<Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated genetic transformation of <Emphasis Type="Italic">Perilla frutescens</Emphasis>

A reproducible plant regeneration and an Agrobacterium tumefaciens-mediated genetic transformation protocol were developed for Perilla frutescens (perilla). The largest number of adventitious shoots were induced directly without an intervening callus phase from hypocotyl explants on MS medium supplemented with 3.0 mg/l 6-benzylaminopurine (BA). The effects of preculture and extent of cocultivation were examined by assaying -glucuronidase (GUS) activity in explants infected with A. tumefaciens strain EHA105 harboring the plasmid pIG121-Hm. The highest number of GUS-positive explants were obtained from hypocotyl explants cocultured for 3 days with Agrobacterium without precultivation. Transgenic perilla plants were regenerated and selected on MS basal medium supplemented with 3.0 mg/l BA, 125 mg/l kanamycin, and 500 mg/l carbenicillin. The transformants were confirmed by PCR of the neomycin phosphotransferase II gene and genomic Southern hybridization analysis of the hygromycin phosphotransferase gene. The frequency of transformation from hypocotyls was about 1.4%, and the transformants showed normal growth and sexual compatibility by producing progenies.     

Regeneration from leaf-base explants of <Emphasis Type="Italic">Lolium perenne</Emphasis> L. and <Emphasis Type="Italic">Lolium multiflorum</Emphasis> L.

The regenerability of Lolium perenne and Lolium multiflorum was investigated using leaf-base sections excised from plantlets grown in vitro. Young leaf bases were cut into three sections each 2 mm in length, the lowest 0–2 mm section adjacent to, but not including, the apical meristem. Callus development followed by embryogenesis occurred only in the lowest 2 mm leaf-base sections of L. perenne cv. Limes, whereas L. multiflorum leaf bases showed an embryogenic response along the entire 6 mm section. Rooted, green plantlets were obtained from 100% of the 0–2 mm sections of L. perenne cv. Limes and from 91%, 65% and 26% of leaf-base sections at 0–2, 2–4 and 4–6 mm respectively from L. multiflorum. Microprojectile bombardment of leaf-base explants resulted in transient expression of the -glucuronidase gene.     

Regeneration and<Emphasis Type="Italic"> Agrobacterium-</Emphasis>mediated transformation of hop (<Emphasis Type="Italic">Humulus lupulus</Emphasis> L.)

An efficient procedure for direct organogenesis and regeneration of hop (Humulus lupulus L.) was established. For the first time Agrobacterium-mediated genetic transformation of hop (cv. "Tettnanger") was achieved. Shoot internodes from in vitro cultures were identified as the most suitable type of explant for regeneration. Using this type of explant, a shoot-inducing medium was developed that supported direct organogenesis of approximately 50% of the explants. Plantlets were successfully rooted and transferred to the greenhouse. Overall, in less than 6 months hop cultures propagated in vitro were regenerated to plants in the greenhouse. Agrobacterium-mediated genetic transformation was performed with the reporter gene GUS (-glucuronidase). The presence and function of transgenes in plants growing in the greenhouse was verified by PCR (polymerase chain reaction) and enzyme assay for GUS activity, respectively. We have obtained 21 transgenic plants from 1,440 explants initially transformed, yielding an overall transformation efficiency of 1.5%.Abbreviations BAP 6-Benzylaminopurine - GA₃ Gibberellic acid - GUS -Glucuronidase - IAA Indole-3-acetic acid - IBA Indole-3-butyric acid - NAA -Naphthaleneacetic acid - nptII Neomycin phosphotransferase II - PCR Polymerase chain reaction - TDZ 1-Phenyl-3-(1,2,3-thiadiazol-5-yl) urea (thidiazuron)Communicated by H. Lörz     

<Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>-mediated transformation of blueberry (<Emphasis Type="Italic">Vaccinium corymbosum</Emphasis> L.)

Transient expression studies using blueberry leaf explants and monitored by -glucuronidase (GUS) assays indicated Agrobacterium tumefaciens strain EHA105 was more effective than LBA4404 or GV3101; and the use of acetosyringone (AS) at 100 M for inoculation and 6 days co-cultivation was optimum compared to 2, 4, 8, 10 or 12 days. Subsequently, explants of the cultivars Aurora, Bluecrop, Brigitta, and Legacy were inoculated with strain EHA105 containing the binary vector pBISN1 with the neomycin phosphotransferase gene (nptII) and an intron-interrupted GUS gene directed by the chimeric super promoter (Aocs)₃AmasPmas. Co-cultivation was for 6 days on modified woody plant medium (WPM) plus 100 M AS. Explants were then placed on modified WPM supplemented with 1.0 mg l^–1 thidiazuron, 0.5 mg l^–1 -naphthaleneacetic, 10 mg l^–1 kanamycin (Km), and 250 mg l^–1 cefotaxime. Selection for Km-resistant shoots was carried out in the dark for 2 weeks followed by culture in the light at 30 E m^–2 s^–1 at 25°C. After 12 weeks, selected shoots that were both Km resistant and GUS positive were obtained from 15.3% of the inoculated leaf explants of cultivar Aurora. Sixty-eight independent clones derived from such shoots all tested positive by the polymerase chain reaction using a nptII primer. Eight of eight among these 68 clones tested positive by Southern hybridization using a gusA gene derived probe. The transformation protocol also yielded Km-resistant, GUS-positive shoots that were also PCR positive at frequencies of 5.0% for Bluecrop, 10.0% for Brigitta and 5.6% for Legacy.     

Genetic transformation and regeneration of transgenic plants from precultured cotyledon and hypocotyl explants of <Emphasis Type="Italic">Eucalyptus tereticornis</Emphasis> Sm. using <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>

An efficient transformation protocol was developed for Eucalyptus tereticornis Sm. using cotyledon and hypocotyl explants. Precultured cotyledon and hypocotyl explants were cocultured with Agrobacterium tumefaciens strain LBA 4404 harboring the binary vector pBI121 containing the uidA and neomycin phosphotransferase II genes for 2 d and transferred to selective regeneration medium containing 0.5 mg/l 6-benzylaminopurine (BAP), 0.1 mg/l naphthalene acetic acid, 40 mg/l kanamycin, and 300 mg/l cefotaxime. After two passages in the selective regeneration medium, the putatively transformed regenerants were transferred to Murashige and Skoog (MS) liquid medium containing 0.5 mg/l BAP and 40 mg/l kanamycin on paper bridges for further development and elongation. The elongated kanamycin-resistant shoots were subsequently rooted on the MS medium supplemented with 1.0 mg/l indole-3-butyric acid and 40 mg/l kanamycin. A strong β-glucuronidase activity was detected in the transformed plants by histochemical assay. Integration of T-DNA into the nuclear genome of transgenic plants was confirmed by polymerase chain reaction and southern hybridization. This protocol allows effective transformation and direct regeneration of E. tereticornis Sm.     

<Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>-mediated transformation of chickpea (<Emphasis Type="Italic">Cicer arietinum</Emphasis> L.): gene integration,expression and inheritance

A reproducible method of Agrobacterium-mediated transformation was developed for Cicer arietinum (chickpea). Initial explants consisted of longitudinal slices from embryonic axes of imbibed, mature seed. The plasmid contained a bi-functional fusion gene conferring both -glucuronidase and neomycin phosphotransferase activities, under the control of a 35S35SAMV promoter. Using a series of tissue culture media for co-cultivation, shoot initiation and rooting, we recovered transgenic plants from approximately 1.3% of the sliced embryo axes. The addition of a shoot elongation medium to the protocol improved the success rate to 3.1% but increased the time in tissue culture. Inheritance of the gus gene was followed through four generations, both through expression and Southern hybridization assays, and showed the expected Mendelian inheritance pattern.NRCC Grant No. 46589.     

High frequency <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation and plant regeneration via direct shoot formation from leaf explants in <Emphasis Type="Italic">Beta vulgaris</Emphasis> and <Emphasis Type="Italic">Beta maritima</Emphasis>

We have developed a new procedure for Agrobacterium-mediated transformation of plants in the genus Beta using shoot-base as the material for Agrobacterium infection. The frequency of regeneration from shoot bases was analyzed in seven accessions of sugarbeet (Beta vulgaris) and two accessions of B. maritima to select materials suitable for obtaining transformed plants. The frequency of transformation of the chosen accessions using Agrobacterium strain LBA4404 and selection on 150-mg/l kanamycin was found to be higher than that in previously published methods. Genomic DNA analysis and -glucuronidase reporter assays showed that the transgene was inherited and expressed in subsequent generations. In our method, shoot bases are prepared by a simple procedure, and transformation does not involve the callus phase, thus minimizing the occurrence of somaclonal variations.     

<Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated genetic transformation and development of herbicide-resistant sugarcane (<Emphasis Type="Italic">Saccharum</Emphasis> species hybrids) using axillary buds

Direct regeneration from explants without an intervening callus phase has several advantages, including production of true type progenies. Axillary bud explants from 6-month-old sugarcane cultivars Co92061 and Co671 were co-cultivated with Agrobacterium strains LBA4404 and EHA105 that harboured a binary vector pGA492 carrying neomycin phosphotransferase II, phosphinothricin acetyltransferase (bar) and an intron containing -glucuronidase (gus-intron) genes in the T-DNA region. A comparison of kanamycin, geneticin and phosphinothricin (PPT) selection showed that PPT (5.0 mg l^–1) was the most effective selection agent for axillary bud transformation. Repeated proliferation of shoots in the selection medium eliminated chimeric transformants. Transgenic plants were generated in three different steps: (1) production of putative primary transgenic shoots in Murashige-Skoog (MS) liquid medium with 3.0 mg l^–1 6-benzyladenine (BA) and 5.0 mg l^–1 PPT, (2) production of secondary transgenic shoots from the primary transgenic shoots by growing them in MS liquid medium with 2.0 mg l^–1 BA, 1.0 mg l^–1 kinetin (Kin), 0.5 mg l^–1 -napthaleneacetic acid (NAA) and 5.0 mg l^–1 PPT for 3 weeks, followed by five more cycles of shoot proliferation and selection under same conditions, and (3) rooting of transgenic shoots on half-strength MS liquid medium with 0.5 mg l^–1 NAA and 5.0 mg l^–1 PPT. About 90% of the regenerated shoots rooted and 80% of them survived during acclimatisation in greenhouse. Transformation was confirmed by a histochemical -glucuronidase (GUS) assay and PCR amplification of the bar gene. Southern blot analysis indicated integration of the bar gene in two genomic locations in the majority of transformants. Transformation efficiency was influenced by the co-cultivation period, addition of the phenolic compound acetosyringone and the Agrobacterium strain. A 3-day co-cultivation with 50 M acetosyringone considerably increased the transformation efficiency. Agrobacterium strain EHA105 was more effective, producing twice the number of transgenic shoots than strain LBA4404 in both Co92061 and Co671 cultivars. Depending on the variety, 50–60% of the transgenic plants sprayed with BASTA (60 g l^–1 glufosinate) grew without any herbicide damage under greenhouse conditions. These results show that, with this protocol, generation and multiplication of transgenic shoots can be achieved in about 5 months with transformation efficiencies as high as 50%.Abbreviations BA 6-Benzyladenine - CaMV Cauliflower mosaic virus - GUS -Glucuronidase - Kin Kinetin - NAA -Naphthaleneacetic acid - Nos Nopaline synthase - nptII Neomycin phosphotransferase II - PCR Polymerase chain reaction - PPT Phosphinothricin - YEP Yeast extract and peptone     

Highly efficient <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>-mediated transformation of celery (<Emphasis Type="Italic">Apium graveolens</Emphasis> L.) through somatic embryogenesis

A protocol was developed for rapid and efficient production of transgenic celery plants via somatic embryo regeneration from Agrobacterium tumefaciens- inoculated leaf sections, cotyledons and hypocotyls. These explants were excised from in vitro seedlings of the cvs. XP166 and XP85 and inoculated with A. tumefaciens strain EHA105 containing the binary vector pBISN1. PBISN1 has the neomycin phosphotransferase gene (nptII) and an intron interrupted β-glucuronidase (GUS) reporter gene (gusA). Co-cultivation was carried out for 4 d in the dark on callus induction medium (CIM): Gamborg B5 + 2.79 μM kinetin + 2.26 μM 2,4-dichlorophenoxyacetic acid (2,4-D) supplemented with 100 μM acetosyringone. Embryogenic calluses resistant to kanamycin (Km) were then recovered on CIM + 25 mg l⁻¹ Km + 250 mg l⁻¹ timentin after 12 weeks. Subsequently, a large number of Km-resistant and GUS-positive transformants, tens to hundreds per explant were regenerated via somatic embryogenesis on Gamborg B5 + 4.92 μM 6 (γ,γ-dimethylallylamino)-purine (2iP) + 1.93 μM α-naphthaleneacetic acid (NAA) + 25 mg l⁻¹ Km + 250 mg l⁻¹ timentin after 8 weeks. Using this protocol, the transformation frequency was 5.0% and 5.0% for leaf sections, 17.8% and 18.3% for cotyledons, and 15.9% and 16.7% for hypocotyl explants of cvs. XP85 and XP166, respectively. Stable integration of the model transgenes with 1–3 copy numbers was confirmed in all ten randomly selected transgenic events by Southern blot analysis of gusA. Progeny analysis by histochemical GUS assay showed stable Mendelian inheritance of the transgenes. Thus, A. tumefaciens-mediated transformation of cotyledons or hypocotyls provides an effective and reproducible protocol for large-scale production of transgenic celery plants.     

Production of transgenic lily plants by<Emphasis Type="Italic"> Agrobacterium</Emphasis>-mediated transformation

A system for the production of transgenic plants was developed for the Oriental hybrid lily, Lilium cv. Acapulco, by Agrobacterium-mediated genetic transformation. Filament-derived calli were co-cultivated with A. tumefaciens strain EHA101/pIG121Hm, which harbored a binary vector carrying the neomycin phosphotransferase II, hygromycin phosphotransferase, and intron-containing -glucuronidase genes in the T-DNA region. Six hygromycin-resistant (Hyg^r) culture lines were obtained from 200 calli by scratching them with sandpaper prior to inoculation and using NH₄NO₃-free medium for co-cultivation and a hygromycin-containing regeneration medium for selection. Hyg^r culture lines regenerated shoots, which developed into plantlets following transfer to a plant growth regulator-free medium. All of these plantlets were verified to be transgenic by GUS histochemical assay and inverse PCR analysis.Abbreviations AS Acetosyringone (3,5-dimethoxy-4-hydroxy-acetophenone) - BA Benzyladenine - CaMV Cauliflower mosaic virus - GUS -Glucuronidase - HPT Hygromycin phosphotransferase - Hyg^r Hygromycin-resistant - NOS Nopaline synthase - NPTII Neomycin phosphotransferase II - PGR Plant growth regulator - PIC Picloram (4-amino-3,5,6-trichloropicolinic acid)Communicated by H. Ebinuma     

<Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation of the genome-sequenced poplar clone,nisqually-1 (<Emphasis Type="Italic">Populus trichocarpa</Emphasis>)

The US Department of Energy recently released a 6.8X draft of the genome sequence for Nisqually-1, a genotype of black cottonwood (Populus trichocarpa). To improve its utility for functional genomics research, having an efficient means for transformation and regeneration is necessary. To examine several parameters known to affect the transformation rate, we cocultivated leaf disc and stem explants with a strain ofAgrobacterium tumefaciens harboring a binary plasmid vector containing genes for both neomycin phosphotransferase (NPTII) and β-glucuronidase (GUS). Shoot regeneration from stem explants was observed in the presence of kanamycin when thidiazuron was incorporated in the selection medium. Transformation efficiency was influenced by the level of thidiazuron to which explants were exposed during the early stages of shoot induction. Histochemical assays revealed expression of theGUS gene in leaf, stem, and root tissues of transgenic plants. Polymerase chain reaction confirmed the presence of both selectable marker and reporter genes in all lines that stained positive for β-glucuronidase activity. By use of our modified protocol, transgenic plants were recovered within 6 mo at an efficiency of 6%, adequate to produce a large number of transgenic events with modest effort.     

Loss of AtPIN1 does not influence the <Emphasis Type="Italic">in vitro</Emphasis> morphogenic potential of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> suspension cultures

Suspension cultures from Arabidopsis thaliana wild type and AtPIN1-deficient lines were initiated and maintained for more than 3 years. A protocol for efficient regeneration from long-term suspension cultures was established. Arabidopsis wild-type and respectively AtPIN1 mutant plants have been regenerated from these cultures and characterized. Additionally, transgenic suspension cultures expressing the uidA ( -glucuronidase) reporter gene under the control of AtPIN1 promoter have been used for morphogenic studies. Our studies suggest that a lack of AtPIN1 function affects shoot differentiation and development, but does not influence in vitro regeneration of plants.     

<Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation of <Emphasis Type="Italic">Fraxinus pennsylvanica</Emphasis> hypocotyls and plant regeneration

A genetic transformation protocol for green ash (Fraxinus pennsylvanica) hypocotyl explants was developed. Green ash hypocotyls were transformed using Agrobacterium tumefaciens strain EHA105 harboring binary vector pq35GR containing the neomycin phosphotransferase (nptII) and β-glucuronidase (GUS) fusion gene, and an enhanced green fluorescent protein gene. Pre-cultured hypocotyl explants were transformed in the presence of 100 μM acetosyringone using 90 s sonication plus 10 min vacuum-infiltration. Kanamycin at 20 mg l⁻¹ was used for selecting transformed cells. Adventitious shoots regenerated on Murashige and Skoog medium supplemented with 13.3 μM 6-benzylaminopurine, 4.5 μM thidiazuron, 50 mg l⁻¹ adenine sulfate, and 10% coconut water. GUS- and polymerase chain reaction (PCR)-positive shoots from the cut ends of hypocotyls were produced via an intermediate callus stage. Presence of the GUS and nptII genes in GUS-positive shoots were confirmed by PCR and copy number of the nptII gene in PCR-positive shoots was determined by Southern blotting. Three transgenic plantlets were acclimatized to the greenhouse. This transformation and regeneration system using hypocotyls provides a foundation for Agrobacterium-mediated transformation of green ash. Studies are underway using a construct containing the Cry8Da protein of Bacillus thuringiensis for genetic transformation of green ash.     

High-efficiency biolistic co-transformation and regeneration of 'Chardonnay' (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.) containing<Emphasis Type="Italic"> npt-II</Emphasis> and antimicrobial peptide genes

A reliable and efficient system for transformation and regeneration of 'Chardonnay' (Vitis vinifera L.) plants via microprojectile bombardment was developed. Improvements over the previous biolistic transformation system included: (1) the use of gold particles for bombardment; (2) step-wise selection at 10 then 15 mg/l kanamycin; and (3) embryo induction at 27°C. Embryogenic cell cultures were either bombarded with pBI426, which contains the reporter gene gus (uidA) coding for -glucuronidase (GUS), or were co-bombarded with pSAN237 carrying the npt-II (neomycin phosphotransferase II) selectable marker gene, and a second plasmid with an antimicrobial peptide gene. A large number of transient (7,883±1,928) and stable (46±32) blue spots per plate at 2 and 95 days after bombardment, respectively, were obtained according to GUS expression analyses. A total of 447 putative transgenic embryos was harvested from 84 bombarded plates. From these embryos, 242 (54%) were regenerated into plants within the first year of the experiment. Southern blot analyses confirmed integration of the transgenes into the grape genome. Co-transformation was tested with four separate antimicrobial constructs. The co-transformation frequency of unlinked genes was 48% as measured by polymerase chain reaction (PCR), and 56% as estimated by dot blot hybridization. Expression of the gus gene, and PCR and Southern blot analyses of npt-II and antimicrobial genes from regenerated plants document stable transformation of 'Chardonnay' and establish the parameters for highly-efficient biolistic transformation in V. vinifera.Abbreviations AMP Antimicrobial peptide - DBH Dot blot hybridization - GM+NOA Glycerol and maltose liquid medium with -naphthoxyacetic acid - gus -Glucuronidase gene - GUS -Glucuronidase - Km Kanamycin - Km^R Kanamycin resistant - mag2 Magainin-2 - MS Murashige and Skoog medium - MS/2 Half-strength Murashige and Skoog medium - nos Nopaline synthase - npt-II Neomycin phosphotransferase II gene - PCR Polymerase chain reaction - PGL Peptidyl-glycine-leucine - Pubq3 Arabidopsis ubiquitin-3 promoter - Pubq10-L Arabidopsis ubiquitin-10L promoter - Pubq11 Arabidopsis ubiquitin-11 promoter - SP Signal peptide - Tnos Nopaline synthase terminator - WPM Woody plant mediumCommunicated by E.D. Earle     

Improvement of cotton fiber quality by transforming the<Emphasis Type="Italic"> acsA</Emphasis> and<Emphasis Type="Italic"> acsB</Emphasis> genes into<Emphasis Type="Italic"> Gossypium hirsutum</Emphasis> L. by means of vacuum infiltration

A novel method for the genetic transformation of cotton pollen by means of vacuum infiltration and Agrobacterium-mediated transformation is reported. The acsA and acsB genes, which are involved in cellulose synthesis in Acetobacter xylinum, were transferred into pollen grains of brown cotton with the aim of improving its fiber quality by incorporating useful prokaryotic features into the colored cotton plants. Transformation was carried out in cotton pollen-germinating medium, and transformation was mediated by vector pCAMBIA1301, which contains a reporter gene -glucuronidase (GUS), a selectable marker gene, hpt, for hygromycin resistance and the genes of interest, acsA and acsB. The integration and expression of acsA, acsB and GUS in the genome of transgenic plants were analyzed with Southern blot hybridization, PCR, histochemical GUS assay and Northern blot hybridization. We found that following pollination on the cotton stigma transformed pollen retained its capability of double-fertilization and that normal cotton seeds were produced in the cotton ovary. Of 1,039 seeds from 312 bolls pollinated with transformed pollen grains, 17 were able to germinate and grow into seedlings for more than 3 weeks in a nutrient medium containing 50 mg/l hygromycin; eight of these were transgenic plants integrated with acsA and acsB, yielding a 0.77% transformation rate. Fiber strength and length from the most positive transformants was 15% greater than those of the control (non-transformed), a significant difference, as was cellulose content between the transformed and control plants. Our study suggests that transformation through vacuum infiltration and Agrobacterium mediated transformation can be an efficient way to introduce foreign genes into the cotton pollen grain and that cotton fiber quality can be improved with the incorporation of the prokaryotic genes acsA and acsB.Communicated by D. Bartels     

Establishment of an efficient <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>-mediated leaf disc transformation of <Emphasis Type="Italic">Thellungiella halophila</Emphasis>

Thellungiella halophila is a salt-tolerant close relative of Arabidopsis, which is adopted as a halophytic model for stress tolerance research. We established an Agrobacterium tumefaciens-mediated transformation procedure for T. halophila. Leaf explants of T. halophila were incubated with A. tumefaciens strain EHA105 containing a binary vector pCAMBIA1301 with the hpt gene as a selectable marker for hygromycin resistance and an intron-containing β-glucuronidase gene as a reporter gene. Following co-cultivation, leaf explants were cultured on selective medium containing 10 mg l⁻¹ hygromycin and 500 mg l⁻¹ cefotaxime. Hygromycin-resistant calluses were induced from the leaf explants after 3 weeks. Shoot regeneration was achieved after transferring the calluses onto fresh medium of the same composition. Finally, the shoots were rooted on half strength MS basal medium supplemented with 10 mg l⁻¹ hygromycin. Incorporation and expression of the transgenes were confirmed by PCR, Southern blot analysis and GUS histochemical assay. Using this protocol, transgenic T. halophila plants can be obtained in approximately 2 months with a high transformation frequency of 26%.     

Effect of over-expression of <Emphasis Type="Italic">Linum usitatissimum</Emphasis> PINORESINOL LARICIRESINOL REDUCTASE (<Emphasis Type="Italic">LuPLR</Emphasis>) gene in transgenic <Emphasis Type="Italic">Phyllanthus amarus</Emphasis>

Shoot tip explants of Phyllanthus amarus were cocultivated with Agrobacterium tumefaciens strain LBA 4404 carrying plasmid pCAMBIA 2301 harbouring genes coding for betaglucuronidase (gus), kanamycin (kan), and neomycin phosphotransferase II (nptII) along with a gene coding for Linum usitatissimum PINORESINOL LARICIRESINOL REDUCTASE (Lu-PLR). Transformed shoot tip explants were maintained in a Murashige and Skoog (MS) medium containing TDZ 1.54 mg l^?1, kan 50 mg l^?1 and cephotaxime 62.5 mg l^?1. The optimum medium for regeneration of multiple shoots was MS supplemented with TDZ 1.54 mg l^?1, kan 50 mg l^?1. Efficient and effective rooting of plantlets was achieved by culturing the in vitro regenerated shoots on liquid ½ MS medium containing 0.7 mg l^?1 indole 3-butyric acid (IBA) and 5 mg l^?1 kan. Rooted plants were acclimatized in the mixtures of vermiculite and soil. The transformation of kan-resistant plantlets regenerated from shoot-tip explants was confirmed by GUS and polymerase chain reaction (PCR) analysis. Southern blot and reverse transcribed PCR (RT-PCR) analysis confirmed successful integration and expression of Lu-PLR gene. Quantitative analysis of phyllanthin performed on transgenic and wild plants using high-performance liquid chromatography (HPLC) revealed that transgenic lines contained higher phyllanthin content (0.3–0.81% w/w) than wild plants (0.09% w/w). The highest yield of phyllanthin was detected in transgenic lines was up to 1.16, 1.22 and 1.23 folds higher than that of wild plant. This report highlights the transgenic approach to enhance the contents of phyllanthin and hypophyllanthin.     

A Motility Revertant of the <Emphasis Type="Italic">ndvB</Emphasis> Mutant of <Emphasis Type="Italic">Bradyrhizobium japonicum</Emphasis>

A motility revertant of a Bradyrhizobium japonicum ndvB mutant was isolated and characterized. The ndvB mutants of B. japonicum have been reported to be osmotically sensitive, as well as defective in motility, periplasmic cyclic -(13), (16)-D-glucan synthesis, and symbiosis with soybean. The motility revertant was restored for osmotic tolerance but not for cyclic -glucan production or effective symbiosis. These results support our hypothesis that cyclic -glucans have an important role in symbiosis—the suppression of a plant defense response—in addition to their role in periplasmic osmoprotection.     

Transfer and expression of <Emphasis Type="Italic">npt</Emphasis>II and <Emphasis Type="Italic">bar</Emphasis> genes in cucumber (<Emphasis Type="Italic">Cucumis satavus</Emphasis> L.)

Summary The generation of transgenic Cucumis sativus cv. Greenlong plants resistant to phosphinothricin (PPT) was obtained using Agrobacterium tumefaciens-mediated gene transfer. The protocol relied on the regeneration of shoots from cotyledon explants. Transformed shoots were obtained on Murashige and Skoog medium supplemented with 4.4 μM 6-benzylaminopurine 3.8 μM abscisic acid, 108.5 μM adenine sulfate, and 2 mg l⁻¹ phosphinothricin. Cotyledons were inoculated with the strain EHA105 harboring the neomycin phosphotransferase II (npt II), and phosphinothricin resistance (bar) genes conferring resistance to kanamycin and PPT. Transformants were selected by using increasing concentrations of PPT (2–6 mg l⁻¹). Elongation and rooting of putative transformants were performed on PPT-containing (2 mg l⁻¹) medium with 1.4 μM gibberellic acid and 4.9 μM indolebutyric acid, respectively. Putative transformants were confirmed for transgene insertion through PCR and Southern analysis. Expression of the bar gene in transformed plants was demonstrated using a leaf painting test with the herbicide Basta. Pre-culture of explants followed by pricking, addition of 50 μM acetosyringone during infection, and selection using PPT rather than kanamycin were found to enhance transformation frequency as evidenced by transient β-glucuronidase assay. Out of 431 co-cultivated explants, 7.2% produced shoots that rooted and grew on PPT, and five different plants (1.1%) were demonstrated to be transgenic following Southern hybridization.     

High-frequency transformation of<Emphasis Type="Italic"> Lobelia erinus</Emphasis> L. by<Emphasis Type="Italic"> Agrobacterium</Emphasis>-mediated gene transfer

A highly efficient transformation procedure was developed for Lobelia erinus. Leaf or cotyledon discs were inoculated with Agrobacterium tumefaciens strain EHA105 harboring the binary vector plasmid pIG121Hm, which contains a -glucuronidase gene with an intron as a reporter gene and both the neomycin phosphotransferase II and hygromycin phosphotransferase genes as selectable markers. The hygromycin-resistant calli produced on the selection medium were transferred to MS medium supplemented with 0.5 mg/l benzyladenine and 0.2 mg/l indole-3-acetic acid for regeneration of adventitious shoots. Transgenic plants were obtained as a result of the high regeneration rate of the transformed calli, which was as high as 83%. In contrast, no transgenic plant was obtained by the procedure of direct shoot formation following inoculation with A. tumefaciens. Transgenic plants flowered 3–4 months after transformation. Integration of the transgenes was detected using PCR and Southern blot analysis, which revealed that one to several copies were integrated into the genomes of the host plants. The transformation frequency at the stage of whole plants was very high—45% per inoculated disc.Abbreviations BA: 6-Benzyladenine - 2,4-D: 2,4-Dichlorophenoxyacetic acid - GUS: -Glucuronidase - IAA: Indole-3-acetic acidCommunicated by G.C. Phillips