No abstract

Most of the S. spinosa genes involved in spinosyn biosynthesis are found in one 74 kb cluster, though it does not contain all of the genes required for the essential deoxysugars. Characterization of the clustered genes suggests that the spinosyns are synthesized largely by mechanisms similar to those used to assemble complex macrolides in other actinomycetes. However, there are several unusual genes in the spinosyn cluster that could encode enzymes that generate the most striking structural feature of these compounds, a tetracyclic polyketide aglycone nucleus.

Sequences coding for the bean seed protein phaseolin were inserted into transferred DNA regions of tumor-inducing plasmids. Constructions were devised in which the coding region of phaseolin was fused in the correct reading frame with the coding region of octopine synthase and placed under the transcriptional control of the octopine synthase promoter. Other plasmids were prepared to permit expression of the phaseolin-encoding sequences from the flanking phaseolin promoter region. The RNA transcribed in sunflower cells transformed with these constructions was characterized by hybridization procedures, SI nuclease mapping, and by translation in vitro of extracted RNA. These tests showed that the genomic intervening sequences were correctly excised. Immunoreactive phaseolin polypeptides were detected by enzyme-linked immunosorbent assay and by antibody hybridization to electrophoretically separated protein extracts of sunflower tissues isolated from crown gall tumors and of transformed sunflower cells grown in tissue culture. These results demonstrate the expression of a plant gene after transfer to a taxonomically distinct botanical family.

Cotton (Gossypium hirsutum L.) cotyledon tissues have been efficiently transformed and plants have been regenerated. Cotyledon pieces from 12-day-old aseptically germinated seedlings were inoculated with Agrobacterium tumefaciens strains containing avirulent Ti (tumor-inducing) plasmids with a chimeric gene encoding kanamycin resistance. After three days cocultivation, the cotyledon pieces were placed on a callus initiation medium containing kanamycin for selection. High frequencies of transformed kanamycin-resistant calli were produced, more than 80% of which were induced to form somatic embryos. Somatic embryos were germinated, and plants were regenerated and transferred to soil. Transformation was confirmed by opine production, kanamycin resistance, immunoassay, and DNA blot hybridization. This process for producing transgenic cotton plants facilitates transfer of genes of economic importance to cotton.

Agrobacterium‐mediated transfer from a binary vector was used to produce transgenic Nicotiana tabacum plants that expressed coat protein of the plant virus, alfalfa mosaic virus (AMV). Expression levels of the chimeric gene, which was under the control of the cauliflower mosaic virus 19S promoter, were determined in primary transformed plants, in the progeny from self‐fertilization and in the progeny from crosses to normal tobacco. RNA transcripts that were of the expected size as well as a protein of the Mr and antigenicity of AMV coat protein accumulated in the transgenic plants. Plants that expressed the highest levels of coat protein developed fewer primary infections following inoculation with two strains of AMV and developed systemic infection slower than did plants that did not express coat protein. Resistance was specifically against virions of the AMV strains. AMV RNA and the unrelated virus, tobacco mosaic virus, were as infectious on progeny that expressed coat protein as they were on progeny that did not. The relationship between the virus resistance expressed by these transgenic plants and that observed in virus cross‐protection is discussed.