Oregon State University
Plant Gene Expression Center

The maize shootless mutation dks8 does not map to known Knotted-like genes or shootless dek loci
--Hardeman, K; Chuck, G; Hake, S and Rivin, CJ

The shootless mutation dks8 (defective kernel shootless Mu8) leads to small seeds that contain an embryo with a functional root meristem and normal appearing cotyledon, but no observable shoot components. Previously, dks8 was found to cosegregate with a Mu8-hybridizing fragment in 70 individuals (Sollinger and Rivin, MNL 67: 34-35, 1993). As we have only one allele of dks8, we were interested in determining its map position to allow us to determine if any previously isolated defective kernel mutation mapped to a similar location. In addition, we were interested in whether any of the Knotted-like genes in maize mapped to the dks8 location, as a shootless mutation in Arabidopsis has been shown to be mutated in an Arabidopsis Kn1-like gene (J. Medford and K. Barton, pers. comm).

The Mu8-hybridizing fragment that is tightly linked to dks8 was cloned and the flanking region was assigned the map location 2S-36 using the recombinant inbred (RI) family Tx303 x CO159. Therefore, the dks8 mutation resides on chromosome arm 2S. Two defective kernel mutations have previously been mapped to chromosome arm 2S, et2 and dek3. Allelism tests revealed that dks8 is not allelic to et2. Allelism tests with dek3 are in progress. No known Knotted-like genes map to this area of 2S.

The Mu8 flanking sequence appears to represent a gene with two copies in the genome, as it was found to hybridize less strongly to an additional fragment. This other locus was also mapped using the RI family Tx303 x Co159 and it maps to position 10L-116. 

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