AGROBACTERIUM-MEDIATED TRANSFORMATION OF TWO TOMATO CULTIVARS (LYCOPERSICON ESCULENTUM MILL.) CV. SANDRA AND ROCKY

An efficient protocol for Agrobacterium-mediated transformation of tomato cultivars Sandra and Rocky was conducted to examine the possibility of producing transgenic tomato plants cultivars harbouring the nptII gene, conferring kanamycin resistance. To achieve this aim, tomato cotyledon explants were transformed using EHA105 Agrobacterium tumefaciens strain harboring the binary vectors pBI121 which contains Gus gene, and neomycin phosphotransferase II (nptII) as selectable marker gene under the control of a CaMV35S promoter and nopaline synthase (nos) Terminator. Transformant detection was carried out in three distinct ways. First antibiotic selection, Kanamycin at a concentration of100 mgl-1 found to be efficient for this purpose. Second histochemical GUS assay revealed the presence of blue colored zones in a number of shoots and leaves for both in vitro and the greenhouse-grown transgenic plants. Third PCR analysis indicated positive result by showing the fragment for nptII gene in tested transformants, while was absent in non-transgenic control (wild type). On the other hand, the results showed that Sandra cultivar was more efficient for regeneration and subsequently transformation frequency than Rocky cultivar, which record 26.66% of transformation frequency compared with 11.57% in Rocky cultivar.

Genetic Transformation for Pod Borer Resistance in Dolichos Bean [Lablab purpureus (L.) Sweet]

Background: Agrobacterium mediated genetic transformation experiments were carried out in Dolichos bean Cv. (Konkan Bhushan) showing better regenerability. Methods: Three cry genes viz. cry1Aabc, cry1Fa1 and cry2Aa were used for the transformation each of which were linked to CaMV35S promoter and nptII gene under control of nos promoter and terminator. A vector system consisting of the disarmed hyper virulent Agrobacterium tumefaciens strain EHA-105 harboring pBinAR or BinBt3 was used. Mature embryo axis with single cotyledon was used as explant. Kanamycin as well as PCR screening was carried out to assess the transformation frequency. Progeny analysis using PCR was also carried out to assess the transgene segregation and stable transformation.Result: Kanamycin concentration of 500 mg/l was found as optimum for selection of a transgenic turning leaf blades albino. Among five methods of colonization used, the method employing mild injury to explant with dipping in Agrobacterium culture for 20 minutes followed by co-cultivation for 48 hours, cefotaxime washing and sowing in soil resulted in maximum survival (74.80%) associated with maximum transformation frequency through PCR analysis (2.13%). Among three cry genes, the gene cry2Aa was found the most effective in transforming Dolichos bean. The progeny analysis of transformants has shown the 3:1 mendelian segregation ratio confirming stable transformation of transgene.

Deciphering the role of fungal calmodulin gene using Host-mediated gene silencing approach in apple

Premature leaf fall caused by Marssonina coronaria is one of the most destructive diseases of apple in India. In this study, host induced gene silencing approach was exploited to develop resistance to this disease in an apple cultivar ‘Red Chief’. Calmodulin gene (CaM) having its role in fungal differentiation, development and pathogenicity was selected as target. hpRNAi construct was prepared from the conserved off target free partial gene sequence of CaM and used for transformation trials. Upto 6% kanamycin resistant shoots were obtained on selective medium having 5–6 mg/l kan after 7 weeks of coculture. In PCR analysis of 13 RNAi putative transformants, 10 lines were found positive with CaM and nptII gene specific primers and six lines showed hybridization signal. Semi qRT-PCR revealed variable levels of transgene expression among RNAi lines which seems to be related to copy number of integrated gene. In vitro detached leaf assay revealed lesion development and disease progression in wild type after 5 dpi but not visible in five CaM RNAi lines. Microscopic examination of infected control leaves showed fully developed, septate mycelium, and conidia along with necrosis of whole tissue while three transformants showed reduced growth and differentiation of fungus and in rest three, hyphal development and necrosis were strongly restricted. We conclude that trafficking of dsRNA/ siRNA from apple plants to pathogen might have triggered the down regulation of fungal CaM gene which confirms that deciphering the role of CaM through HIGS lead to resistance to Marssonina blotch in apple.

An Efficient Method for the Genetic Transformation of Acmella oleracea L. (Spilanthes acmella Linn.) with Agrobacterium tumefaciens

Acmella oleracea L. is an important medicinal plant, commonly known as the toothache plant. It is a rich source of secondary metabolites used for the treatment of different human disorders. The demand for Acmella oleracea L. has increased due to its putative health benefits (in terms of both biomass quantity and bioactive compound purification). In vitro plant cultures have allowed the rapid increase of raw material availability through the use of suitable regeneration and multiplication systems. On the other hand, there is a general lack of methods for Acmella genetic transformation as a promising new technological approach for the improvement of secondary metabolites. In this work, an efficient transformation protocol has been established using the Agrobacterium tumefaciens LBA4404 strain bearing the binary vector pBI121 containing the NPTII gene for the resistance to kanamycin. Plant genetic transformation has been verified by direct polymerase chain reaction and GUS assay on regenerants. Transformation efficiency has been affected by the high level of the selection agent kanamycin. To our knowledge, this is the first report on the genetic transformation of A. oleracea, paving the way to further studies to improve in vitro plant growth and secondary metabolite production.

Optimization of genetic transformation method for an indica rice (Oryza sativa L.) variety Ratnagiri-711

A study for method optimization of Agrobacterium-mediated genetic transformation for insect resistance was carried out for a rice variety Ratnagiri-711 showing better regenerability. Three different cry genes viz. cry1Aabc, cry1Fa1 and cry2Aa with a vector system consisting of the disarmed hyper virulent Agrobacterium tumefaciens strain EHA-105 harboring pBinAR or BinBt3 were used. The respective genes were linked to CaMV35S promoter and nptII gene under control of nos promoter and terminator. Scutellum-derived callus bits and embryonic shoot apical meristem of germinating seeds were used as target tissues for callus-mediated and in planta transformation, respectively. Kanamycin screening and PCR analysis was employed for confirmation of presence of transgene. Among five methods of colonization and co-cultivation tried with three cry genes, a callus-mediated transformation method consisting of 20 minutes colonization and 3 days co-cultivation with cry2Aa gene recorded highest transformation frequency (13.79%) but minimum survival (5.27%). On the contrary, considerable transformation frequency (6.35%) with highest survival (79.42%) was observed in an in planta method employing mild injury to embryonic shoot apical meristem of germinating seeds followed by injection of Agrobacterium having cry2Aa gene followed by 15 minutes colonization and then directly sowing in pots. Among three cry genes used, the gene cry2Aa was found most effective showing more transformation frequency.

Agrobacterium tumefaciens-MEDIATED IN PLANTA TRANSFORMATION METHOD FOR THE SoSPS1 GENE IN CITRUS PLANTS (Citrus nobilis L.)

The SoSPS1 gene of sugar cane plants previously subjected to Agrobacterium tumefacienmediated cloning was to be transferred to citrus plants to increase metabolism of sucrose in plant. The T-DNA harbored the SoSPS1 gene under the control of the CaMV 35S promoter from the cauliflower mosaic virus and contained the NPTII gene (kanamycin resistance gene) as a selectable marker for transformant selection. Generally, gene transformation in plants is carried out by tissue culture. However, tissue culture has several disadvantages such as its being time-consuming, its sometimes resulting in somatic mutations and somaclonal variations, and the requirement of sterile conditions in the procedure of gene transfer. In planta transformation is a useful system for those plants that lack tissue culture and regeneration system. The main function of in planta transformation is to recover the advantages of tissue culture as an efficient, quick method, including its ability to produce a large number of transgenic plants and to accumulate a high concentration of total soluble protein in short time. There are two procedures of in planta transformation for the seeds of citrus plants, namely “prick and coat” and “seed tip-cutting and imbibition”. In the prick and coat method, seeds are pricked on their entire surfaces and smeared with a suspension of Agrobacterium tumefaciens. In the seed tip-cutting and imbibition method, on the other hand, seeds are cut at the tip and soaked in a suspension of Agrobacterium tumefaciens. The leaves derived from seeds treatment were taken as samples for DNA extraction and PCR using primers of the NPTII gene (Forward: 5’-GTCATCTCACCTTCCTCCTGCC-3’; Reverse: 5’-GTCGCTTGGTCGGTCATTTCG-3’). This research found that only the seed tip-cutting and imbibition plants amplified along the 550-bp band, while those of the prick and coat method did not. Additionally, the T-DNA was successfully integrated into the genome of the plants treated with the seed tip-cutting and imbibition method but not with the prick and coat.

IN-PLANTA TRANSFORMATION METHOD MEDIATED WITH Agrobacterium tumefaciens FOR T-DNA TRANSFER IN TABLE GRAPE (Vitis vinifera L.)

The aim of the research is to investigate a simple method of in planta transformation method for T-DNA transfer in table grape. The T-DNA harbored the S0SPS1 gene under the control of promoter of the 35S CaMV from the Cauliflower Mosaic Virus and contained the NPTII gene, a kanamycin-resistant gene as a selectable marker for transformant selection. Six-month plants originated from cuttings were used as target plants. We explored two methods of in planta transformation, namely ”dipping” and “sweeping”. For both methods, the leaves of the target plants were removed and those of shoots without leaves were used as the target of transformation. In the “dipping method”, those shoots were dipped with the agrobacterial suspension for 60 seconds. However, for the “sweeping method”, the scars (the spots where leaves were removed) were swept with agrobacterial suspension using a cotton bud. Those treated non-leafy-shoots (from both methods) then were grown to be leafy shoots. Those leafy shoots then were cut and transplanted into the soil and grown to be a whole plant. The leaves of those plants then were taken as samples for DNA extraction and PCR using primers of NPTII gene (Forward: 5’-GTCATCTCACCTTCCTCCTGCC-3’; Reverse: 5’ GTCGCTTGGTCGGTCATTTCG-3’) with expected amplified band of 550 bp. We found that only the “sweeping method” plants amplified the 550 bp bands, while those of the “dipping method” did not. We suggest that the T-DNA was successfully integrated into the genome of plants treated with the “sweeping method” but not with the “dipping method”. Leaf sugar content (oBrix) of PCR-positive vines was higher than those of the wild-type vines, ensuring the integration of the T-DNA into the plant genome.

The effect of magnetic field strength on shoot regeneration and Agrobacterium tumefaciens-mediated gene transfer in flax (Linum usitatissimum L.)

This study was conducted to determine the effects of magnetic field (MF) strength on shoot regeneration and Agrobacterium tumefaciens-mediated gene transfer in flax (Linum usitatissimum L.). Seeds of flax cv. Madaras were exposed to different MF strengths (0 – control, 75, 150, and 300 millitesla (mT)) for 24 h by using an electromagnetic generator system fabricated in laboratory conditions. After sterilization, seeds were germinated on MS (Murashige and Skoog) medium in Magenta vessels. Hypocotyl explants excised from 7-days-old seedlings were used for regeneration. GV2260 strain of Agrobacterium tumefaciens was used in transformation studies. Inoculated hypocotyls were cultured on MS medium containing 1 mg/l BAP (6-benzylaminopurine) and 0.02 mg/l NAA (naphthaleneacetic acid) for 2 days by co-cultivation. Then, they were transferred to MS medium containing the same growth regulators, 100 mg/l kanamycin and 500 mg/l Duocid for selection. The presence of the nptII gene was verified by PCR (polymerase chain reaction) analysis in putative transgenic plants. The highest results with respect to shoot regeneration and transformation frequency were obtained from treatments of 75 mT MF strength.