Transgenic mimicry of pathogen attack stimulates growth and secondary metabolite accumulation.

Plant secondary metabolites, including pharmaceuticals, flavorings and aromas, are often produced in response to stress. We used chemical inducers of the pathogen defense response (jasmonic acid, salicylate, killed fungi, oligosaccharides and the fungal elicitor protein, cryptogein) to increase metabolite and biomass production in transformed root cultures of the medicinal plant, Withania somnifera, and the weed, Convolvulus sepium. In an effort to genetically mimic the observed effects of cryptogein, we employed Agrobacterium rhizogenes to insert a synthetic gene encoding cryptogein into the roots of C. sepium, W. somnifera and Tylophora tanakae. This genetic transformation was associated with stimulation in both secondary metabolite production and growth in the first two species, and in growth in the third. In whole plants of Convolvulus arvensis and Arabidopsis thaliana, transformation with the cryptogein gene led, respectively, to increases in the calystegines and certain flavonoids. A similar transgenic mimicry of pathogen attack was previously employed to stimulate resistance to the pathogen and abiotic stress. In the present study of biochemical phenotype, we show that transgenic mimicry is correlated with increased secondary metabolite production in transformed root cultures and whole plants. We propose that natural transformation with genes encoding the production of microbial elicitors could influence interactions between plants and other organisms.

Spontaneous plant regeneration in transformed roots and calli from Tylophora indica: Changes in morphological phenotype and tylophorine accumulation associated with transformation by Agrobacterium rhizogenes.

We examined the effects of genetic transformation by Agrobacterium rhizogenes on the production of tylophorine, a phenanthroindolizidine alkaloid, in the Indian medicinal plant, Tylophora indica. Transformed roots induced by the bacterium grew in axenic culture and produced shoots or embryogenic calli in the absence of hormone treatments. However, hormonal treatment was required to regenerate shoots in root explants of wild type control plants. Transformed plants showed morphological features typically seen in transgenic plants produced by A. rhizogenes, which include, short internodes, small and wrinkled leaves, more branches and numerous plagiotropic roots. Plants regenerated from transformed roots showed increased biomass accumulation (350-510% in the roots and 200-320% in the whole plants) and augmented tylophorine content (20-60%) in the shoots, resulting in a 160-280% increase in tylophorine production in different clones grown in vitro.

Genetic transformation of Tylophora indica with Agrobacterium rhizogenes A4: growth and tylophorine productivity in different transformed root clones.

We have developed an efficient transformation system for Tylophora indica, an important medicinal plant in India, using Agrobacterium rhizogenes strains LBA9402 and A4 to infect excised leaf and stem explants and intact shoots at different sites. The induction of callus and transformed roots was dependent on the bacterial strain, explant type and inoculation site used. Transformed roots were induced only in explants infected with A. rhizogenes strain A4, while an optimal transformation frequency of up to 60% was obtained with intact shoots inoculated at the nodes. The presence of the left-hand transferred DNA (T(L)-DNA) in the genome of T. indica roots induced by A. rhizogenes was confirmed by PCR amplification of the rooting locus genes of A. rhizogenes. Root growth and the production of tylophorine, the major alkaloid of the plant, varied substantially among the nine root clones studied. Both parameters increased over time in liquid cultures, with maximum biomass and tylophorine accumulation occurring within 4-6 weeks of growth in fresh medium. Interestingly, in liquid culture, the culture medium also accumulated tylophorine up to concentrations of 9.78+/-0.21 mg l(-1).

Childhood malignancies at BS Medical College: a ten year study.

A retrospective study of malignant diseases of childhood was carried out at B. S. Medical College, Bankura, W.B. to know the prevalence. It includes cases detected in this institution during 1990-1999 in the age group of 0-14 years. Cases were identified from previous records. Histopathology slides, stained by hematoxylin and eosin, were recovered and reviewed. Diagnosis were made by morphology. Hematological diagnosis were made by morphology and cyto-chemistry. In total 120 cases were detected. Acute leukemia (39.2%) was the commonest, followed by retinoblastoma (19.2%), lymphoma (10.8%), Wilm's tumor (10%) and rhabdomyosarcoma (9.1%). Brain tumors were not found due to non-availability of Neurosurgical Unit in this institution. Frequency of neuroblastoma was very low, only 2 out of a total of 120. In comparison to studies in Southern India and Western countries retinoblastoma and soft tissue sarcoma are more prevalent here, while there is a much lower prevalence of neuroblastoma.