Showing papers on "Gibberellic acid published in 2007"

Salicylic acid inhibits gibberellin-induced alpha-amylase expression and seed germination via a pathway involving an abscisic-acid-inducible WRKY gene

Abstract: It is well known that abscisic acid (ABA) antagonizes gibberellin (GA)-promoted seed germination. Recent circumstantial evidence suggests that salicylic acid (SA) also inhibits seed germination in maize and Arabidopsis. Our study shows that SA blocks barley seed germination in a dosage dependent manner. As an initial effort to addressing the mechanism controlling the crosstalk of SA, GA and ABA signaling in barley, we studied the regulation of α-amylases by SA and a WRKY gene whose expression is modulated by these hormones. Assays of α-amylase activity reveal that GA-induced α-amylase production in aleurone cells is inhibited by bioactive SA, but not its analogs, 3-hydroxybenzoic acid and 4-hydroxybenzoic acid. This inhibitory effect is unlikely due to repressing α-amylase secretion or inhibiting α-amylase enzyme activities. Northern blot analyses indicate that SA suppresses GA-induced expression of a barley low pI α-amylase gene (Amy32b). Because our previous data indicate that ABA-inducible and GA-suppressible WRKY genes inhibit the expression of α-amylase genes in rice, we studied the steady state mRNA levels of a barley WRKY gene, HvWRKY38. The expression of HvWRKY38 in barley aleurone cells is down-regulated by GA, but up-regulated by SA and ABA. However, the regulation of HvWRKY38 by SA appears to be different from that of ABA in term of the kinetics and levels of induction. Over-expression of HvWRKY38 in aleurone cells by particle bombardment blocks GA induction of the Amy32b promoter reporter construct (Amy32b-GUS). Therefore, HvWRKY38 might serve as a converging node of SA and ABA signal pathways involved in suppressing GA-induced seed germination.

Cotton ghdreb1 increases plant tolerance to low temperature and is negatively regulated by gibberellic acid

Abstract: Summary • The transcription factors C-repeat binding factors/dehydration-responsive element binding proteins (CBFs/DREBs) control the expression of many stress-inducible genes in Arabidopsis. • A cDNA clone, designated GhDREB1, was isolated from cotton (Gossypium hirsutum) by cDNA library screening. • Northern blot analysis indicated that mRNA accumulation of GhDREB1 was induced by low temperatures and salt stress, but was not induced by abscisic acid (ABA) or drought stress in cotton seedlings. Transgenic tobacco (Nicotiana tabacum) plants overexpressing GhDREB1 displayed stronger chilling tolerance than wild-type plants. Their leaf chlorophyll fluorescence, net photosynthetic rate and proline concentrations were higher than those of control plants during low-temperature treatment. However, under normal growth conditions, the transgenic tobacco plants exhibited retarded growth and delayed flowering. Interestingly, GhDREB1 transcripts in cotton seedlings were negatively regulated by gibberellic acid (GA3) treatment. Analysis of the promoter of the GhDREB1 gene revealed the presence of one low-temperature and four gibberellin-responsive elements. Green fluorescent protein (GFP) signal intensity or β-glucuronidase (GUS) activity driven by the GhDREB1 promoter was clearly enhanced by low temperature but repressed by GA3. • These results suggest that GhDREB1 functions as a transcription factor and plays an important role in improving cold tolerance, and also affects plant growth and development via GA3.

Geranyl diphosphate synthase is required for biosynthesis of gibberellins

Abstract: Geranyl diphosphate synthase (GPS) is generally considered to be responsible for the biosynthesis of monoterpene precursors only. However, reduction of LeGPS expression in tomato (Lycopersicon esculentum) by virus-induced gene silencing resulted in severely dwarfed plants. Further analysis of these dwarfed plants revealed a decreased gibberellin content, whereas carotenoid and chlorophyll levels were unaltered. Accordingly, the phenotype could be rescued by application of gibberellic acid. The dwarfed phenotype was also obtained in Arabidopsis thaliana plants transformed with RNAi constructs of AtGPS. These results link geranyl diphosphate (GPP) to the gibberellin biosynthesis pathway. They also demand a re-evaluation of the role of GPS in precursor synthesis for other di-, tri-, tetra- and/or polyterpenes and their derivatives.

Effects of salt stress on mustard as affected by gibberellic acid application

Abstract: Summary. The effects of gibberellic acid (GA 3 ) on growth, physiology and yield of salt-stressed mustard (Brassica juncea L. Czern & Coss) cv. Varuna plants were studied. The stress imposed by 25 or 50 mM NaCl reduced substantially leaf area, dry mass, leaf chlorophyll content, stomatal conductance and net photosynthetic rate 50 days after emergence. At harvest, although other yield components were generally reduced, total seed protein content showed a significant increase. Furthermore, the response was more pronounced at the higher concentration NaCl (50 mM) applied. On the contrary, the application of 10 -5 M GA 3 appeared to mitigate the adverse effects of salinity stress on the overall performance and productivity of mustard.

Decreased shoot stature and grain α-amylase activity following ectopic expression of a gibberellin 2-oxidase gene in transgenic wheat

Abstract: Ectopic expression of a gibberellin 2-oxidase gene (PcGA2ox1) decreased the content of bioactive gibberellins (GAs) in transgenic wheat, producing a range of dwarf plants with different degrees of severity. In at least one case, a single transformation event gave rise to T(1) plants with different degrees of dwarfism, the phenotypes being stably inherited over at least four generations. The dwarf phenotype, which included dark-green leaves, increased tillering and, in severe cases, a prostrate growth habit, was replicated by the application of a GA biosynthesis inhibitor to the wild type. Ear rachis length, grain set, and grain size were also decreased in the wheat transformants, compared with an azygous (null) line. The extent of post-germination alpha-amylase production in grains reflected the severity of the shoot phenotype of the transformants and both developmental processes were restored to normal by the application of gibberellic acid (GA(3)). Expression of two GA biosynthesis genes (TaGA20ox1 and TaGA3ox2) was up-regulated, and that of two alpha-amylase gene families (alpha-Amy1 and alpha-Amy2) down regulated, in scutella of semi-dwarf lines, compared with controls. The marked decline in transcript abundance of both alpha-amylase gene families in aleurone was associated with a decreased content of bioactive GAs in grains of the semi-dwarf lines.

Mutation induced by ethylmethanesulphonate (EMS), in vitro screening for salt tolerance and plant regeneration of sweet potato ( Ipomoea batatas L.)

Abstract: Salt tolerant cultivars of sweet potato (Ipomoea batatas L.) can be obtained from induced mutation. The objective of the present study was to induce mutation for salt tolerance using ethylmethanesulphonate (EMS) in calli of sweet potato, followed by cell line selection and subsequent plant regeneration. Calli initiated from leaf explants were treated with 0.5% EMS for 0, 1, 1.5, 2, 2.5 and 3 h, followed by rinsing with sterile distilled water for four times. Preliminary experiments showed that 200 mM NaCl could be used as selection pressure. Salt tolerant calli were sub-cultured on medium supplemented with 200 mM NaCl for selection of mutant cell lines and this process repeated 5 times (20 days each). The selected calli were transferred onto somatic embryo formation medium, which was Murashige and Skoog (MS) medium supplemented with 4 mg l−1 abscisic acid (ABA), 10 mg l−1 gibberellic acid (GA). After 15 days, somatic embryos were transferred onto MS medium supplemented with 0.05 mg l−1 ABA, 0.2 mg l−1 zeatin (ZT) for regeneration. Plants designated as ML1, ML2 and ML3 were regenerated from the somatic embryos formed by calli treated with 0.5% EMS for 2 and 2.5 h. After propagation, salt tolerance of these mutants was investigated. Data suggested the mutants were more salt tolerant than control plants.

Influence of gibberellic acid on 14CO2 metabolism, growth, and production of alkaloids in Catharanthus roseus

Abstract: Changes in growth parameters, carbon assimilation efficiency, and utilization of 14CO2 assimilate into alkaloids in plant parts were investigated at whole plant level by treatment of Catharanthus roseus with gibberellic acid (GA). Application of GA (1 000 g m−3) resulted in changes in leaf morphology, increase in stem elongation, leaf and internode length, plant height, and decrease in biomass content. Phenotypic changes were accompanied by decrease in contents of chlorophylls and in photosynthetic capacity. GA application resulted in higher % of total alkaloids accumulated in leaf, stem, and root. GA treatment produced negative phenotypic response in total biomass production but positive response in content of total alkaloids in leaf, stem, and roots. 14C assimilate partitioning revealed that 14C distribution in leaf, stem, and root of treated plants was higher than in untreated and variations were observed in contents of metabolites as sugars, amino acids, and organic acids. Capacity to utilize current fixed 14C derived assimilates for alkaloid production was high in leaves but low in roots of treated plants despite higher content of 14C metabolites such as sugars, amino acids, and organic acids. In spite of higher availability of metabolites, their utilization into alkaloid production is low in GA-treated roots.

Dormancy-break and germination in seeds of Prunus campanulata (Rosaceae): role of covering layers and changes in concentration of abscisic acid and gibberellins

Abstract: Intact seeds (seed+endocarp) from freshly harvested fruits of Prunus campanulata were dormant, and required 4–6 weeks of warm followed by 8 weeks of cold stratification for maximum germination percentage. Removing both endocarp and seed coat, however, promoted germination in a high percentage of non-stratified seeds. Treatment of intact, non-stratified seeds with gibberellic acid (GA3) was only partially effective in breaking dormancy. However, GA3 promoted germination of non-stratified seeds in which the endocarp (but not the seed coat) had been removed. The order of abscisic acid (ABA) concentration in fresh seeds was endocarp > seed coat > embryo, and its concentration in endocarp plus seed coat was about 6.2-fold higher than that in the embryo. Total ABA contents of seeds subjected to warm and/or cold moist stratification were reduced 6- to 12-fold. A higher concentration of GA4 was detected in embryos of non-dormant than in those of dormant seeds. Fluridone, a carotenoid biosynthesis inhibitor, was efficient in breaking dormancy of Prunus seeds. Paclobutrazol, a GA biosynthesis inhibitor, completely inhibited seed germination, and the inhibitory effect could be partially reversed by GA4, but not by GA3. Thus, dormancy in P. campanulata seeds is imposed by the covering layers. Dormancy break is accompanied by a decrease in ABA content of the covering layers and germination by an increase of embryonic GA4 content.

Efficient method of micropropagation and in vitro rooting of teak (Tectona grandis L.) focusing on large-scale industrial plantations

Abstract: Multiple shoots of high quality were produced in vitro from nodal expiants of Tectona grandis. An average of about 4 shoots/uninodal expiant was obtained within 4 weeks of culture on Murashige and Skoog’s (mMS) medium modified by 50% reduction in NH4NO3 concentration, supplemented with benzylaminopurine (1.5 mg L−1); indole-3-butyric acid (0.01 mg L−1) and gibberellic acid (0.1 mg L−1). The latter was applied both in the medium and by soaking the nodal segments for 10 s. in a gibberellic acid solution of 100 mg L−1. Hundred percent of shoots rooted cultured on modified MS medium containing IBA (0.5 mg L−1) and putrescine (160 mg L−1). Putrescine promoted both strong and highly ramified roots and fast growing shoots during the rooting phase, conditioning the plantlets for a good survival and quality. Plantlets were transferred to jiffy pots for a short acclimatization stage in greenhouse where they survived at 100%. This highly reproducible procedure can be adopted for large scale teak propagation.

Changes in carbohydrate contents of Zantedeschia leaves under gibberellin-stimulated flowering

Abstract: The effect of gibberellic acid (GA3) on the carbohydrate accumulation in relation to vegetative growth of Zantedeschia ‘Black Magic’ plants undergoing transition to flowering was investigated. In response to GA treatment the carbohydrate level increased independently of earlier stimulation of shoot emergence. Under vegetative growth stage the content of reducing sugars of leaf blades was 2.5-fold higher than in control plants, and suggests the stimulation of photosynthetic activity. The changes observed during the flowering, in principle noted in petiole tissues, support the GA-effect on assimilate transport to the sink organs. Moreover, the high level of non-structural carbohydrates in petiole tissues, in particular reducing sugars, can be an effect of photosynthetic activity of these organs and/or essential for osmoregulation and high turgor pressure. The results indicate that apart from the influence on the shoot emergence, the GAs may stimulate the photosynthetic activity from the beginning of shoot growth and are thus responsible for the enhancement of callas flower yield.

Gibberellic acid (GA3) enhance seed water uptake, germination and early seedling growth in sugar beet under salt stress.

Abstract: The study was carried out to assess whether water uptake could be improved in sugar beet seeds and salt tolerance at the germination and early seedling stage by soaking the seeds for 10 h in distilled water (control), 100, 150 and 200 mg L(-1) GA3. Electrical Conductivity (EC) values of the NaCl solution were 0.0 (control), 4.7, 9.4 and 14.1 dS n(-1) NaCl. Priming increased the final germination percentage and the germination rate (1/t 50, where t 50 is the time to 50% of germination) under saline condition. Water uptake of primed seeds also increased significantly with increasing concentration of GA3 as compared to control. Priming also alleviated the adverse effect of salt stress on sugar beet in terms of roots and shoots lengths and fresh weights of plants, roots and shoots.

Effect of gibberellic acid on fruit cracking and quality of Bing and Sam sweet cherries

Abstract: Rain-induced cracking of sweet cherries (Prunus avium L.) is a major problem in many cherry growing regions throughout the world. One method to reduce cracking is to grow cracking resistant cultivars; however, no completely effective control measures are currently available to eliminate this problem. Studies conducted in New Zealand to test the ameliorating properties of gibberellic acid sprays to reduce cracking were examined. The results revealed that repeated or singular foliar applications at 10 or 40 mg L-1 gibberellic acid (GA3), respectively, increased both fruit cracking, and fruit firmness, but delayed fruit colour development. Key words: Prunus avium, cherry splitting, cracking

Somatic embryogenesis and plant regeneration in Catharanthus roseus

Abstract: Embryogenic callus in Catharanthus roseus was initiated from hypocotyl on Murashige and Skoog’s (MS) medium supplemented with 1.0–2.0 mg dm−3 of 2,4-dichlorophenoxyacetic acid (2,4-D) or chlorophenoxyacetic acid (CPA). Calli from other sources were non-embryogenic. Numerous somatic embryos were induced from primary callus on MS medium suplemented with naphthalene acetic acid (NAA) within two weeks of culture. Embryo proliferation was much faster on medium supplemented with 6-benzylaminopurine (BAP). After transfer to medium with gibberellic acid (GA3, 1.0 mg dm− 3) mature green embryos were developed and germinated well into plantlets on MS liquid medium supplemented with 0.5 mg dm−3 BAP. Later, embryos with cotyledonary leaves were subjected to different auxins treatments for the development of roots. Before transfer ex vitro, plantlets were cultivated on half strength MS medium containing 3 % sucrose and 0.5 mg dm−3 BAP for additional 2 weeks. Additionally, the effect of liquid medium has been evaluated at different morphogenetic stages.

The effect of gibberellic acid on the in vitro germination of coconut zygotic embryos and their conversion into plantlets

Abstract: The effect of gibberellic acid (GA3) was tested on germination of coconut zygotic embryos, their conversion into plantlets and ex vitro survival. There were four treatments consisting of 5 wk of culture in semi-solid medium or liquid medium, with or without GA3. Embryos were then transferred to GA3 free-liquid medium for the rest of a 32-wk culture. Germination and conversion percentages were higher in semi-solid medium than in liquid medium, and with both media percentages increased with GA3 treatment (with the exception of the highest GA3 concentration). Embryos of two varieties (MGD and MYD) were used. The following are the results with MGD embryos. Optimum GA3 concentration in liquid medium was 0.46 μM, with 80% germination (62% in the control without GA3) and 4.6 μM in semi-solid medium with 98% germination (71% in the control). With GA3 treatment, germination was also faster. Conversion in semi-solid medium with GA3 was 87% (60% in the control), and 45% in liquid medium with GA3 (25% in the control). Once the plantlets had at least three bifid leaves and three primary roots at the time of transfer to ex vitro, they survived independently of the treatment. When MYD embryos were used, germination and conversion percentages were higher in semi-solid medium than in liquid medium, and they increased when GA3 was used, although percentages were lower than those obtained with MGD embryos. The results showed that the use of GA3 benefited coconut embryos in culture because it favored germination and conversion to plants on semi-solid medium, and hence improved previous protocols.

Effects of gibberellic acid and prohexadione-calcium on growth, chlorophyll fluorescence and quality of okra plant

Abstract: The experiment was conducted to identify the response of three cultivars of okra [Abelmoschus esculentus (L.) Moench] to exogenous hormones [gibberellic acid-(GA3) and prohexadione-Ca] applied as foliar spray. Stem and leaf dry masses and stem length were significantly enhanced by the application of exogenous GA3, but prohexadione-Ca inhibited growth. Control and prohexadione-Ca treated okra plants took more time to bloom than did GA3 treated plants. In the fruits of all the cultivars a decrease in fructose content was observed, while protein content remained almost unchanged after the application of the two growth regulators. The small changes in chlorophyll a fluorescence characteristics observed under prohexadione-Ca suggested a weakening of the photochemical processes near the photosystem 2 reaction centre. The lowering of ratio between maximum time to reach maximum fluorescence, Fm (Tmax) and Area (sum of Fm-Ft for t = 0 to t = Tmax) caused by GA3 was probably due to the increase of Area rather than to changes in Tmax.

Disrupting Abscisic Acid Homeostasis in Western White Pine (Pinus monticola Dougl. Ex D. Don) Seeds Induces Dormancy Termination and Changes in Abscisic Acid Catabolites

Abstract: To investigate the role of abscisic acid (ABA) biosynthesis and catabolism in dormant imbibed seeds of western white pine (Pinus monticola), ABA and selected catabolites were measured during a combined treatment of the ABA biosynthesis inhibitor fluridone, and gibberellic acid (GA). Fluridone in combination with GA effectively disrupted ABA homeostasis and replaced the approximately 90-day moist chilling period normally required to break dormancy in this species. Individually, both fluridone and GA treatments decreased ABA levels in the embryos and megagametophytes of white pine seeds compared to a water control; however, combined fluridone/GA treatment, the only treatment to terminate dormancy effectively, led to the greatest decline in ABA content. Fluridone treatments revealed that a high degree of ABA turnover/transport occurred in western white pine seeds during the initial stages of dormancy maintenance; at this time, ABA levels decreased by approximately two-thirds in both embryo and megagametophyte tissues. Gibberellic acid treatments, both alone and in combination with fluridone, suggested that GA acted transiently to disrupt ABA homeostasis by shifting the ratio between biosynthesis and catabolism to favor ABA catabolism or transport. Increases in phaseic acid (PA) and dihydrophaseic acid (DPA) were observed during fluridone/GA treatments; however, increases in ABA metabolites did not account for the reduction in ABA observed; additional catabolism and/or transport of ABA and selected metabolites in all probability accounts for this discrepancy. Finally, levels of 7′ hydroxy-ABA (7′OH-ABA) were higher in dormant-imbibed seeds, suggesting that metabolism through this pathway is increased in seeds that maintain higher levels of ABA, perhaps as a means to further regulate ABA homeostasis.

Comparative effects of some plant growth regulators on the germination of barley and radish seeds under high temperature stress

Abstract: The effects of gibberellic acid, kinetin, benzyladenine, ethylene, 24-epibrassinolide, triacontanol and polyamines (cadaverine, putrescine, spermidine, spermine), alone or in combinations, on germination and early seedling growth under high temperature conditions of barley and radish seeds were studied. High temperature both delayed and inhibited the germinations of both the species. Only three of the single applications gibberellic acid, kinetin and 24-epibrassinolide could alleviate the effects of high temperature on germination of barley seeds. All the combinations composed of these three growth regulators removed more successfully this adverse effect on germination. High temperature effect on the germination of radish seeds was overcome by all the pretreatments alone or in combinations to varying degrees. Although the mentioned regulators carried on their success on the early growth of barley seedlings, the regulators used for radish had no effect on the seedlings in general.

Multiple environmental signals required for embryo growth and germination of seeds of Selinum carvifolia (L.) L. and Angelica sylvestris L. ( Apiaceae )

Abstract: Germination and dormancy breaking requirements were studied in Selinum carvifolia (L.) L. and Angelica sylvestris L. (Apiaceae). Seeds of these two species have an underdeveloped embryo and are morpho-physiologically dormant. The embryo does not start to grow until physiological dormancy is broken by cold stratification. Incubating seeds at fluctuating temperatures in the light, after cold stratification, had a stimulating effect on embryo growth and seed germination. Seeds of S. carvifolia and A. sylvestris have non-deep simple morphophysiological dormancy (MPD), since gibberellic acid (GA3) could substitute for cold stratification. This is the first report of non-deep simple MPD that is broken by cold stratification in the Apiaceae. Under natural conditions, physiological dormancy is broken by low temperature conditions during winter. Embryo growth and germination occur in a short time interval when temperatures start rising in early spring. Due to the fact that multiple environmental signals regulate dormancy, seedling emergence in these species is timed very accurately in spring.

Gibberellic acid and triacontanol can ameliorate the opium yield and morphine production in opium poppy (Papaver somniferum L.)

Abstract: A pot experiment was conducted during 2004–2005 on opium poppy (Papaver somniferum L.) and the influence of 10−6 M gibberellic acid (GA3) and 10−6 M triacontanol (TRIA) either alone or together, on...

Effects of plant hormones and 20-hydroxyecdysone on tomato (Lycopersicum esculentum) seed germination and seedlings growth

Abstract: 20-hydroxyecdysone (20E) is the major phytoecdysteroid of about 6% of plants. Its role in plant physiology has not been fully elucidated. In this work we studied the effects of 20E application on some morphological and biochemical parameters of tomato, Lycopersicum esculentum, seed during germination and seedling development (5 d). We compared the 20E effects with the action of phytohormones: gibberellic acid (GA3), naftalen acetic acid (NAA), benzyl amino purine (BAP). NAA treatment resulted in marked reduction in shoot length. GA3 treatment promoted maximal shoot elongation. BAP affected negatively shoot length only at late stages, while 20E application stimulated shoot elongation at early stages and reduced it on the fifth day; NAA inhibited root elongation all along the test period. GA3 treatment had no effect on root length, whereas BAP showed strong inhibition on root elongation. On the other hand, 20E showed a weak inhibition of root elongation on the fifth day. As compared to control and to other treatments, NAA and 20E provoked a drastic decrease in protein contents during seedling growth, whereas a high increase was observed under BAP treatment. Electrophoresis revealed that protein bands were not degraded and mobilized after NAA treatment while in control or after 20E and others phytohormones applications, protein patters displayed weak band intensities and some of them were not detected. NAA, GA3 and BAP provoked a decrease in proline content during seedlings, while the effect of 20E on proline levels varied during germination and plantlet development. This work showed that 20E like phytohormones fulfil some bioactive actions during germination and seedlings growth in tomato.

Effect of plant growth regulators on growth and biosynthesis of phenolic compounds in genetically transformed hairy roots ofPanax ginseng C. A. Meyer

Abstract: In this study, morphological alterations, biomass growth, and secondary metabolite production of genetically transformed hairy roots ofPanax ginseng C. A. Meyer, were evaluated after administration of plant growth regulators. The addition of benzylamino purine and kinetin to the culture media increased biomass formation and phenolic compound biosynthesis in the hairy roots. α-Naphthaleneacetic acid and indole-3-butyric acid inhibited hairy root growth, however, low concentrations of indole-3-acetic acid slightly increased hairy root growth. Low concentrations of 2,4-Dichlorophenoxyacetic acid profoundly inhibited growth of hairy roots. The addition of plant growth regulators, such as auxin, did not increase total phenolic compounds in hairy roots that did not contain gibberellic acid and cytokinins. Callus formation was induced in cultures suspended in liquid medium amended with benzylamino purine and kinetin. Hairy roots regenerated from these calluses exhibited an active growth pattern with extensive lateral branching in non-amended medium, similar to the growth pattern of the original hairy roots.

Efficient Agrobacterium-mediated transformation of Vigna mungo using immature cotyledonary-node explants and phosphinothricin as the selection agent

Abstract: Herbicide (Basta®)-tolerant Vigna mungo L. Hepper plants were produced using cotyledonary-node and shoot-tip explants from seedlings germinated in vitro from immature seeds. In vitro selection was performed with phosphinothricin as the selection agent. Explants were inoculated with Agrobacterium tumefaciens strain LBA4404 (harboring the binary vector pME 524 carrying the nptII, bar, and uidA genes) in the presence of acetosyringone. Shoot regeneration occurred for 6 wk on regeneration medium (MS medium with 4.44 μM benzyl adenine, 0.91 μM thidiazuron, and 81.43 μM adenine sulfate) with 2.4 mg/l PPT, explants being transferred to fresh medium every 14 d. After a period on elongation medium (MS medium with 2.89 μM gibberellic acid and 2.4 mg/l PPT), β-glucuronidase-expressing putative transformants were rooted in MS medium with 7.36 μM indolyl butyric acid and 2.4 mg/l PPT. β-Glucuronidase expression was observed in the primary transformants (T0) and in the seedlings of the T1 generation. Screening 128 GUS-expressing, cotyledonary-node-derived, acclimatized plants by spraying the herbicide Basta® at 0.1 mg/l eliminated nonherbicide-resistant plants. Southern hybridization analysis confirmed the transgenic nature of the herbicide-resistant plants. All the transformed plants were fertile, and the transgene was inherited by Mendelian genetics. Immature cotyledonary-node explants produced a higher frequency of transformed plants (7.6%) than shoot-tip explants (2.6%).

Direct shoot bud induction and plant regeneration in Capsicum frutescens Mill.: influence of polyamines and polarity

Abstract: Direct shoot bud induction and plant regeneration was achieved in Capsicum frutescens var. KTOC. Aseptically grown seedling explants devoid of roots, apical meristem and cotyledons were inoculated in an inverted position in medium comprising of Murashige and Skoog (Physiol Plant 15:472–497, 1962) basal medium supplemented with 2-(N-morpholine) ethanesulphonic acid buffer along with 2.28 lM indole- 3-acetic acid, 10 lM silver nitrate and either of 13.31– 89.77 lM benzyl adenine (BA), 9.29–23.23 lM kinetin, 0.91–9.12 lM zeatin, 2.46–9.84 lM 2-isopentenyl adenine. Profuse shoot bud induction was observed only in explants grown on a media supplemented with BA (26.63 lM) as a cytokinin source and 19.4 ± 4.2 shoot buds per explant was obtained in inverted mode under continuous light. Incorporation of polyamine inhibitors in the culture medium completely inhibited shoothoot bud induction. Incorporation of exogenous polyamines improved the induction of shoot buds under 24 h photoperiod. These buds were elongated in MS medium containing 2.8 lM gibberellic acid. Transfer of these shoots to hormone-free MS medium resulted in rooting and rooted plants were transferred to fields. This protocol can be efficiently used for mass propagation and presumably also for regeneration of genetically transformed C. frutescens.

Morpho-histological study on shoot bud regeneration in cotyledon cultures of pepper (Capsicum annuum)

Abstract: Adventitious organogenetic structures were produced in vitro using cotyledon explants excised from 14 day-old pepper seedlings. The best response was observed on MS medium containing 5.7 μM indole-3-acetic acid and 8.8 μM 6-benzylaminopurine. However, when transferred onto elongation medium (MS + 2.8 μM gibberellic acid), these structures frequently developed into leaf-like features rather than into normal shoots. Interestingly, the histological study conducted on the cut end of the cotyledonary petiole revealed a direct induction of numerous teratological protuberances that arise around the cut end of the explant. On the contrary, typical organized bud meristems were rarely observed. Thus, the low number of plants obtained after transfer onto elongation medium seems to be a consequence of this teratological developmental process, frequently associated with fasciated and degenerative meristems, rather than a defect in shoot development from available meristems.