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Use of RFLPs larger than 100 kbp to map the position and internal organization of the nucleolus organizer region on chromosome 2 in Arabidopsis thaliana
Author(s) -
Copenhaver Gregory P.,
Doelling Jed H.,
Gens J. Scott,
Pikaard Craig S.
Publication year - 1995
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1995.7020273.x
Subject(s) - biology , genetics , restriction fragment length polymorphism , locus (genetics) , ribosomal rna , gene , nucleolus , nucleolus organizer region , microbiology and biotechnology , chromosome , polymerase chain reaction , cytoplasm
Summary In Arabidopsis thaliana ribosomal RNA genes (rRNA genes or rDNA) are grouped in two nucleolus organizer regions (NORs) that together comprise approximately 6% of the genome. The map positions of the NORs relative to other genetic markers are unknown. It was found that the restriction endonuclease Hin dIII cuts once in some but not all rRNA genes to yield strain‐specific RFLPs of 100–700 kb that could be visualized by pulsed‐field gel electrophoresis and Southern blotting. The Hin dIII RFLPs of the A. thaliana strains Columbia and Landsberg segregated among recombinant inbred lines derived from a cross between these two strains. Linkage analysis placed the NOR bearing the polymorphic Hin dIII sites to the top of the upper arm of chromosome 2. The name NOR2 is suggested for this locus. Hin dIII‐bearing rRNA genes are interspersed with clusters of Hin dIII‐less genes throughout NOR2 . The observed clustering is most consistent with unequal crossing‐over, or nearest‐neighbor gene conversion, as the mechanism(s) that spread rRNA gene variants throughout an NOR. No meiotic cross‐over events yielding a ‘hybrid’ NOR with multiple RFLPs from both parents were observed among the 47 recombinant inbred lines examined. However, the appearance of novel Hin dIII profiles in approximately 40% of the recombinant inbred lines demonstrates that fluctuations in the distribution of rRNA gene variants occur frequently and can be readily detected on pulsed‐field gels.