Maize Genetics Cooperation Newsletter 80. 2006.

The mutations sh2-i and sh2-N2340 share an identical intron splice site mutation and are most likely the same allele

--Clancy, M; Hannah, LC

The mutant alleles sh2-i and sh2-N2340 were generated by Dr. M. G. Neuffer using EMS mutagenesis. The mutation sh2-N2340 is available from the Maize Stock Center. These two mutants condition an intermediate or leaky phenotype. Mature kernels are less severely collapsed compared to the reference allele sh2-R. Sequencing established that sh2-i contains a G to A transition at the 3� terminus of intron 2 (Lal et al., Plant Physiol. 120:65-72, 1999). Approximately 10% of sh2-i transcripts are correctly spliced utilizing the mutant intron splice site. This generates a low level of adenosine diphosphate glucose pyrophosphorylase activity that results in the intermediate kernel phenotype.

Because sh2-i and sh2-N2340 kernels are visually so similar and trace to the same source, we asked whether they contain the same mutation. Young shoot material was harvested from germinating sh2-N2340 kernels, and genomic DNA was prepared using Plant DNAZOL Reagent (Invitrogen). DNA spanning exons 1 through 4 was amplified via PCR using the primers described by Lal et al. (1999). Sequencing of the PCR product established that sh2-i and sh2-N2340 share the same G to A transition of the final nucleotide in intron 2. Hence, it appears most likely that the same mutation bears two different designations.

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