Development of Efficient, Reproducible and Stable Agrobacterium-Mediated Genetic Transformation of Five Potato Cultivars

The developments in transformation technology have enabled the scientists to incorporate, mutate or substitute gene(s) leading to a particular trait; advancing it to a point where only few technical limitations remain. Genotype dependency and explant types are important factors affecting transformation efficiency in potato. In the present study, a rapid, reproducible and stable Agrobacterium-mediated transformation procedure in potato was developed by a combination of different plant growth regulators. Leaf discs and internodal explants of five cultivars of potato, i.e. Lady Olympia, Granola, Agria, Désirée and Innovator were infected with Agrobacterium tumefaciens strain LBA4404 containing pBIN19 expression vector with β-glucuronidase gusA gene under the control of 35S CaMV promoter. Kanamycin was used as plant selectable marker for screening of primary transformants at concentration of 100 mg/L. Both explants responded positively; internode being more suitable explant for better transformation efficiency. Based on GUS histochemical assay, the transformation efficiency was 22, 20, 18.6, 15 and 10 % using the internodal explant, and 15, 12, 17, 8 and 6 % using leaf discs as explant in Lady Olympia, Granola, Agria, Désirée and Innovator respectively. Furthermore, PCR assays confirmed the presence of gusA and nptII genes in regenerated plants. The molecular analysis in succeeding progeny showed proper integration and expression of both genes. The results suggest Lady Olympia as the best cultivar for future transformation procedures. Overall, the short duration, rapidity and reproducibility make this protocol suitable for wider application of transgenic potato plants.

Nodulation competitiveness of Ensifer meliloti alfalfa Nodule Isolates and Their Potential for Application as Inoculants

Alfalfa (Medicago sativa) is a widely cultivated legume, which enters into nitrogen-fixing symbiosis with Ensifer (Sinorhizobium) spp. In this study, an autochthonous rhizobial population of Ensifer sp. occupying alfalfa nodules grown in arable soil was used as the basis for selection of potential inoculants. Alfalfa nodule isolates were identified as Ensifer meliloti by partial 16S rDNA, recA, atpD and nodC nucleotide sequencing. The sampled isolates displayed different symbiotic performance and diversity in the number of plasmids and molecular weight. Isolates that were the most efficient in symbiotic nitrogen fixation were tagged with a constitutively expressed gusA gene carried by a stable plasmid vector pJBA21Tc and used in competition experiments in soil under greenhouse conditions. Two E. meliloti strains LU09 and LU12, which effectively competed with indigenous soil rhizobia, were selected. The metabolic profiles of these selected strains showed differences in the use of carbon and energy sources. In addition, the LU09 strain exhibited bacteriocin production and LU12 mineral phosphate solubilization, which are valuable traits for soil survival. These strains may be considered as potential biofertilizers for alfalfa cultivation.

THE USE OF gusA REPORTER GENE TO MONITOR THE SURVIVAL OF INTRODUCED BACTERIA IN THE SOIL

An effective marker to monitor the survival of introduced bacteria in the soil is required for further evaluation of their beneficial effects on plant growth. This study tested the use of gusA gene as a marker to trace the fate of three Gram negative bacteria in the root, rhizosphere, and soil. The study was conducted at the laboratory and greenhouse of the National Institute of Molecular Biology and Biotechnology, Philippines from January to December 2001. Isolates TCaR 61 and TCeRe 60, and Azotobacter vinelandii Mac 259 were selected as test bacteria based on their ability to produce indole-3acetic acid and solubilize precipitated phosphate, which may promote plant growth in the field. These bacteria were marked with gusA reporter gene from Escherichia coli strain S17-1(λ-pir) containing mTn5SSgusA21. The gusA (β-glucuronidase) gene from the donor (E. coli) was transferred to each bacterium (recipient) through bacterial conjugation in mating procedures using tryptone-yeast agar followed by the selection of the transconjugants (bacteria receiving gusA) in tryptone-yeast agar supplemented with double antibiotics and X-GlcA (5bromo-4chloro- 3indoxyl-β-D-glucuronic acid). The antibiotics used were rifampicin and either streptomycin or spectinomycin based on antibiotic profiles of the donor and recipients. The results showed that the insertion of gusA gene into bacterial genomes of the recipient did not impair its phenotypic traits; the growth rates of the transconjugants as well as their ability to produce indole-3acetic acid and solubilize precipitated phosphate in pure culture were similar to their wild types. All transconjugants colonized the roots of hot pepper (Capsicum annuum L.) and survived in the rhizosphere and soil until the late of vegetative growth stage. The distinct blue staining of transconjugants as the expression of gusA gene in media containing X-GlcA coupled with their resistance to rifampicin and streptomycin or spectinomycin made them easier to be recognized and evaluated.<br /><br />

THE USE OF gusA REPORTER GENE TO MONITOR THE SURVIVAL OF INTRODUCED BACTERIA IN THE SOIL

An effective marker to monitor the survival of introduced bacteria in the soil is required for further evaluation of their beneficial effects on plant growth. This study tested the use of gusA gene as a marker to trace the fate of three Gram negative bacteria in the root, rhizosphere, and soil. The study was conducted at the laboratory and greenhouse of the National Institute of Molecular Biology and Biotechnology, Philippines from January to December 2001. Isolates TCaR 61 and TCeRe 60, and Azotobacter vinelandii Mac 259 were selected as test bacteria based on their ability to produce indole-3acetic acid and solubilize precipitated phosphate, which may promote plant growth in the field. These bacteria were marked with gusA reporter gene from Escherichia coli strain S17-1(λ-pir) containing mTn5SSgusA21. The gusA (β-glucuronidase) gene from the donor (E. coli) was transferred to each bacterium (recipient) through bacterial conjugation in mating procedures using tryptone-yeast agar followed by the selection of the transconjugants (bacteria receiving gusA) in tryptone-yeast agar supplemented with double antibiotics and X-GlcA (5bromo-4chloro- 3indoxyl-β-D-glucuronic acid). The antibiotics used were rifampicin and either streptomycin or spectinomycin based on antibiotic profiles of the donor and recipients. The results showed that the insertion of gusA gene into bacterial genomes of the recipient did not impair its phenotypic traits; the growth rates of the transconjugants as well as their ability to produce indole-3acetic acid and solubilize precipitated phosphate in pure culture were similar to their wild types. All transconjugants colonized the roots of hot pepper (Capsicum annuum L.) and survived in the rhizosphere and soil until the late of vegetative growth stage. The distinct blue staining of transconjugants as the expression of gusA gene in media containing X-GlcA coupled with their resistance to rifampicin and streptomycin or spectinomycin made them easier to be recognized and evaluated.<br /><br />

Microspot With Integrated Wells (MSIW) for the Detection of E.coli

There is an increasing problem in getting quality water for developing countries. Water system is contaminated and without proper treatment, it has been consumed as drinking water. It is a big problem for health. Escherichia coli (E.coli) is the main cause for the contamination of water and illness in people. Early detection of E.coli presence in the drinking water followed by subsequent treatment for elimination of E.coli can solve this problem. The present work developed a new method for detecting E.coli in contaminated water using microspot with integrated wells (MSIW). The method involves the fabrication of MSIW, coating the MSIW with enzyme substrates such as 4-MUG substrate (4-Methylumbelliferyl-β-D-glucuronide, trihydrate) and Red-Gal substrate (6-Chloro-3-indolyl-β-D-galactoside) in proper medium and dispensing the contaminated water into MSIW. GlucuronidaseA (gusA) gene in E.coli encodes the beta-D-Glucuronidase (GUS) to hydrolyze the substrate 4-MUG enzymatically which leads to the generation of the fluorigenic compound 4-MU. β-galactosidase enzyme in E.coli produces red color when it reacts with Red-Gal substrate. Using portable optical readers, average color/fluorescence intensity emitting by MSIW is measured and quantified. Comparing obtained intensity values with calibrated intensity values, the level of contamination can be predicted for early warnings.

Transformasi dan Ekspresi Transien Gen Pelapor Gusa pada Andrographis paniculata (Burm.F.) Wallich Ex Ness (Transformation and Expression of Reporter Gene Gusa on Andrographis paniculata (Burm.F.) Wallich Ex Ness)

AbstrakAndrographis paniculata diketahui mengandung senyawa andrografolid, yaitu suatu metabolit sekunder yang memberikan efek farmakologi berupa hepatoprotektif, antiviral dan antikanker. Dalam penelitian ini dilaporkan studi awal prosedur transformasi genetik A. paniculata dengan perantara Agrobacterium tumefaciens. Eksplan daun A. paniculata diinkubasi dengan Ag. tumefaciens strain LBA4404 yang mengandung vektor ganda pCAMBIA1304 dengan gen hpt sebagai gen penanda untuk resistensi higromisin dan gen gusA sebagai gen pelapor. Setelah kokultivasi, eksplan daun dikultur pada medium seleksi yang mengandung higromisin 20 mg L-1 dan sefotaksim 400 mg L-1. Hasil uji histokimia GUS pada potongan daun setelah tiga hari kokultivasi menunjukkan ekspresi transien GUS mencapai 18,83%. Sebanyak 64,44% jaringan A. paniculata yang telah berhasil ditransformasi menunjukkan regenerasi sel dengan menghasilkan kultur kalus transforman pada medium yang mengandung 20 mg/L higromisin.Kata kunci: transformasi genetik, Agrobacterium tumefaciens, Andrographis paniculata, asai GUS.AbstractAndrographis paniculata is known to contain andrographolide, a secondary metabolite which shows pharmacology effects such as hepatoprotective, antiviral and anticancer. We established an Agrobacterium tumefaciens-mediated transformation procedure for A. paniculata. Leaf explants of A. paniculata were incubated with Ag. tumefaciens strain LBA4404 containing a binary vector pCAMBIA1304 with the hpt gene as a selectable marker for hygromycin resistance and an gusA gene as a reporter gene. Following co-cultivation, leaf explants were cultured on selective medium containing 20 mg L-1 hygromycin and 400 mg L-1 cefotaxime. GUS assays showed that only 18.83 % transformation frequency was obtained in leaf disk tissues after 3 days co-cultivation. As much as 64.44 % of the transformed tissue on MS medium containing selection agent 20 mg/L hygromycin showed cell regeneration to produce calluses.Keywords: genetic transformation, Agrobacterium tumefaciens, Andrographis paniculata, GUS assay.

Expression of the DREB1A gene in lentil (Lens culinaris Medik. subsp. culinaris) transformed with the Agrobacterium system

Until now three publications have reported the development of transgenic lentil plants through protocol optimisation using the gusA gene, but there are no reports of the introduction of a gene with agronomic importance. In the present study we report the introduction of the DREB1A gene into lentil to enhance drought and salinity tolerance. Decapitated embryos were immersed in Agrobacterium suspension and then co-cultivated for 4 days. Direct organogenesis was induced from the apical meristems and cotyledonary buds. Subsequently, the explants were subjected to selection in medium containing 10 mg/L phosphinothricin for nine rounds with 2-week intervals. The putative transgenic explants were micro-grafted onto non-transformed rootstocks to establish transgenic plants. The PCR results confirmed the insertion and stable inheritance of the gene of interest and bar marker gene in the plant genome. The Southern blot analysis revealed the integration of a single copy of the transgenes. T0 plants and progeny up to T2 generations showed complete resistance to the herbicide Basta. The DREB1A gene driven by the rd29A promoter was induced in transgenic plants by salt stress from sodium chloride solution. The total RNA was extracted and cDNA synthesised. The results showed that DREB1A mRNA was accumulated and thus the DREB1A transgene was expressed in the transgenic plants, whereas no expression was detected in the non-transformed parents.

Increased metabolic potential of Rhizobium spp. is associated with bacterial competitiveness

Of 105 rhizobial isolates obtained from nodules of commonly cultivated legumes, we selected 19 strains on the basis of a high rate of symbiotic plant growth promotion. Individual strains within the species Rhizobium leguminosarum bv. trifolii , R. leguminosarum bv. viciae , and Rhizobium etli displayed variation not only in plasmid sizes and numbers but also in the chromosomal 16S–23S internal transcribed spacer. The strains were tagged with gusA gene and their competitiveness was examined in relation to an indigenous population of rhizobia under greenhouse conditions. A group of 9 strains was thus isolated that were competitive in relation to native rhizobia in pot experiments. Nineteen selected competitive and uncompetitive strains were examined with respect to their ability to utilize various carbon and energy sources by means of commercial Biolog GN2 microplate test. The ability of the selected strains to metabolize a wide range of nutrients differed markedly and the competitive strains were able to utilize more carbon and energy sources than uncompetitive ones. A major difference concerned the utilization of amino and organic acids, which were metabolized by most of the competitive and only a few uncompetitive strains, whereas sugars and their derivatives were commonly utilized by both groups of strains. A statistically significant correlation between the ability to metabolize a broad range of substrates and nodulation competitiveness was found, indicating that metabolic properties may be an essential trait in determining the competitiveness of rhizobia.