclear. We aimed to study these protective effects and to determine the mechanisms by which kinetin mediates HSC activation and apoptosis. For this purpose, the human HSC line LX-2 was treated with 10 ng/ml transforming growth factor-ß1 (TGF-ß1) for 24 h to stimulate activation. We found that treatment with kinetin at the sub-cytotoxic dose of 40 µg/ml for 48 h reduced the expression of the HSC activation marker α-SMA and inhibited the secretion of extracellular matrix proteins. In addition, kinetin was found to inhibit the proliferation and migration of LX-2 cells. We found that kinetin induced apoptosis in LX-2 cells by increasing the level of cleaved-caspase 3 and the Bax-to-Bcl-2 ratio. Interestingly, these effect were not observed in quiescent HSCs, suggesting that they are activation-dependent. Further study showed that kinetin attenuates activation and promotes apoptosis of LX-2 cells in vitro in part by suppressing the TGF-ß1/Smad signaling pathway.

Photoprotective properties of new derivatives of kinetin.

The chronic exposure of skin to ultraviolet (UV) radiation causes adverse dermal reactions, such as erythema, sunburn, photoaging, and cancer, by altering several signalling pathways associated with oxidative stress, inflammation, and DNA damage. One of the possible UV light protection strategies is the use of dermal photoprotective preparations. The plant hormone kinetin (N6-furfuryladenine; KIN) exhibits antioxidant and anti-senescent effects in human cells. Topically applied KIN also reduced some of the clinical signs of photodamaged skin. To improve the biological activities of KIN, several derivatives have been recently prepared and their beneficial effects on cell viability of skin cells exposed to UVA and UVB light were screened. Two potent candidates, 6-(tetrahydrofuran-2-yl)methylamino-9-(tetrahydrofuran-2-yl)purine (HEO) and 6-(thiophen-2-yl)methylamino-9-(tetrahydrofuran-2-yl)purine (HEO6), were identified. Here the effects of KIN, its N9-substituted derivatives the tetrahydropyran-2-yl derivative of KIN (THP), tetrahydrofuran-2-yl KIN (THF), HEO and HEO6 (both THF derivatives) on oxidative stress, apoptosis and inflammation in UVA- or UVB-exposed skin cell was investigated. Human primary dermal fibroblasts and human keratinocytes HaCaT pre-treated with the tested compounds were then exposed to UVA/UVB light using a solar simulator. All compounds effectively prevented UVA-induced ROS generation and glutathione depletion in both cells. HEO6 was found to be the most potent. All compounds also reduced UVB-induced caspase-3 activity and interleukin-6 release. THP and THF exhibited the best UVB protection. In conclusion, our results demonstrated the UVA- and UVB-photoprotective potential of KIN and its derivatives. From this point of view, they seem to be useful agents for full UV spectrum protective dermatological preparations.

Increase in ENHANCER OF SHOOT REGENERATION2 expression by treatment with strigolactone-related inhibitors and kinetin during adventitious shoot formation in ipecac.

KEY MESSAGE: Increase of ENHANCER OF SHOOT REGENERATION 2 expression was consistent to treatment with kinetin, TIS108, and KK094 in adventitious shoot formation of ipecac. Unlike many plant species, ipecac (Carapichea ipecacuanha (Brot.) L. Andersson) can form adventitious shoots in tissue culture without cytokinin (CK) treatment. Strigolactone (SL) biosynthesis and signaling inhibitors stimulate adventitious shoot formation in ipecac, suggesting their potential use as novel growth regulators in plant tissue culture, but the molecular mechanism of their action is unclear. In this study, we compared the effects of SL-related inhibitors (TIS108 and KK094) and CKs (2iP, tZ, and kinetin) on adventitious shoot formation in ipecac. Exogenously applied SL-related inhibitors and CKs stimulated adventitious shoot formation. Combinations of SL-related inhibitors and kinetin also promoted adventitious shoot formation, but without additive effects. We also analyzed the expression of CK biosynthesis genes in ipecac. TIS108 increased the expression of the ipecac homolog of ISOPENTENYL TRANSFERASE 3 (CiIPT3) but decreased that of LONELY GUY 7 homolog (CiLOG7), presumably resulting in no change in 2iP-type CK levels. KK094 and kinetin increased CiLOG7 expression, elevating 2iP-type CK levels. Among pluripotency- and meristem-related genes, TIS108, KK094, and kinetin consistently increased the expression of ENHANCER OF SHOOT REGENERATION 2 homolog (CiESR2), which has a key role in shoot regeneration, in the internodal segment region that formed adventitious shoots. We propose that CiESR2 might be a key stimulator of adventitious shoot formation in ipecac.

Exogenous Kinetin Modulates ROS Homeostasis to Affect Heat Tolerance in Rice Seedlings.

Heat stress caused by rapidly changing climate warming has become a serious threat to crop growth worldwide. Exogenous cytokinin (CK) kinetin (KT) has been shown to have positive effects in improving salt and drought tolerance in plants. However, the mechanism of KT in heat tolerance in rice is poorly understood. Here, we found that exogenously adequate application of KT improved the heat stress tolerance of rice seedlings, with the best effect observed when the application concentration was 10-9 M. In addition, exogenous application of 10-9 M KT promoted the expression of CK-responsive OsRR genes, reduced membrane damage and reactive oxygen species (ROS) accumulation in rice, and increased the activity of antioxidant enzymes. Meanwhile, exogenous 10-9 M KT treatment significantly enhanced the expression of antioxidant enzymes, heat activation, and defense-related genes. In conclusion, exogenous KT treatment regulates heat tolerance in rice seedlings by modulating the dynamic balance of ROS in plants under heat stress.

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.

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.

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.

Cytoprotective activities of kinetin purine isosteres.

Kinetin (N6-furfuryladenine), a plant growth substance of the cytokinin family, has been shown to modulate aging and various age-related conditions in animal models. Here we report the synthesis of kinetin isosteres with the purine ring replaced by other bicyclic heterocycles, and the biological evaluation of their activity in several in vitro models related to neurodegenerative diseases. Our findings indicate that kinetin isosteres protect Friedreich́s ataxia patient-derived fibroblasts against glutathione depletion, protect neuron-like SH-SY5Y cells from glutamate-induced oxidative damage, and correct aberrant splicing of the ELP1 gene in fibroblasts derived from a familial dysautonomia patient. Although the mechanism of action of kinetin derivatives remains unclear, our data suggest that the cytoprotective activity of some purine isosteres is mediated by their ability to reduce oxidative stress. Further, the studies of permeation across artificial membrane and model gut and blood-brain barriers indicate that the compounds are orally available and can reach central nervous system. Overall, our data demonstrate that isosteric replacement of the kinetin purine scaffold is a fruitful strategy for improving known biological activities of kinetin and discovering novel therapeutic opportunities.

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.

Modulatory and Toxicological Perspectives on the Effects of the Small Molecule Kinetin.

Plant hormones are small regulatory molecules that exert pharmacological actions in mammalian cells such as anti-oxidative and pro-metabolic effects. Kinetin belongs to the group of plant hormones cytokinin and has been associated with modulatory functions in mammalian cells. The mammalian adenosine receptor (A2a-R) is known to modulate multiple physiological responses in animal cells. Here, we describe that kinetin binds to the adenosine receptor (A2a-R) through the Asn253 residue in an adenosine dependent manner. To harness the beneficial effects of kinetin for future human use, we assess its acute toxicity by analyzing different biochemical and histological markers in rats. Kinetin at a dose below 1 mg/kg had no adverse effects on the serum level of glucose or on the activity of serum alanine transaminase (ALT) or aspartate aminotransferase (AST) enzymes in the kinetin treated rats. Whereas, creatinine levels increased after a kinetin treatment at a dose of 0.5 mg/kg. Furthermore, 5 mg/kg treated kinetin rats showed normal renal corpuscles, but a mild degeneration was observed in the renal glomeruli and renal tubules, as well as few degenerated hepatocytes were also observed in the liver. Kinetin doses below 5 mg/kg did not show any localized toxicity in the liver and kidney tissues. In addition to unraveling the binding interaction between kinetin and A2a-R, our findings suggest safe dose limits for the future use of kinetin as a therapeutic and modulatory agent against various pathophysiological conditions.

Circumventing the Crabtree effect: forcing oxidative phosphorylation (OXPHOS) via galactose medium increases sensitivity of HepG2 cells to the purine derivative kinetin riboside.

Small-molecule compound-based therapies have provided new insights into cancer treatment against mitochondrial impairment. N6-furfuryladenosine (kinetin riboside, KR) is a purine derivative and an anticancer agent that selectively affects the molecular pathways crucial for cell growth and apoptosis by interfering with mitochondrial functions and thus might be a potential mitotoxicant. Metabolism of cancer cells is predominantly based on the Crabtree effect that relies on glucose-induced inhibition of cell respiration and thus on oxidative phosphorylation (OXPHOS), which supports the survival of cancer cells in metabolic stress conditions. The simplest way to circumvent this phenomenon is to replace glucose with galactose in the culture environment. Consequently, cells become more sensitive to mitochondrial perturbations caused by mitotoxicants. In the present study, we evaluated several cellular parameters and investigated the effect of KR on mitochondrial functions in HepG2 cells forced to rely mainly on OXPHOS. We showed that KR in the galactose environment is a more potent apoptosis-inducing agent. KR decreases the mitochondrial membrane potential, reduces glutathione level, depletes cellular ATP, and induces reactive oxygen species (ROS) production in the OXPHOS state, leading to the loss of cell viability. Taken together, these results demonstrate that KR directly acts on the mitochondria to limit their function and that the sensitivity of cells is dependent on their ability to cope with energetic stress.

Synergistic effect of cytokinin and gibberellins stimulates release of dormancy in tea (Camellia sinensis (L.) O. Kuntze) bud.

Reactivation of dormant meristem in banjhi (dormant) shoots is important to enhance the quality and quantity of tea production. The field grown tea bushes were subjected to treatment with dormancy breaking agents such as potassium nitrate (KNO3), thiourea, sodium nitro prusside (SNP), the phytohormones kinetin (Kn) and gibberellins (GA). The efficacy of Kn and GA were comparatively lesser than KNO3 while the combination of Kn and GA (50 and100 ppm respectively) resulted in better dormancy reduction in tea buds. This observation was supported by our results from gene expression study where accumulation patterns of mRNAs corresponding to histones (H2A, H2B, H3 and H4), cyclins (B2, D1 and D3), cyclin-dependent kinase (CDKA), ubiquitination enzymes (FUS, EXT CE2), cyclophilin, E2F, and tubulin were analyzed during growth-dormancy cycles in tea apical buds under the influence of Kn, GA and their combinations. The level of these mRNAs was low in dormant buds, which was significantly increased by foliar application of GA and Kn combination. The present study indicated that the foliar application of GA in combination with Kn will help to improve quality and quantity of tea production by breaking dormancy and stimulating the bud growth.

Anion exchange resins in phosphate form as versatile carriers for the reactions catalyzed by nucleoside phosphorylases.

In the present work, we suggested anion exchange resins in the phosphate form as a source of phosphate, one of the substrates of the phosphorolysis of uridine, thymidine, and 1-(ß-ᴅ-arabinofuranosyl)uracil (Ara-U) catalyzed by recombinant E. coli uridine (UP) and thymidine (TP) phosphorylases. α-ᴅ-Pentofuranose-1-phosphates (PF-1Pis) obtained by phosphorolysis were used in the enzymatic synthesis of nucleosides. It was found that phosphorolysis of uridine, thymidine, and Ara-U in the presence of Dowex® 1X8 (phosphate; Dowex-nPi) proceeded smoothly in the presence of magnesium cations in water at 20-50 °C for 54-96 h giving rise to quantitative formation of the corresponding pyrimidine bases and PF-1Pis. The resulting PF-1Pis can be used in three routes: (1) preparation of barium salts of PF-1Pis, (2) synthesis of nucleosides by reacting the crude PF-1Pi with an heterocyclic base, and (3) synthesis of nucleosides by reacting the ionically bound PF-1Pi to the resin with an heterocyclic base. These three approaches were tested in the synthesis of nelarabine, kinetin riboside, and cladribine with good to excellent yields (52-93%).

Natural plant hormones cytokinins increase stress resistance and longevity of Caenorhabditis elegans.

Cytokinins are phytohormones that are involved in many processes in plants, including growth, differentiation and leaf senescence. However, they also have various activities in animals. For example, kinetin and trans-zeatin can reduce levels of several aging markers in human fibroblasts. Kinetin can also protect mice against oxidative and glyoxidative stress, and prolong fruit flies' lifespan. Additionally, several cytokinins are currently used in cosmetics. To extend knowledge of the breadth of cytokinins' activities, we examined effects of natural cytokinin bases on the model nematode Caenorhabditis elegans. We found that kinetin, para-topolin and meta-topolin prolonged the lifespan of C. elegans. Kinetin also protected the organism against oxidative and heat stress. Furthermore, our results suggest that presence of reactive oxygen species, but not DAF-16 (the main effector of the insulin/insulin-like growth factor signaling pathway), is required for the beneficial effects of kinetin. Ultra-high performance liquid chromatography-tandem mass spectrometric analysis showed that kinetin is unlikely to occur naturally in C. elegans, but the worm efficiently absorbs and metabolizes it into kinetin riboside and kinetin riboside-5'-monophosphate.

Effects of kinetin on plant growth and chloroplast ultrastructure of two Pteris species under arsenate stress.

Cytokinins (CTKs) are effective in alleviating abiotic stresses on plants, but little information is available regarding the effects of CTKs on arsenic (As) accumulation and changes of chloroplast ultrastructure in plants with different As-accumulating ability. Here a hydroponic experiment was designed to evaluate the effects of different concentration of kinetin (KT, 0-40 mg/L) on growth and chloroplast ultrastructure of As hyperaccumulator Pteris cretica var. nervosa and non-hyperaccumulator Pteris ensiformis treated by 5 mg/L arsenate for 14 days. The growth parameters, As accumulation, contents of photosynthetic pigments and chloroplast ultrastructure were examined. The results showed that KT promoted the growth of two plants, and significantly increased As accumulation and translocation in P. cretica var. nervosa and P. ensiformis at 5 and 20 mg/L, respectively. Additionally, the contents of chlorophyll a and carotenoid in two plants showed no significant difference at 20 mg/L KT compared to the control. Chloroplast ultrastructure of P. cretica var. nervosa was integral with KT application. Comparatively, the swollen chloroplasts were increased, plasmolysis appeared, and chloroplast grana slice layers and stroma lamellas were clearly separated or distorted at 5 mg/L KT in P. ensiformis. The length and width of chloroplasts in P. cretica var. nervosa were significantly increased with KT addition compared to the control. However, the length of chloroplasts in P. ensiformis was significantly decreased but their width showed no significant change. Furthermore, the deterioration of chloroplast ultrastructure in P. ensiformis was ameliorated by 40 mg/L KT. These results suggested that KT increased As accumulation and was beneficial to maintain the photosynthetic pigments for a good growth of plants. Therefore, KT could maintain and reorganize the ultrastructure integrality of As-stressed chloroplasts to some extent for the two plants, especially at high concentration.

Kinetin alleviates chromium toxicity on growth and PS II photochemistry in Nostoc muscorum by regulating antioxidant system.

The present study was undertaken to evaluate the metal toxicity alleviating effects of kinetin (KN, 10 nM) on growth, photosynthetic pigments and photochemistry of PS II in the cyanobacterium Nostoc muscorum exposed to chromium (CrVI) stress (100 and 150 µM). Chromium declined growth, photosynthetic pigments (chlorophyll a, phycocyanin and carotenoids), photosynthetic oxygen evolution rate and parameters of fluorescence kinetics (ϕP0, FV/F0, ϕE0, Ψ0 and PIABS except F0/FV) in concentration dependent manner, while stimulating effects on respiration, energy flux parameters (ABS/RC, TR0/RC, ET0/RC and DI0/RC), oxidative stress biomarkers i.e., superoxide radical (SOR), hydrogen peroxide (H2O2) and lipid peroxidation (TBARS contents) and antioxidative enzymes: superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and glutathione-S-transferase (GST), were observed. However, upon addition of KN in the growth medium an alleviating effect against chromium induced toxicity on growth, photosynthetic pigments and photochemistry of PS II was recorded. This had occurred due to substantial reduction in levels of oxidative stress biomarkers: SOR, H2O2 and TBARS contents with concomitant rise in activity of antioxidative enzymes: SOD, POD, CAT and GST and appreciable lowering in the cellular accumulation of chromium. The overall results demonstrate that KN application significantly alleviated chromium induced toxicity on growth performance of the cyanobacterium N. muscorum due to significant improvement in photosynthetic pigments and photochemistry of PS II by up-regulating the activity of antioxidative enzymes, and declining cellular accumulation of chromium. Furthermore, Cr induced toxicity at lower dose (100 µM) was found to be ameliorated more efficiently in N. muscorum following supplementation of KN.

Kinetin improves motility, viability and antioxidative parameters of ram semen during storage at refrigerator temperature.

The present experiment was conducted to evaluate the effect of kinetin on ram semen quality during cold storage. Ejaculates were collected using an artificial vagina from five Qezel rams. Ejaculates which met the criteria (volume of 0.75-2 ml; minimum spermatozoa concentration of 2.5 × 109 spermatozoa/ml and forward progressive motility of 80%), were pooled, diluted with extender without kinetin (control) or enriched with 25 (K 25), 50 (K 50), 100 (K 100) and 200 (K 200) µM kinetin at a final concentration of 500 × 106 spermatozoa per mL. Spermatozoa motion characteristics were evaluated by computer-assisted sperm analysis. In addition, percent of viability (spermatozoa showing no color was considered to be alive) and spermatozoa with intact plasma membrane (spermatozoa with curled/swollen tail was considered healthy) were determined. Moreover, amounts of malondialdehyde (MDA), total antioxidant activity (AOA), nitric oxide (NO) and superoxide dismutase (SOD) activity were determined in the seminal plasma and spermatozoa at 0, 24, 48 and 72 h of storage. Higher percent of total and forward progressive motility was observed in K 25, K 50 and K 100 groups compared to control group at 72 h of storage (P < 0.001). Moreover, K 25 (78.61 ± 1.11%), K 50 (82.46 ± 1.08%) and K 100 (82.96 ± 1.49%) groups showed higher percentage of viability compared to control (72.38 ± 1.49%) at 72 h of storage (P < 0.05). Semen enrichment with kinetin resulted in the higher percent of intact plasma membrane of spermatozoa at 48 and 72 h (P < 0.001). Amounts of MDA were lower and amounts of AOA were higher in K 50 and K 100 groups compared to control at 48 and 72 h (P < 0.05). There were no significant differences in NO levels and SOD activities of seminal plasma and spermatozoa among groups during the experiment. The present experiment revealed that kinetin at proper concentration could enhances spermatozoa kinematics, viability, spermatozoa plasma membrane functionality and amounts of AOA and reduces the level of lipid peroxidation during chilled storage of ram semen.

Adenine type and diphenyl urea derived cytokinins improve the postharvest performance of Iris germanica L. cut scapes.

An experiment was designed to evaluate the effect of various adenine derived cytokinins (kinetin and 6-benzylaminopurine) and diphenyl urea cytokinin (thidiazuron) on the postharvest performance of cut scapes of Iris germanica. Flower scapes were harvested with the oldest bud at '1 day before anthesis stage', brought to laboratory under water, cut to a uniform length of 35 cm, divided into three sets viz., kinetin (KIN), 6-benzyl aminopurine (BAP) and thidiazuron (TDZ). Each set of scapes was treated with a particular cytokinin alone or in combination with 0.1 M sucrose. TDZ was effective than KIN and BAP in improving the postharvest life of the I. germanica scapes by 5.4 days as compared to the control (untreated scapes held in distilled water). This was because of the minimum percentage of bud abortion by TDZ application. Cytokinin application resulted in increased antioxidant activity, higher protein and phenolic content, besides a decrease in specific protease activity and α-amino acids in the tepal tissues. Application of TDZ resulted in the maximum increase in the superoxide dismutase, catalase and ascorbate peroxidase activity in the tepal tissues. The scapes treated with BAP and KIN maintained higher carbohydrate content in the tissue samples as compared to control and TDZ treated scapes. TDZ and BAP application resulted in increased membrane stability because of the decreased lipoxygenase activity which prevented membrane lipid peroxidation. Among the cytokinins tested, TDZ proved to be the promising cytokinin in improving the postharvest performance of beautiful flowers of I. germanica scapes.

Protecting the photosynthetic performance of snap bean under free air ozone exposure.

Tropospheric ozone (O3) is a major air pollutant and causes serious injury to vegetation. To protect sensitive plants from O3 damage, several agrochemicals have been assessed, including cytokinin (e.g., kinetin, KIN) and ethylenediurea (EDU) with cytokinin-like activity. In higher plant, leaves are primarily injured by O3 and protective agrochemicals are often applied by leaf spraying. To our knowledge, the mitigating abilities of EDU and KIN have not been compared directly in a realistic setup. In the present research, impacts of elevated O3 (2× ambient O3, 24hr per day, for 8days) on an O3 sensitive line (S156) of snap bean (Phaseolus vulgaris), which is often used for biomonitoring O3 pollution, were studied in a free air controlled exposure system. The day before starting the O3 exposure, plants were sprayed with a solution of EDU (300ppm), KIN (1mmol/L) or distilled water, to compare their protective abilities. The results demonstrated that 2× ambient O3 inhibited net photosynthetic rate and stomatal conductance, increased the minimal fluorescence yield of the dark-adapted state, decreased the maximal quantum yield of PSII photochemistry, and led to visible injury. KIN and EDU alleviated the reduction of the photosynthetic performance, and visible injury under O3 fumigation. The plants sprayed with EDU showed greater ability to mitigate the O3 damage than those sprayed with KIN. Chlorophyll fluorescence imaging may have detected more precisely the differences in O3 response across the leaf than the conventional fluorometer.