Efficient Agrobacterium-mediated Transformation Protocol Research Articles

Agrobacterium-Mediated Transformation of the Dwarf Soybean MiniMax.

This study aims to establish an Agrobacterium-mediated transformation system for use with the 'MiniMax'soybean cultivar. MiniMax is a mutant soybean whose growth cycle is around 90 days, half that of most other soybean varieties, making it an optimal model cultivar to test genes of interest before investing in modification of elite lines. We describe an efficient protocol for Agrobacterium-mediated transformation using MiniMax seeds. It uses a modified 'half seed' regeneration protocol for transgenic soybean production, utilizing the rapid generation MiniMax variety to obtain T1 seeds in approximately 145 days. Addition of phloroglucinol (PG) to the regeneration protocol was key to obtaining high-efficiency rooting of the regenerated shoots. Transfer to soil was accomplished using an organic soil amendment containing nutrients and mycorrhiza for plants to thrive in the greenhouse. This combination of genotype and stimulants provides a transformation protocol to genetically engineer MiniMax seeds with a transgenic lab-to-greenhouse production efficiency of 4.0%. This is the first report of MiniMax soybean whole plant transformation and heritable T1 transmission. This protocol provides an ideal resource for enhancing the genetic transformation of any soybean cultivar.

An Efficient Protocol for Agrobacterium-Mediated Transformation and Regeneration of Sugar Beet (Beta vulgaris L.) based on Blade–Petiole Transition Zone Explants

An Efficient Protocol for Agrobacterium-Mediated Transformation and Regeneration of Sugar Beet (Beta vulgaris L.) based on Blade–Petiole Transition Zone Explants

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.

An efficient Agrobacterium-mediated transformation method using hypocotyl as explants for Brassica napus

Rapeseed (Brassica napus) is an important oil crop that supplies a considerable amount of global vegetable oil production. Genetic transformation system is important to gene functional analysis and molecular breeding. Here, an efficient Agrobacterium-mediated transformation protocol using hypocotyl of rapeseed as explants is described. To develop this protocol, we compared several essential factors that would affect the transformation efficiency, such as Agrobacterium strains, selection marker genes, and genotypes of rapeseed. Comparison of different Agrobacterium strains showed that the GV3101 had higher transformation efficiency than that of C58C1 and EHA105. HPTII, NPTII, and RePAT were used as selection marker genes in tissue culture. The results showed that the transformation efficiency was 3.7–4.8%, 2.2–22.5%, and 1.6–5.9% when the hypocotyl of Westar was infected by GV3101 and screened under hygromycin, kanamycin, and basta, respectively. The transformation efficiency of Westar was the highest and ZS11 was the lowest when five different genotypes of rapeseed (Westar, ZS9, ZS11, GY284, and WH3417) were infected by GV3101. Using this protocol, it will take 8–10 weeks to obtain transgenic plants. This protocol has been used to study gene function in several genotypes of rapeseed in our laboratory. These results indicate that it is efficient to obtain transgenic plant of rapeseed using this protocol.

An efficient protocol for Agrobacterium-mediated transformation and regeneration of Campanula medium (Canterbury bells) based on leaf disc explants

Campanula medium is an important ornamental plant known for its blue and bell-shaped flowers and a good model for studying flower colour formation and modification. The major outstanding obstacle preventing the developing of genetic modification and improvements in C. medium is a missing transformation method. For the first time, an effective and reliable in vitro regeneration and Agrobacterium-mediated transformation system has been established in this study. Different types and combinations of plant growth regulators (PGRs) were investigated for shoot regeneration by using leaf explants from three different cultivars. A high regeneration rate (50% for cv. ‘Blue double’, 58% for cv. ‘White double’ and 44% for cv. ‘Pink double’) was achieved on MS-based medium supplemented with 11.5 μM thidiazuron (TDZ) and 2.3 μM 1-naphthaleneacetic acid (NAA). In total, the Agrobacterium strains ABI, AGL1 and GV3101:pMP90, transformed with a binary plasmid harbouring NPTII and GFP gene cassettes, were evaluated for plant transformation, while various factors affecting the transformation efficiency were also identified. The highest transformation rate of about 22% was obtained from explants pre-cultured on regeneration medium and infected with AGL1. However, transgenic shoots were produced by all three Agrobacterium strains studied and confirmed by PCR and GFP fluorescence microscopy. Campanula medium regeneration and genetic transformation methods were established while various factors affecting the transformation efficiency were identified such as pre-culture treatment of leaf explants and different Agrobacterium strains.

Development of a rapid and highly efficient Agrobacterium-mediated transformation system for pigeon pea [Cajanus cajan (L.) Millsp

ABSTRACTAn efficient genetic transformation system is a prerequisite for studying gene functions, molecular breeding program, and introducing new traits. Agrobacterium tumefaciens-mediated genetic transformation is a widely preferred and accepted method for many plants, including pigeon pea. However, the efficiency of transformation of pigeon pea using the existing protocols is low and time-consuming. In the present study, we developed a rapid and highly efficient transformation system of pigeon pea, using embryonic axis-attached cotyledons as explants. We systematically investigated the influence of varying optical densities of Agrobacterium suspension, duration of incubation, and co-cultivation on the transformation efficiency. In our system, a transformation efficiency of approximately 83% was achieved using Agrobacterium cells at an optical density (OD600) of 0.25, infection time of 15 min, and co-culturing with explants for 72 h in the light with 100µM acetosyringone. The entire procedure, starting from seed to establishment of transformed plants in soil, was achieved in 35–40 days. This is a rapid and highly efficient protocol for Agrobacterium-mediated transformation of pigeon pea, which could potentially be a useful reference, not only for the genetic improvement of pigeon pea but also for other recalcitrant leguminous plants.

An Efficient Protocol for Agrobacterium-mediated Transformation of Sugarcane by Optimizing of Duration of Co-cultivation and Age of Callus

An Efficient Protocol for Agrobacterium-mediated Transformation of Sugarcane by Optimizing of Duration of Co-cultivation and Age of Callus

Evaluation of Factors Impacting Agrobacterium-Mediated Indica Rice Transformation of IR58025B - a Public Maintainer Line

n this study, we report our efforts to develop an efficient Agrobacterium-mediated transformation protocol for the transformation of Indica rice IR58025B with mannose as a selection agent. Various factors, such as basal medium, culture temperature, strains for infection, air-drying duration of calli after infection, and salt concentration of coculture medium, were systematically optimized so that the highest transformation frequency (TF) reached to 74%. About 94% of mature embryos were induced to generate calli of high quality on modified NB medium. Both callus quantity and quality were improved when callus was induced from endosperm-free embryos in comparison to intact mature seeds. Higher temperature (32°C) showed improvements when compared to lower temperatures at (25°C and 28°C) for both callus induction and transformation. Agrobacterium strains of EHA105 produced the best TF in comparison with EHA101, LBA4404 and AGL1. However, LBA4404 produced the highest single copy frequency. Prior to co-cultivation, air-drying of inoculated calli was performed in a laminar flow hood for 4-7 hours and produced a higher TF. Lower salt concentration for co-cultivation medium enhanced both DNA delivery and TF.

Factors Affecting in Vitro Shoot Regeneration in Hypocotyls of Brinjal (Solanum melongena L.) in the Early Steps of Agrobacterium-Mediated Transformation

An attempt was made to assess the effect of size, age and position of the explant, pre-culture and high cytokinin concentration in the pre-culture medium on shoot regeneration in brinjal hypocotyls co-cultivated with Agrobacterium. The study was carried out using hypocotyl explants of brinjal cv. Manjarigota, Agrobacterium strain A208 and shoot regeneration medium (full-strength basal MS medium, 2μM BAP + 0.05μM NAA, 3% sucrose and 0.8% agar) containing Cefotaxime (250-500mg l-1) and Kanamycin (100mg l-1). Hypocotyl explants showed callus initiation and shoot regeneration response after 10-12 and 20-22 days of culture, respectively. Five-day-old explants did not survive Agrobacterium infection, and ten-day-old explants showed higher shoot regeneration (29±1.91%) than older explants. Explants of medium size (1cm long; 32±2.62%) from the apical region (38.57±2.61%) showed better shootregeneration ability than explants of any other size or region. A period of four days of pre-culture (33.33±3.76) was optimal best for best shoot-regeneration in hypocotyl explants. No regeneration was seen in hypocotyl explants at shorter or longer pre-culture period. High cytokinin (10μM) in shoot regeneration medium during pre-culture enhanced shoot regeneration response (47.27±2.98%) in explants co-cultivated with Agrobacterium. Effects of various factors documented in this study will be useful in developing an efficient Agrobacterium-mediated transformation protocol in brinjal cv. Manjarigota.

An efficient protocol for Agrobacterium-mediated transformation of the biofuel plant Jatropha curcas by optimizing kanamycin concentration and duration of delayed selection.

Jatropha curcas is considered a potential biodiesel feedstock crop. Currently, the value of J. curcas is limited because its seed yield is generally low. Transgenic modification is a promising approach to improve the seed yield of J. curcas. Although Agrobacterium-mediated genetic transformation of J. curcas has been pursued for several years, the transformation efficiency remains unsatisfying. Therefore, a highly efficient and simple Agrobacterium-mediated genetic transformation method for J. curcas should be developed. We examined and optimized several key factors that affect genetic transformation of J. curcas in this study. The results showed that the EHA105 strain was superior to the other three Agrobacterium tumefaciens strains for infecting J. curcas cotyledons, and the supplementation of 100 mM acetosyringone slightly increased the transient transformation frequency. Use of the appropriate inoculation method, optimal kanamycin concentration and appropriate duration of delayed selection also improved the efficiency of stable genetic transformation of J. curcas. The percentage of β-glucuronidase positive J. curcas shoots reached as high as 56.0 %, and 1.70 transformants per explant were obtained with this protocol. Furthermore, we optimized the root-inducing medium to achieve a rooting rate of 84.9 %. Stable integration of the T-DNA into the genomes of putative transgenic lines was confirmed by PCR and Southern blot analysis. Using this improved protocol, a large number of transgenic J. curcas plantlets can be routinely obtained within approximately 4 months. The detailed information provided here for each step of J. curcas transformation should enable successful implementation of this transgenic technology in other laboratories.Electronic supplementary materialThe online version of this article (doi:10.1007/s11816-015-0377-0) contains supplementary material, which is available to authorized users.

Agrobacterium-mediated in planta genetic transformation of sugarcane setts.

An efficient, reproducible, and genotype-independent in planta transformation has been developed for sugarcane using setts as explant. Traditional Agrobacterium-mediated genetic transformation and in vitro regeneration of sugarcane is a complex and time-consuming process. Development of an efficient Agrobacterium-mediated transformation protocol, which can produce a large number of transgenic plants in short duration is advantageous. Hence, in the present investigation, we developed a tissue culture-independent in planta genetic transformation system for sugarcane using setts collected from 6-month-old sugarcane plants. The sugarcane setts (nodal cuttings) were infected with three Agrobacterium tumefaciens strains harbouring pCAMBIA 1301-bar plasmid, and the transformants were selected against BASTA(®). Several parameters influencing the in planta transformation such as A. tumefaciens strains, acetosyringone, sonication and exposure to vacuum pressure, have been evaluated. The putatively transformed sugarcane plants were screened by GUS histochemical assay. Sugarcane setts were pricked and sonicated for 6min and vacuum infiltered for 2min at 500mmHg in A. tumefaciens C58C1 suspension containing 100µM acetosyringone, 0.1% Silwett L-77 showed the highest transformation efficiency of 29.6% (with var. Co 62175). The three-stage selection process completely eliminated the chimeric transgenic sugarcane plants. Among the five sugarcane varieties evaluated using the standardized protocol, var. Co 6907 showed the maximum transformation efficiency (32.6%). The in planta transformation protocol described here is applicable to transfer the economically important genes into different varieties of sugarcane in relatively short time.

A simple and highly efficient Agrobacterium-mediated transformation protocol for Setaria viridis

The production and use of sugarcane in Brazil is very important for bioenergy production and is recognized as one of the most efficient in the world. In our laboratory, Setaria viridis is being tested as a model plant for sugarcane. S. viridis has biological attributes (rapid life cycle, small genome, diploid, short stature and simple growth requirements) that make it suitable for use as a model system. We report a highly efficient protocol for Agrobacterium-mediated genetic transformation of S. viridis. The optimization of several steps in tissue culture allowed the rapid regeneration of plants and increased the rate of transformation up to 29%. This protocol could become a powerful tool for functional genomics in sugarcane.

Evaluation of factors influencing Agrobacterium-mediated spinach transformation and transformant selection by EGFP fluorescence under low-selective pressure

We developed an efficient Agrobacterium-mediated transformation protocol for spinach (Spinacia oleracea L.) that uses root-derived callus. Evaluation of this protocol was based on the systematic evaluation of factors that influence transformation efficiency. Four of the five factors that were tested significantly affected the transformation efficiency, including spinach cultivar, Agrobacterium tumefaciens strain and density, and the duration of co-cultivation. Transgenic spinach plants were generated based on optimized conditions, consisting of callus explants of the cultivar Gyeowoonae, A. tumefaciens strain EHA105 with OD600 of 0.2, a co-cultivation period of 4 d, and 100 μM acetosyringone supplemented in the inoculation and co-cultivation media. After co-cultivation with A. tumefaciens, explants were cultured in low-selective and then non-selective conditions to enhance the growth of putative transgenic explants. Visualization of the fluorescent marker, enhanced green fluorescent protein (EGFP), was used to select transgenic explants at several stages, including callus, somatic cotyledonary embryo, and plantlet. The best results for fluorescence visualization screening were obtained at the somatic cotyledonary embryo stage. On average, 24.96 ± 6.05% of the initial calli regenerated shoots that exhibited EGFP fluorescence. The putative transgenic plants were subjected to β-glucuronidase (GUS)-staining assay, phosphinothricin acetyltransferase (PAT) strip test, and molecular analyses to assess the transgene incorporation into plant genome and its expression. All EGFP-positive plants tested were confirmed to be transgenic by GUS-staining assay, PAT strip test, and molecular analyses. The transformation system described in this study could be a practical and powerful technique for functional genetic analysis and genetic modification of spinach.

Vacuum infiltration enhances the Agrobacterium-mediated genetic transformation in Indian soybean cultivars

For the first time we have developed a reliable and efficient vacuum infiltration-assisted Agrobacterium-mediated genetic transformation (VIAAT) protocol for Indian soybean cultivars and recovered fertile transgenic soybean plants through somatic embryogenesis. Immature cotyledons were used as an explant and three Agrobacterium tumefaciens strains (EHA 101, EHA 105, and KYRT 1) harbouring the binary vector pCAMBIA1301 were experimented in the co-cultivation. The immature cotyledons were pre-cultured in liquid somatic embryo induction medium prior to vacuum infiltration with the Agrobacterium suspension and co-cultivated for 3 days on co-cultivation medium containing 50 mg l−1 citric acid, 100 µM acetosyringone, and 100 mg l−1 l-cysteine. The transformed somatic embryos were selected in liquid somatic embryo induction medium containing 10 mg l−1 hygromycin and the embryos were germinated in basal medium containing 20 mg l−1 hygromycin. The presence and integration of the hpt II and gus genes into the soybean genome were confirmed by GUS histochemical assay, polymerase chain reaction, and Southern hybridization. Among the different combinations tested, high transformation efficiency (9.45 %) was achieved when immature cotyledons of cv. Pusa 16 were pre-cultured for 18 h and vacuum infiltrated with Agrobacterium tumefaciens KYRT 1 for 2 min at 750 mm of Hg. Among six Indian soybean cultivars tested, Pusa 16 showed highest transformation efficiency of 9.45 %. The transformation efficiency of this method (VIAAT) was higher than previously reported sonication-assisted Agrobacterium-mediated transformation. These results suggest that an efficient Agrobacterium-mediated transformation protocol for stable integration of foreign genes into soybean has been developed.

Agrobacterium-mediated transformation of cotyledons of mature seeds of multiple genotypes of sunflower (Helianthus annuus L.)

Lack of a genotype-independent transformation protocol for sunflower is a major bottleneck in improving this important oilseed crop. An efficient Agrobacterium-mediated transformation protocol is described, which was adaptable across a broad range of sunflower genotypes. The improved transformation approach used cotyledons from mature seeds vertically split through the embryo axis. The LBA 4404 Agrobacterium strain was used, which carried pCAMBIA 2301 plasmid containing UidA as the reporter gene and nptII as the selectable marker for transformants on kanamycin. Bacterial titer, cotyledon type, acetosyringone concentration and vacuum application enhanced the transformation efficiency. Wounding, enzyme pretreatment and sonication significantly reduced the transformation frequency. Putative transgenic shoots were obtained through both axillary proliferation and adventitious shoot regeneration. Following two and three cycles of selection on kanamycin for axillary and adventitious shoots, respectively, putative transformed shoots were obtained at an average frequency of 3.0 %. Reporter gene histochemical assay and molecular characterization of primary and T1 transgenic plants revealed stable transgene integration, expression and monogenic inheritance. The standardized procedure was tested on 28 genotypes comprising sets of inbred, maintainer, restorer and hybrid lines. Transformation was successful in all genotypes albeit with variable frequency in all except the hybrid lines wherein it was stable around 4.0 %. The procedure opens possibilities of directly improving any commercial genotypes of sunflower.

An efficient Agrobacterium-mediated transformation protocol for black pepper (Piper nigrum L.) using embryogenic mass as explant

A protocol was developed for an efficient Agrobactertium-mediated transformation of black pepper plants through somatic embryogenesis. Embryogenic mass derived from primary somatic embryos that were obtained from the micropylar region of mature germinating seeds of black pepper was found to be the ideal target tissue for transformation. Genetic fidelity test of embryogenic mass-derived plantlets by RAPD using 23 random primers revealed no genetic variation among the progenies and the parent plant. Among the antibiotics used for selection of transformants, cefotaxime at 100 μg mL−1 was found to be optimum to control Agrobacterium besides its ability to promote somatic embryo proliferation. In the case of kanamycin, a step-wise increase in concentration from 25 to 50 and then to 100 μg mL−1 were found to be optimum. Embryogenic mass co-cultivated with Agrobacterium carrying the β-glucuronidase (GUS) reporter gene were cultured on plant growth regulator-free Schenk and Hildebrandt (SH) medium and transformants were selected in selection medium containing cefotaxime and step-wise increase in kanamycin concentration. The transient GUS gene expression was determined histochemically. Transformants that survived in the selection medium were hardened in the greenhouse. An average of nine hardened putative plantlets was obtained per gram of embryogenic mass. The presence of transgene in these plantlets was assayed by PCR, dot blot, and Southern blot hybridization. Results presented demonstrated for the first time an efficient transformation and regeneration of black pepper without the use of growth regulators. This simple efficient procedure would allow transformation of black pepper with genes of desirable characters.

Highly efficient Agrobacterium-mediated transformation of banana cv. Rasthali (AAB) via sonication and vacuum infiltration

A reproducible and efficient transformation method was developed for the banana cv. Rasthali (AAB) via Agrobacterium-mediated genetic transformation of suckers. Three-month-old banana suckers were used as explant and three Agrobacterium tumefaciens strains (EHA105, EHA101, and LBA4404) harboring the binary vector pCAMBIA1301 were used in the co-cultivation. The banana suckers were sonicated and vacuum infiltered with each of the three A. tumefaciens strains and co-cultivated in the medium containing different concentrations of acetosyringone for 3 days. The transformed shoots were selected in 30 mg/l hygromycin-containing selection medium and rooted in rooting medium containing 1 mg/l IBA and 30 mg/l hygromycin. The presence and integration of the hpt II and gus genes into the banana genome were confirmed by GUS histochemical assay, polymerase chain reaction, and southern hybridization. Among the different combinations tested, high transformation efficiency (39.4 ± 0.5% GUS positive shoots) was obtained when suckers were sonicated and vacuum infiltered for 6 min with A. tumefaciens EHA105 in presence of 50 μM acetosyringone followed by co-cultivation in 50 μM acetosyringone-containing medium for 3 days. These results suggest that an efficient Agrobacterium-mediated transformation protocol for stable integration of foreign genes into banana has been developed and that this transformation system could be useful for future studies on transferring economically important genes into banana.

Agrobacterium-mediated transformation of two Serbian potato cultivars (Solanum tuberosum L. cv. Dragačevka and cv. Jelica)

An efficient protocol for Agrobacterium-mediated transformation of Serbian potato cultivars Draga
evka and Jelica, enabling the introduction of oryzacystatin genes OCI and OCII, was established. Starting with leaf explants, a two-stage transformation protocol combining procedures of Webb and Wenzler provided high shoot regeneration efficiency: 84 - 89% for Draga
evka cultivar and 60 - 68% for Jelica cultivar as compared to 76 - 86% for Desiree, the most frequently used cultivar in transformation experiments. PCR analysis of a small sample of putative transformants showed a nptII integration frequency of 90.9, 76.9 and 86.4% for Draga
evka, Jelica and Desiree, respectively. Regeneration and transformation efficiency was strongly genotype-dependent.

Agrobacterium-mediated transformation of Brassica napus and Brassica oleracea

Agrobacterium-mediated transformation is widely used for gene delivery in plants. However, commercial cultivars of crop plants are often recalcitrant to transformation because the protocols established for model varieties are not directly applicable to them. The genus Brassica includes the oil seed crop, canola (B. napus), and vegetable crop varieties of Brassica oleracea, including cauliflower, broccoli and cabbage. Here, we describe an efficient protocol for Agrobacterium-mediated transformation using seedling explants that is applicable to various Brassica varieties; this protocol has been used to genetically engineer commercial cultivars of canola and cauliflower in our laboratory. Young seedling explants are inoculated with Agrobacterium on the day of explant preparation. Explants are grown for 1 week in the absence of a selective agent before being transferred to a selective medium to recover transgenic shoots. Transgenic shoots are subjected to an additional round of selection on medium containing higher levels of the selective agent and a low-carbohydrate source; this helps to eliminate false-positive plants. Use of seedling explants offers flexible experiment planning and a convenient explant source. Using this protocol, transgenic plants can be obtained in 2.5 to 3.5 months.

Agrobacterium-mediated transformation and generation of male sterile lines of Australian canola

An efficient protocol for Agrobacterium-mediated transformation of Australian commercial canola cultivars using seedling explants is described. Seedling explants provide flexibility and reduction in labour and maintenance costs of explant sources. Five commercial genotypes of canola were successfully transformed using the developed protocol. A transformation efficiency of 67% was obtained for genotypes Oscar and RK7 from cotyledon explants, which was higher than the rate for the most commonly used cultivar Westar (33%). Comparison of different seedling explants showed that although transgenic plants could be regenerated from all explant types (cotyledons, hypocotyls, and roots) used, the number of plants regenerated per explant type varied among the cultivars. Cotyledons produced the maximum number of transgenic shoots (RK7, RI25, Oscar, and Westar cultivars), whereas root explants produced the lowest numbers of shoots. Therefore, cotyledons and hypocotyls can be considered as ideal explants for the Agrobacterium-mediated transformation of these Australian canola cultivars. Integration and expression of the introduced transgene were analysed by DNA gel blot, leaf disc test, and GUS expression assays. Analysis of progeny showed that the transgene was stably inherited. The possibility of producing male sterile lines using an antisense approach was also explored. For this, Bcp1, a gene shown to be vital for viable pollen development, was targetted. Pollen ablation and lack of seed set were observed in the transgenic plants. Histochemical tests showed an intact tapetum layer and well developed pollen in control plants, whereas degraded tapetum and ablated pollen were noted in the transgenic plants. These results indicate that it is possible to generate stable transgenic male-sterile lines of canola using this strategy.