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451.
452.
Comparison of homologous recombination frequencies in somatic cells of petunia and tobacco suggest two distinct recombination pathways 总被引:1,自引:0,他引:1
Homologous recombination in plants was studied using an extrachromosomal recombination assay in which intermolecular homologous recombination between two complementary plasmids restored a selectable marker gene. Several vectors containing an insertion into or deletions within the coding region of the neomycin phosphotransferase (NPT-II) gene were designed. Plasmids were introduced, in pairwise combinations, into protoplasts and homologous recombination events were measured by counting the number of NPT-ll-resistant colonies. A 10-fold increase in recombination frequency was observed in Petunia hybrids RL01 compared to Nicotiana tabacum SRI. This difference occurred when one or both of the co-transferred recombination plasmids was offered in a circular form. Apart from such specific differences between two cultivars from different species, a two-to fivefold increase in recombination frequencies was observed when the genomic TBS (transformation booster sequence) fragment from P. hybrids was added onto one of the transferred plasmids. TBS-specific stimulation of recombination was observed in Petunia RL01. These data suggest that two different recombination pathways may be present in plants. 相似文献
453.
454.
J W Engels T Daum A Frauendorf S Lüking M Mag W E Müller J Muth P Rosmanitz 《Nucleic acids symposium series》1991,(24):83-86
Oligonucleotides bearing phosphorothioate linkages of the HIV tatIII splice acceptor site were synthesized by automated solid phase synthesis. Especially 5'- and 3'-end capped thioates of the sequence 5'-ACACCCAATTCTGAAAATGG-3' show microM inhibition of HIV replication. ODN-methylphosphonates of defined stereochemistry were obtained with suitably modified proline phosphonamidite derivatives as monomeric building blocks. Asymmetric induction for nucleosidephosphonamidates up to 5:1 (Rp:Sp rsp. Sp:Rp depending on configuration of proline-moiety) could be reached. The intermediate phosphonamidite can be further reacted to dinucleoside methylphosphonates of enriched diastereomeric excess. 相似文献