Rice Genetics IV - IRRI books - International Rice Research Institute

Mutants identified by this method are being characterized for their phenotypesand some showed clear phenotypes. For example, one mutant line was shown to carrythe Tos17 insertion in the gene with a significant homology to a RING finger gene.This gene is new in rice and is thus named OSRING1. Diverse important functions ofRING finger genes have been reported in yeast, nematode, Drosophila, and mammals(Saurin et al 1996), such as oncogenesis, signal transduction, and biogenesis of peroxisome.However, because the functions of plant RING finger genes are not knownexcept for COP1 (Torii et al 1998), we started the functional analysis of the OSRING1gene. The mutant showed deficiency in lateral root development. Introducing the 5.3-kb genomic fragment containing the entire ORF driven by the 35S promoter couldcomplement the mutant phenotype, confirming that it is caused by the disruption ofOSRING1. Further analysis showed that OSRING1 negatively regulates ethylene productionand thus controls cell elongation during lateral root development.In summary, these results indicate that the strategy described in this section isfeasible and applicable to the genome-wide screening of mutants. Another importantresult obtained by the analysis of the flanking sequences is that the ends of transposedTos17 copies are intact. In contrast, rearrangements of terminal regions of T-DNA areinduced quite often (Castle et al 1993, Krysan et al 1999). No induction of rearrangementsof the Tos17 ends makes it easy to isolate flanking sequences and screen formutants by PCR.ReferencesAzpiroz-Leehan R, Feldmann KA. 1997. T-DNA insertion mutagenesis in Arabidopsis: goingback and forth. Trends Genet. 13:152-156.Ballinger DG, Benzer S. 1989. Targeted gene mutations in Drosophila. Proc. Natl. Acad. Sci.USA 86:9402-9406.Bancroft I, Jones JDG, Dean C. 1993. Heterologous transposon tagging of the DRL1 locus inArabidopsis. Plant Cell 5:631-638.Bensen RJ, Johal GS, Crane VC, Tossberg JT, Schnable PS, Meeley RB, Briggs SP. 1995.Cloning and characterization of the maize An1 gene. Plant Cell 7:75-84.Bevan M and 67 others. 1998. Analysis of 1.9 Mb of contiguous sequence from chromosome 4of Arabidopsis thaliana. Nature 391:485-488.Brettell RIS, Dennis ES, Scowcroft WR, Peacock WJ. 1986. Molecular analysis of a somaclonalmutant of maize alcohol dehydrogenase. Mol. Gen. Genet. 202:235-239.Castle LA, Errampalli D, Atherton TL, Franzmann LH, Yoon ES, Meinke DW. 1993. Geneticand molecular characterization of embryonic mutants identified following seed transformationin Arabidopsis. Mol. Gen. Genet. 241:504-514.Clarke L, Carbon J. 1976. A colony bank containing synthetic Col El hybrid plasmids representativeof the entire E. coli genome. Cell 9:91-99.Das L, Martienssen R. 1995. Site-selected transposon mutagenesis at the hfc109 locus in maize.Plant Cell 7:287-294.Dennis ES, Brettell RIS, Peacock WJ. 1987. A tissue culture induced Adh null mutant of maizeresults from a single base change. Mol. Gen. Genet. 210:181-183.Grandbastien M-A. 1998. Activation of plant retrotransposons under stress conditions. TrendsPlant Sci. 3:181-187.Retrotransposons of rice as a tool . . . 289