Benzyladenine Treatment Research Articles

The interface between the cell cycle and plant growth regulators: a mini review

The aim was to review knowledge about the interface betweenplant growth regulators and molecular checkpoints of the cell cycle. Atwhat level of biochemical regulation of the cell cycle do plant growthregulators interface? Are there different levels of interfacingdependent on the plant growth regulator involved? As a preamble totackling these questions, we overview the eukaryotic cell cycle withparticular emphasis on checkpoints that regulate the transition fromG0-G1-S-phase and G2-M. Cytokinins feature strongly as activators ofcell division in plants both in vivo and in vitro.Recent research has shown that zeatin treatment led to the up-regulationof CycD3 in Arabidopsis. This is a D-type cyclin showing stronghomology with vertebrate D cyclins which themselves are up-regulated byextracellular growth factors. Benzyladenine treatment can also shortenthe duration of S-phase through recruitment of latent origins of DNAreplication. Kinetin is involved in the phosphoregulation of the G2-Mcheckpoint; the major cyclin-dependent kinase (Cdk) at this checkpointhas recently been shown to be dephosphorylated as a result of cytokinintreatment, an effect which can also be mimicked by the fission yeastCdc25 phosphatase. Hence, a picture emerges of a cytokinin-inducedcontinuum of cell cycle activation through the up-regulation of a plantD-type cyclin at the G1 checkpoint and the phosphoregulation of the Cdkat the G2/M checkpoint. During S-phase, we argue for a link betweencytokinins and the proteins associated with replication origins.Gibberellic acid (GA) treatment induces internode elongation. Indeepwater rice, this response is mediated, at least partly, by aGA-induced up-regulation of a cyclin-Cdk at the G2-M checkpoint. Recentevidence has also linked abscisic acid to a cyclin-dependent kinaseinhibitor. These, so-called CKIs are negative regulators of Cdks whichfits with ABA's general role in growth inhibition; we await news ofethylene interactions. We highlight two instances of plant growthregulator-cell cycle interfacing during development, arguing for aninvolvement in microtubule orientation as a prerequisite to leafinitiation, and suggest a link between IAA and the activation of celldivisions in the pericycle required for lateral root initiation. A newD-type cyclin, recently discovered in Arabidopsis, may have akey role in this process. Finally, a model is presented which features ageneralised cyclin-Cdk checkpoint exhibiting various interfaces with theplant growth regulators.

The requirements for Ca 2+, protein phosphorylation and concurrent protein synthesis for zeatin signaling of acidic chitinase transcript accumulation in Cucumis sativus L.

We have previously reported that both Ca2+ and staurosporine-sensitive protein kinase(s) are involved in the cytokinin zeatin induction of cucumber chitinase activity and its protein content (Barwe et al. 2001). To further characterize signal transduction events involved in this cytokinin induction of chitinase gene expression, Northern hybridizations of total RNAs prepared from excised, dark-grown cucumber cotyledons treated with cytokinins and/or various agonists and antagonists of signal transduction components, were carried out using a cucumber acidic chitinase (CACHT) cDNA probe (Metraux et al. 1989). CACHT mRNA increased by approximately 5- to 6-fold in response to exogenous zeatin (Z), zeatin riboside (ZR), and benzyladenine (BA) treatment, but failed to accumulate in response to kinetin (K). Among the cytokinins tested, Z was most effective. The Z-induced accumulation of CACHT mRNA was inhibited by a plasma membrane Ca2+ channel blocker verapamil. Treatment of cotyledons with exogenous CaCl2 and calcium ionophore A23187 in the presence and absence of cytokinin enhanced CACHT mRNA accumulation. These two observations suggest the participation of extracellular calcium in signaling Z-induction. Furthermore, the presence of staurosporine (an inhibitor of protein kinase) in Z treatment reduced CACHT mRNA, suggesting the involvement of phosphorylation of one or more cellular proteins. In addition, we provide evidence that the Z-induction of CACHT mRNA is blocked by protein synthesis inhibitor cycloheximide treatment. Taken together, these results suggest that Ca2+ influx from extracellular space, protein phosphorylation, and concurrent protein synthesis events participate in cytokinin signaling during Z-induced CACHT transcript accumulation.

Foliar application of benzyladenine (BA) as a means to enhance shoot production for asexual propagation of young jack pine ( Pinus banksiana Lamb.) seedlings

Foliar applications of benzyladenine (BA) wereinvestigated as a potential means forenhancing development of proliferated dwarfshoot (pds), which may serve as stem cuttingmaterial for asexual propagation of young jackpine seedlings. BA application in combinationwith pruning promoted pds production. Potential production of 30–40 shoots per BAtreated plant were obtained within 6 monthsfrom sowing of seed, compared to 14–17 forpruned controls (no BA application) in thesame time period. The BA treatment thatresulted in the highest number of pds variedwith the frequency of BA application. Higherconcentrations of BA generally resulted ingreater numbers of pds. Increasing BAconcentration and frequency of applicationreduced rooting capacity of cuttings as wellas lengths of pds. The optimal BA treatmentsfor both total pds production and high rootingwas found to be BA applied singly at 62.5 or125 mg/l or applied twice at 31.2 or62.5 mg/l. The potential utilization of BAtreatments in operational asexual propagationprocedures of jack pine is discussed.

302 Comparative Effectiveness of Cytokinins on Quality of Soybean Sprouts

Soybean sprouts are one of the most-favored traditional vegetables around the world. The sprouts are usually consumed 7 to 10 days after sowing depending upon the growing conditions. High-quality sprouts should have less secondary roots, short and well-swollen hypocotyls in pure white color, and small cotyledons in hooked position. Cytokinins were reported to be effective in producing such sprouts by promoting sprout growth while inhibiting the excessive hypocotyl elongation and secondary root growth. Seeds of four soybean cultivars with different characteristics were soaked in water for 4 h and, 2 to 3 h after the imbibition, the seeds were soaked again in solutions of different cytokinins such as benzyladenine (BA), BA-riboside (BAR), BPA, 2iP, 2iP-riboside, 4-CPPU, and kinetin-riboside (KR) for 10 min. After the treatment, the sprouts were grown in a plastic tube (25 cm height × 10.5 cm diameter) a dark culture room with ample watering every 4 h. After 7 days of growth, uniform samples were taken from each treatment and the sprout characteristics were examined. Some cytokinins such as BA, BAR, 4-CPPU were highly effective in promoting the sprout growth (fresh weight) even though the hypocotyl length was markedly reduced. Other cytokinins such as 2iP, 2iPR, and KR had no effect on sprout growth. Hypocotyl diameter was markedly increased by BA and 4-CPPU treatment, thus resulting in short, strong and good quality sprouts. Cultivars responded differently to cytokinin treatment by showing different growth promotion depending upon the sprout parts. Injury-like symptoms, abnormal and twisted heads or cotyledons, appeared in cytokinin-treated sprouts at high concentrations and the symptoms were severe when the sprouts were grown at high temperatures. In all the cultivars tested, BAR appeared to be better than others in terms of sprout quality and growth promoting characteristics.

Benzyladenine as A Chemical Thinner for `McIntosh' Apples. I. Fruit Thinning Effect1s and Associated Relationships with Photosynthesis, Assimilate Translocation, and Nonstructural Carbohydrates

BA was applied at 50 or 100 mg·L-1 to `More-Spur McIntosh'/Malling 7 (M.7) apple trees [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] at the 10 mm stage of fruit development. BA thinned fruit and increased fruit size. There were two distinguishable peaks of fruit abscission during `June drop'. BA accentuated the naturally occurring waves of fruit abscission, and enhanced translocation of 14C-sorbitol from leaves to fruit when applied directly to the fruit, but not when applied directly to the leaves. Net photosynthesis was decreased and dark respiration was increased when temperature following BA application was high (30 °C), whereas there was no effect when temperature was lower (20 °C). Total nonstructural carbohydrates, total soluble sugars, and starch in the leaves decreased dramatically over the 12- or 13-day observation period, regardless of BA treatment. These carbohydrate concentrations in the leaves were lowered further by BA application. Abscising fruit, based on specific reddening of the pedicel, had higher carbohydrate levels than persisting fruit, regardless of BA application. We conclude that BA thins fruit, at least in part, by increasing dark respiration and decreasing net photosynthesis. Chemical name used: N-(phenylmethyl)-1H-purine-6-amine [benzyladenine (BA)].

The agrobacterium tumefaciens C58-6b gene confers resistance to N(6)-benzyladenine without modifying cytokinin metabolism in tobacco seedlings

The 6b gene of Agrobacterium tumefaciens has been demonstrated to modify the activity of the plant growth regulators, auxin and cytokinin. To study the possible mode of action of the gene, tobacco (Nicotiana tabacum L. cv. Samsun) plants were transformed with the A. tumefaciens C58-6b gene. Seeds obtained from morphologically normal transgenic as well as wild-type plants were germinated on media supplemented with growth-inhibitory levels of cytokinin, N(6)-benzyladenine (BA). The transgenic seedlings showed increased resistance to cytokinins, as reflected by continuous shoot development, whereas further growth of the wild-type plants beyond the cotyledonary stage was inhibited. Concurrently, the levels of 6b gene transcripts in transgenic seedlings increased greatly upon BA treatment. Since glucosylation of BA represents the main inactivation mechanism of the hormone, we analyzed BA glucoside formation during the early stages of seedling growth. Intracellular levels of the major BA metabolite, N(6)-benzyladenine-7-glucoside (80-92%), as well as other BA-derived components were found to be comparable in transgenic and wild-type seedlings. Therefore, increased resistance of the C58-6b transgenic seedlings to cytokinins could not be directly attributed to enhanced BA glucosylation and subsequent hormone inactivation.

Secondary Metabolites in Transformed Root Cultures of Campanula glomerata

Summary The transformed roots of Campanula glomerata L. var. dahurica Fish., induced by infection with Agrobacterium rhizogenes MAFF 03-01724, produced the anthocyanins cyanidin 3-glucoside and cyanidin 3-rutinoside, a flavonoid rutin and a phenylpropanoid glucoside coniferin, together with the polyacetylene constituents lobetyol, lobetyolin and lobetyolinin. Although illumination was inhibiting for root proliferation, it was an essential factor for the accumulation of anthocyanin and flavonoid in the tissues. Addition of benzyladenine (BA) to the medium also promoted the accumulation of phenolics (anthocyanins, rutin and coniferin) in the roots. Polyacetylene production in the roots was not greatly affected by either illumination or BA treatment.

Sequential BA Applications Enhance Offset Formation in Hosta

A study conducted in 1995 and repeated in 1996 determined the effects of repeated BA applications and subsequent repeated removals on yields of offsets in Hosta Tratt. (Funkia K. Spreng; Niobe Salisb.) stock plants. Two hosta cultivars, `Francee' and `Francis Williams', received zero, one, two, three, or four foliar applications of benzyladenine (BA) at 3000 mg·L-1. Plants receiving multiple applications were retreated at 30-day intervals following offset removal from all plants. A single BA application stimulated offset formation in both cultivars in both years, but repeated applications were necessary for a continued response following offset removal. Total offset yield increased linearly as the number of BA applications increased. At 120 days after the first treatment in 1995, `Francee' plants receiving four applications had produced an average of 22 offsets, and `Francis Williams' plants 18 offsets, whereas control plants produced 9.8 and 0 offsets, respectively. Similar data for 1996 were 31.2 offsets for `Francee' and 22.4 offsets for `Francis Williams,' whereas control plants produced 6.8 and 2.6 offsets, respectively. Offset stage of development, as indicated by leaf number, and growth index generally were not affected by BA treatment. No phytotoxicity was observed, and plant appearance was enhanced due to the outgrowth of BA-stimulated lateral buds. Chemical name used: N-(phenylmethyl)-1H-purin-6-amine (benzyladenine, BA).

Cytokinin and Auxin Sprays Affect the Incidence of Poinsettia Bract Necrosis

In 1996, `Supjibi red' poinsettias were sprayed at initial anthesis with the cytokinin benzyladenine (BA) (10 or 100 ppm), or with the cytokinin analogs CPPU or thidiazuron (1 or 10 ppm), or with Accel (10 or 100 ppm BA)—a 10:1 mixture of BA and gibberellin. A spray of thidiazuron at 1 or 10 ppm, Accel at 10 or 100 ppm, or BA at 100 ppm suppressed the incidence of necrosis relative to untreated plants. However, cytokinin treatments tended to induce the expansion of young bracts and fading of bract color. In a separate 1996 study, plants were sprayed with 100 ppm BA at 2-week intervals between visible bud and initial anthesis; and in 1997, 20 ppm of the auxin indole-3-butyric acid (IBA) was applied at similar intervals. The later in bract development that BA was applied, the lower the incidence of necrosis observed at 6 weeks after anthesis. In contrast to BA treatment effects, necrosis was highest with late IBA applications (when observed 3 weeks after anthesis). Late sprays of IBA induced bract epinasty. A 1:1 mixture of BA plus IBA applied at initial anthesis at 25 or 50 ppm BA, suppressed bract necrosis without causing adverse side effects.

Effect of Benzuladenine on Apple Fruit Thinning and Its Mode of Action

Benzyladenine (BA) applied at the 10-mm stage at 50 and 100 mg·L-1 thinned fruit, increased fruit size, and caused seed abortion. The translocation of 14C-sorbitol from leaves to fruit was promoted by B A application to the fruit, but not when BA was applied to the leaves. Therefore, it is unlikely that BA causes thinning directly by restricting photosynthate movement into the fruit. Net photosynthesis was decreased and dark respiration was increased when temperature following BA application was high (30 °C), whereas there was no effect when temperature was lower (20 °C). The seed number in abscising fruit was greater in BA-treated fruit than in control fruit. The number of viable seeds in BA-treated fruit was reduced. Tipping the bourse shoot increased fruit set, regardless of BA treatment. Benzyladenine thinned fruit when only one leaf was on the girdled fruiting spur, but not when leaf number was greater than two. Reduction of carbohydrates available for fruit appears to be the primary factor responsible for the thinning induced by BA. E-mail Yuan@pssci.umass.edu

Differential expression of the arabidopsis nia1 and nia2 genes. cytokinin-induced nitrate reductase activity is correlated with increased nia1 transcription and mrna levels

Nitrate reductase (NR) activity increased up to 14-fold in response to treatment of Arabidopsis thaliana seedlings with the cytokinin benzyladenine. NR induction was observed in seedlings germinated directly on cytokinin-containing medium, seedlings transferred to cytokinin medium, and seedlings grown in soil in which cytokinin was applied directly to the leaves. About the same level of induction was seen in both wild-type and Nia2-deletion mutants, indicating that increased NR activity is related to the expression of the minor NR gene, Nia1. The steady-state Nia1 mRNA level was increased severalfold in both wild-type and mutant seedlings after benzyladenine treatment. Transcript levels of the Nia2 gene, which is responsible for 90% of the NR activity in developing wild-type seedlings, did not show any changes upon cytokinin treatment. Nuclear run-on assays demonstrated that Nia1 gene transcription increased dramatically after cytokinin treatment.

Propagation from cuttings of two woody ornamental Australian shrubs, Boronia megastigma Nees (brown boronia) and Hypocalymma angustifolium Endl. (white myrtle)

Summary. While many woody plant cuttings respond to propagation conditions in similar ways, results presented here indicate that some responses are species specific. Propagation of Boronia megastigma and Hypocalymma angustifolium cuttings was successful except when cuttings were struck without auxin treatment in a pinebark-based propagation medium. More stem H. angustifolium cuttings (100%) produced roots than terminal (shoot tip) cuttings (45.2%). Benzyladenine and gibberellic acid treatment of stock plants decreased endogenous starch concentration and propagation success of both species. Boronia megastigma cuttings propagated poorly when taken in winter when flowers were developing on stock plants. Conversely, adventitious rooting of H. angustifolium had greatest success when cuttings were taken in winter during flower development. Seasonal variation in propagation success may be mediated through changes in the endogenous plant growth regulator or carbohydrate concentrations.

Effect of Benzyladenine (BA) on Fruit Thinning and Carbohydrate Status in Apples

BA applied at the 10-mm stage at 50 and 100 ppm thinned, increased fruit size, and seed abortion. Net photosynthesis was decreased and dark respiration was increased when temperature following BA application was high (30°C), whereas there was no effect when temperature was lower (20°C). The seed number in abscising fruit was greater in BA-treated fruit than in control fruit. The number of viable seeds in BA-treated fruit was reduced. Tipping the bourse shoot increased fruit set, regardless of BA treatment. BA did not thin fruit with 25 leaves or greater. The translocation of 14C-sorbital from leaves to fruit was promoted by BA application to the fruit, but not when BA was applied to the leaves. The thinning induced by BA will be discussed in relation to available carbohydrate.

Benzyladenine-induced Offset Formation in Hosta Dependent on Cultivar

A foliar spray of 0, 1250, 2500, or 3750 mg benzyladenine (BA)/L was applied to 10 Hosta Tratt. (Funkia K. Spreng; Niobe Salisb.) cultivars. Response to BA treatment was cultivar dependent, with BA promoting offset formation in half of the cultivars. Compared to the control, increase in offsets produced by cultivars treated with 3750 mg BA/L ranged from 116% in `Francee' to 3500% in `Francis Williams' at 30 days after treatment (DAT) and from 150% in `Royal Standard' to 2250% in `Francis Williams' at 60 DAT. Offset stage of development, as indicated by the number of unfurled leaves, was also cultivar- and BA-dependent. All cultivars treated with 3750 mg BA/L had an average of three or more unfurled leaves at 60 DAT, while among control plants, 40% of cultivars averaged fewer than three unfurled leaves. No phytotoxic symptoms were noted in any cultivar, and plant size was either increased or not affected by BA treatment. Chemical name used: N-(phenylmethyl)-1H-purin-6-amine (benzyladenine; BA).

BA-INDUCED OFFSET FORMATION IN HOSTA DEPENDENT ON CULTIVAR

A foliar spray of 0, 1250, 2500, or 3750 mg benzyladenine (BA)/liter was applied to 10 hosta cultivars. Response to BA treatment was cultivar dependent, with BA promoting offset formation in half of the cultivars tested. Increase in offsets compared to the control ranged from 116% in `Francee' to 3500% in `Francis Williams' at 30 days after treatment (DAT) and from 150% in `Royal Standard' to 2250% in `Francis Williams' at 60 DAT with 3750 mg BA/liter. Stage of development, as indicated by the number of unfurled leaves on offsets, was also cultivar and BA dependent. All cultivars treated with 3750 mg BA/liter had an average of three or more unfurled leaves at 60 DAT, while among control plants, 40% of cultivars averaged less than three unfurled leaves. No phytotoxic symptoms were noted in any cultivar, and growth index was either increased or not affected by BA treatment. Chemical name used: N-(phenylmethyl)-1H-purin-6-amine (benzyladenine, BA).

ATTEMPTS TO OVERCOME THE BARRIER OF INTERSPECIFIC HYBRIDIZATION BETWEEN CUCUMIS MELO AND C. METULIFERUS

The crossability ofCucumis meloandC. metuliferuswas studied in order to find ways to effect the cross between the two species. In cross-pollination withinC. melo, the pollen tubes entered the ovarian cavity within 24 h, and fertilization occurred within 48 h. Pollen germinated well after cross-pollination between the species, but pollen tubes grew slowly.C. metuliferuspollen tubes were arrested in the stigma or the upper style ofC. meloflowers.The influence of 100-, 150-, and 200-krad gamma radiation on in vitro germination, pollen tube growth ofC. meloandC. metuliferus, and on in vivo fertilization ofC. melowas studied. Pollen ofC. metuliferusappeared to be much less sensitive to gamma rays than that ofC. melo.Higher radiation doses were found to reduce fruit set ofC. melo.Irradiation of pollen ofC. meloalways resulted in “pseudo-fertilization”.We attempted to overcome the prefertilization crossing barrier betweenC. meloandC. metuliferusby using techniques of bud pollination, benzyladenine (BA) treatment, and irradiated mentor pollen. Ten lines ofC. meloand 6 accessions ofC. metuliferuswere used as female and male parents, respectively. The techniques of BA and bud pollination were ineffective. Numerous fruits with few embryos were obtained on some of theC. melolines after using the irradiated mentor pollen technique. Embryos, which were isolated at the age of 20–25 days and cultured on medium consisting of 1/3 Murashige and Skoog medium, were observed to provide normal development. All nine surviving plants were similar to the maternal parent and were not interspecific hybrids.

Effect of Benzyladenine on Transpiration, Water Potential and its Components in Genotypes of Wheat Contrasting in Drought Tolerance

Drought tolerant and susceptible cultivars of wheat, C-306 and Kalyan sona, growing under non-stressed and water-stressed conditions, were sprayed with benzyladenine (BA) at 70 days after sowing (DAS). Observations recorded at 5, 10, 15, 20 and 25 days after spraying revealed that BA increased the rate of transpiration (TR) in C-306 under non-stressed conditions. However, under water stress, the increase was significant only after 5 days of BA spraying. In Kalyan sona BA treatment either decreased TR or did not exhibit significant increase under non-stressed conditions, but caused significant increase in TR under water stress. The increase in TR was elicited through enhanced stomatal opening. Water potential, osmotic potential and pressure potential of both genotypes decreased on account of water stress. The effect of BA was not perceptible on restoration of leaf water potential (LWP) or its components. The effect of BA was possibly confined to stomatal behaviour and transpiration.

Reduction of Postproduction Quality Loss in Potted Miniature Roses

Potted miniature roses (Rosa × hybrids L. `Belle Sunblaze') held after production in simulated home conditions (21C, continuous fluorescent light) yellowed prematurely, flower buds and leaves abscised, and flower buds failed to open. These symptoms were accelerated when the plants were exposed to low concentrations (1 μl·liter-1) of ethylene in the absence of inhibitors. Spray application of 100 μl BA/liter reduced leaf yellowing but had no significant effect on flower opening or bud abscission. Spray application of 1 mm silver thiosulfate (STS) strongly promoted flower display but did not prevent leaf yellowing. A combined BA and STS treatment greatly improved the postproduction quality of rose plants, particularly if applied 1 day before harvest. Chemical name used: benzyladenine (BA).

Manipulation of flowering and vegetative growth of Brown Boronia ( Boronia megastigma Nees.) and White Myrtle ( Hypocalymma angustifolium Endl.) using plant growth regulators

Plant growth regulators had a variety of effects on growth and flowering of Brown Boronia and White Myrtle. Morphactin, TIBA and benzyladenine stimulated lateral vegetative growth in warm conditions. Benzyladenine treatment of plants decreased the number of weeks of cool conditions (17°C day/9°C night) required to reach anthesis in both species, in Brown Boronia reducing the number of weeks required from 22 to 14. Paclobutrazol also decreased the number of weeks to anthesis in Brown Boronia and increased the percentage of axils with flowers. Paclobutrazol enabled White Myrtle plants to flower in an environment considered non-inductive for flowering. Many treatments that encouraged vigorous vegetative growth inhibited flowering in both species. The timing of growth regulator treatment in relation to flower evocation, and the environment in which the plants are growing can greatly influence the response of these species to plant growth regulator treatment.

Effect of triacontanol on the lipid composition of cotton (Gossypium hirsutum L.) leaves and its interaction with indole-3-acetic acid and benzyladenine

Application of triacontanol (TRIA), a long chain aliphatic alcohol (C-30), to cotton (Gossypium hirsutum L.) leaves resulted in an increase in dry weight and an alteration in lipid composition. A significant increase in monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) was attained 24 h after TRIA treatment. However, no significant change in any of the individual phospholipids was observed. Benzyladenine (BA) treatment increased only phosphatidylcholine (PC) levels without having any effect on either glycolipids or other phospholipids. Indole-3-acetic acid (IAA) initiated no significant change in the lipid composition. Combined treatment with TRIA and BA resulted in an increase of MGDG, DGDG and PC, indicating that the individual effects of these two growth regulators were not altered. The combined treatment of IAA and TRIA did not bring about any change in the levels of MGDG and DGDG indicating that the effect of TRIA was nullified by IAA. MDGD is known to be involved in the packaging of photosystem I proteins. Whether TRIA-induced increase in dry weight which is due to the enhanced photosynthetic rate, is related to increased MGDG levels is not yet discernible.