Somatic and germinal recombination of a direct repeat in Arabidopsis.
Homologous recombination between a pair of directly repeated transgenes was studied in Arabidopsis. The test construct included two different internal, non-overlapping deletion alleles of npt (neomycin phosphotransferase) flanking an active HPT (hygromycin phosphotransferase) gene. This construct was introduced into Arabidopsis by agrobacterium-mediated transformation with selection for resistance to hygromycin, and two independent single-insert lines were analyzed. Selection for active NPT by resistance to kanamycin gave both fully and partly (chimeric) recombinant seedlings. Rates for one transgenic line were estimated at less than 2 x 10(-5) events per division for germinal and greater than 10(-6) events per division for somatic recombination, a much smaller difference than between meiotic and mitotic recombination in yeast. Southern analysis showed that recombinants could be formed by either crossing over or gene conversion. A surprisingly high fraction (at least 2/17) of the recombinants, however, appeared to result from the concerted action of two or more independent simple events. Some evolutionary implications are discussed.
Assaad
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Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
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D000483:Alleles; D017360:Arabidopsis / Q000235:genetics*; D005075:Biological Evolution; D003434:Crossing Over, Genetic; D004247:DNA / Q000235:genetics; D005785:Gene Conversion; D019868:Kanamycin Kinase; D009154:Mutation; D010641:Phenotype; D010770:Phosphotransferases / Q000235:genetics; D017853:Phosphotransferases (Alcohol Group Acceptor); D030821:Plants, Genetically Modified / Q000235:genetics; D010947:Plants, Toxic; D011995:Recombination, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D014026:Nicotiana / Q000235:genetics
D004247:DNA; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C063242:hygromycin-B kinase; D019868:Kanamycin Kinase