Enhanced transformation of tomato co-cultivated with Agrobacterium tumefaciens C58C1Rifr::pGSFR1161 in the presence of acetosyringone

Summary Explants of tomato (Lycopersicon esculentum Mill cv. Ailsa Craig) were co-cultivated with Agrobacterium tumefaciens C58C1Rif^r::pGSFR1161 in the presence of 20 (M acetosyringone). Transformed root clones were selected on kanamycin medium and the presence of the nptII gene in the plant DNA confirmed by the polymerase chain reaction. Root clones derived from acetosyringone treatment grew more vigorously in the presence of kanamycin and synthesized a greater amount of NPT-II enzyme. The conclusion is that acetosyringone treatment enhances the transformation process, possibly by stimulating multiple insertions of the T-DNA into the host genome.Abbreviations AS acetosyringone - CTAB hexadecyltrimethylammonium bromide - EDTA ethylenediaminetetraacetic acid - ELISA enzyme-linked immunosorbant assay - MS Murashige and Skoog (1962) medium - PCR polymerase chain reaction     

The biosynthesis of acetovanillone in tobacco cell-suspension cultures

A soluble enzyme, extracted from tobacco cell-suspension cultures 24 h after treatment with 100 μM methyl jasmonate, has been shown to synthesize acetovanillone (apocynin) from feruloyl-CoA in the presence of NAD. The enzyme displayed Michaelis-Menten kinetics with apparent K_m values of 5.6 μM for feruloyl-CoA and 260 μM for NAD and exhibited very high specificity for its substrates. The increase in acetovanillone synthase activity was followed by an increase in the concentration of both acetovanillone and acetosyringone in the culture medium. No intermediate could be detected when analysing the reaction medium by HPLC during the formation of acetovanillone in cell-free extracts. The apparent molecular mass estimated by gel permeation on an FPLC column was ca. 79 kDa. To our knowledge, this is the first report of an enzymic system catalysing the synthesis of an acetophenone. This work demonstrates that the biosynthesis of acetophenones in tobacco proceeds from hydroxycinnamic acids through a CoA-dependent β-oxidation pathway. Interestingly in methyl jasmonate-treated cells, which synthesize very large amounts of hydroxycinnamoylputrescines, inhibition of the synthesis of these conjugates increased the concentration of acetovanillone and acetosyringone in the culture medium, suggesting that the two metabolic pathways can compete for their common precursors, i.e. hydroxycinnamoyl-CoA thioesters.     

Genetic transformation of <Emphasis Type="Italic">Agave salmiana</Emphasis> by <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis> and particle bombardment

Agave salmiana was transformed using two different protocols: co-cultivation with Agrobacterium tumefaciens and particle bombardment. The uidA (β-glucuronidase) gene was used as a reporter gene for both methods whereas the nptII and bar genes were used as selectable markers for A. tumefaciens and biolistic transformation respectively. Previous reports for in vitro regeneration of A. salmiana have not been published; therefore the conditions for both shoot regeneration and rooting were optimized using leaves and embryogenic calli of Agave salmiana. The transgenes were detected by Polymerase Chain Reaction (PCR) in 11 month old plants. The transgenic nature of the plants was also confirmed using GUS histochemical assays. Transformation via co-cultivation of explants with Agrobacterium harbouring the pBI121 binary vector was the most effective method of transformation, producing 32 transgenic plants and giving a transformation efficiency of 2.7%. On the other hand, the biolistic method produced transgenic calli that tested positive with the GUS assay after 14 months on selective medium while still undergoing regeneration.     

Efficient <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation of <Emphasis Type="Italic">Vigna mungo</Emphasis> using immature cotyledonary-node explants and phosphinothricin as the selection agent

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%).     

Transgenic Acacia sinuata from Agrobacterium tumefaciens-mediated transformation of hypocotyls

Transgenic herbicide tolerant Acacia sinuata plants were produced by transformation with the bar gene conferring phosphinothricin resistance. Precultured hypocotyl explants were infected with Agrobacterium tumefaciens strain EHA105 in the presence of 100 μM acetosyringone and shoots regenerated on MS (Murashige and Skoog, 1962, Physiol Plant 15:473–497) medium with 13.3 μM benzylaminopurine, 2.6 μM indole-3-acetic acid, 1 g l⁻¹ activated charcoal, 1.5 mg l⁻¹ phosphinothricin, and 300 mg l⁻¹ cefotaxime. Phosphinothricin at 1.5 mg l⁻¹ was used for the selection. Shoots surviving selection on medium with phosphinothricin expressed GUS. Following Southern hybridization, eight independent shoots regenerated of 500 cocultivated explants were demonstrated to be transgenic, which represented transformation frequency of 1.6%. The transgenics carried one to four copies of the transgene. Transgenic shoots were propagated as microcuttings in MS medium with 6.6 μM 6-benzylaminopurine and 1.5 mg l⁻¹ phosphinothricin. Shoots elongated and rooted in MS medium with gibberellic acid and indole-3-butyric acid, respectively both supplemented with 1.5 mg l⁻¹ phosphinothricin. Micropropagation of transgenic plants by microcuttings proved to be a simple means to bulk up the material. Several transgenic plants were found to be resistant to leaf painting with the herbicide Basta.     

The effect of cocultivation treatments on transformation efficiency in pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

The effect of chemical additives (acetosyringone, AS; L-cysteine, CYS; dithiothreitol, DTT; glutathione, GSH; cellulase, CEL; pectinase, PEC) and light regimes (16/8 light/dark photoperiod, 16L/8D; continuous light, 24L; continuous dark, 24D) applied during cocultivation procedure of pea explants with Agrobacterium tumefaciens on transformation efficiency was studied. A hypervirulent strain of A. tumefaciens EHA 105 with two plasmids, namely pGT89 and pBIN19, both carrying reporter gus-int gene, and bar or nptII selectable marker gene, respectively, was used for genetic transformation of cotyledonary node explants of three dry seed pea cultivars Adept, Komet and Menhir. The focus was laid on cocultivation step (48 h) of transformation protocol. After chemical or physical treatments, transient GUS expression was recorded 20 days after cocultivation as a measure of successful transformation, using a four category scale (0 – without GUS expression, 1 – weak, 2 – medium and 3 – strong GUS expression) for calculation of IGE (Intensity of GUS Expression). Of the tested chemical cocultivation additives, 100 μM AS and 50 mg CYS significantly improved GUS expression (IGE value), while DTT, GSH and both macerating enzymes (CEL, PEC used either separately or in combination) either had no positive effect or were even negative. There were no statistically significant differences between the light regimes tested. Nevertheless, cocultivation in 24L, without chemical additives, reproducibly resulted in the highest frequency of explants scored in category 3 of GUS expression (followed by 24D and 16L/8D treatment). However, application of 100 μM AS reverted this trend. Cv. Adept yielded higher transformation frequencies than cvs. Menhir and Komet. Plasmid pGT89 produced a higher IGE value than pBIN19. Based on our results, the improved cocultivation step for pea consists of 48 h cocultivation at 20 ± 2°C, with 50 mg l⁻¹ CYS and 100 μM AS, 16L/8D photoperiod (or without AS in continuous light).     

Agrobacterium-mediated transformation of leaf base derived callus tissues of popular indica rice (Oryza sativa L. sub sp. indica cv. ADT 43)

A simple and efficient protocol for the Agrobacterium-mediated transformation of an agronomically useful abiotic sensitive popular indica rice cv. ADT 43 has been developed. Initiation of calli were best achieved from the leaf bases of 4 days old rice seedlings on LS medium supplemented with 2.5 mg/L 2,4-D and 1.0 mg/L thiamine-HCl. Rice calli immersed in Agrobacterium suspension (strain EHA 105, OD₆₀₀ = 0.8) were co-cultured on LS30-AsPC medium for 2 days at 25 ± 2 °C in the dark. Based on GUS expression analysis, 10 min co-cultivation time with 100 μM acetosyringone was found optimum for the delivery of gus gene. Calli were proved to be very sensitive to Agrobacterium infection and we found that the level of necrotic response can be minimized after co-cultivation with 30% LS, 10 g/L PVP, 10% coconut water and 250 mg/L timentin which improved the final transformation efficiency to 9.33%. Molecular and genetic analysis of transgenic plants reveals the integration, expression and inheritance of transgene in the progeny (T₁) of these plants. The copy number of transgenes has been found to vary from 1 to 2 in transgenic plants (T₀ and T₁).     

Initiation of and solasodine production in hairy root cultures of Solanum mauritianum Scop.

Initiation and establishment of hairy root cultures from leaf or seedling hypocotyl explants of Solanum mauritianum Scop., using six strains of Agrobacterium rhizogenes was attempted. Success was only achieved following hypocotyl inoculation with strain LBA 9402. Transformation frequency was very low, with only one instance out of a possible 90 being recorded. Resultant hairy root cultures grew rapidly and could be maintained using a Murashige and Skoog (1962) medium supplemented with 0.1 g L^–1 myo-inositol and 3% sucrose, either as a solid or liquid culture. Under these conditions, the roots had a solasodine content of 126 g g^–1 DW. Lower levels of solasodine and decreased root growth rates were recorded when the medium strength was reduced by half or 3% glucose substituted for the 3% sucrose.Abbreviations MS Murashige and Skoog's (1962) medium     

A spectroscopic characterization of a phenolic natural mediator in the laccase biocatalytic reaction

Multi-frequency ESR combined with NALDI-TOF MS has been used for the characterization of 3,5-dimethoxy-4-hydroxyacetophenone radical intermediate and by-products formed during the Coriolopsis gallica laccase catalytic reaction. A stable radical species is formed and an intense and well-structured ESR spectrum was detected and fully characterized at S-, X- and W-bands. The presence of by-products generated as the result of by-reactions has been investigated and analyzed through NALDI-TOF MS, performing the experiments versus time. The superior radical stability of such phenoxy radical, due to steric hindrance in ortho to the phenol group and the great delocalization of the unpaired electron on the acetyl substituent, makes acetosyringone particularly interesting for biotechnological applications. This represents a good example for the development of new stable laccase mediator molecules.     

Factors that influence Agrobacterium rhizogenes-mediated transformation of broccoli (Brassica oleracea L. var. italica)

 An improved broccoli transformation system was developed by optimising several factors that affect the rate of effective Agrobacterium-mediated transformation. Leaf explants of cultivar Shogun were co-cultivated with Agrobacterium rhizogenes strain A4T harbouring the binary vector pART278. The T-DNA of this binary vector contains a neomycin phosphotransferase II (NOS-NPTII-NOS) gene for kanamycin resistance and a β-glucuronidase (35S-GUS-OCS) gene. Several media and factors were evaluated including combinations of arginine, mannopine, acetosyringone and the use of feeder cell layers. The new protocol includes the use of 200 μm acetosyringone in LB medium for bacterial growth, the use of a Brassica campestris feeder cell layer, 10 mm mannopine and 50 μm acetosyringone in the co-cultivation medium and 1 mm arginine in the selection medium. The use of this optimised protocol produced transformation rates of 33% in preliminary experiments transforming broccoli with the antisense 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene from pTOM13. Received: 2 July 1998 / Revision received: 9 February 2000 / Accepted: 17 February 2000