Plant Gene Expression Center, USDA-ARS
Location of Adh1 and Kn1 on the linkage map
--Julie Mathern and Sarah Hake
We undertook a RFLP mapping study of the long arm of chromosome 1 in order to place Kn1 and Adh1 on the map and to orient them with respect to the centromere. One of the purposes of this study was to characterize the endpoints of a deletion of Kn1.
The material used for segregation analysis was from self-pollinations
of Kn1-N1 Adh1-S Lw/kn Adh1-Fgamma25
lw heterozygotes. Seedlings were green and knotted, or white and
normal, unless there was recombination. Southern blots of DNA from these
individuals were probed with a Kn1 probe (Hake, Vollbrecht, Freeling
in press), an Adh1 probe and the RFLP markers shown in the table.
We were able to place Kn1 and Adh1 on the RFLP map between
UMC107 and BNL7.25. We found 2 recombinants, one green and normal and the
other white and knotted, at the frequency of 1/200. The proximal marker,
UMC 107, segregated with Kn1 and the distal markers segregated with
Adh1 (and lw), demonstrating that Kn1 is proximal
to Adh1. In both cases the Adh1 allele cosegregated with
its linked lw marker, thus we have not yet determined the placement
of Adh1 relative to lw.
|RFLP CLONE||# INDIVIDUALS TESTED||ESTIMATED MAP UNITS FROM Kn1|
|BNL 7.25||38||8 distal|
We recovered a deletion of Kn1 following X-ray mutagenesis that
is not transmissible through the male. The deletion does not include Adh1
or lw (Hake, Vollbrecht, Freeling, in press). Since we have placed
Adh1 and lw distal to Kn1, we know this deletion extends
less than 1 map unit in the distal direction. Recombination to a proximal
marker, Bz2, does not appear to be affected by the deletion. 68
recombinants were found out of 284, giving a distance of 24mu, similar
to the distance on the genetic map of 22mu. Therefore, the deletion is
relatively small. We tried to uncover the deletion by crossing it to the
TB-1La translocation using Adh1 markers to distinguish the progeny.
We could not recover the genotype for the hypoploid/deletion double heterozygote
in healthy kernels. The ear however did contain defective kernels. This
suggests that the deletion is also homozygous lethal to the embryo. We
are curious whether it is the absence of Kn1 or a closely linked
gene that makes it lethal.
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