ANALYSIS OF MUTATOR-INDUCED MUTATIONS IN THE IOJAP GENE OF MAIZE

The recessive nuclear mutation iojap (ij) in maize produces striped pl ants with normal chloroplasts in green sectors and poorly developed ch loroplasts in the white sectors. The ij mutation is also characterized by an array of additional phenotypic affects which suggests a pivotal role for Ij in chloroplast development. The Ij gene from maize has be en isolated; however, the sequence has not provided information on the action of the Ij gene product. As an extension of the analysis of the Ij gene we have generated a number of independent transposon insertio n mutations using the Robertson's Mutator (Mu). Insertions were found to be distributed throughout the 5' half of the gene and all showed a similar striping pattern to that of the original ij mutation, ij-ref. While several of the new mutant alleles produced ij-homologous transcr ipts none produced detectable levels of the Ij polypeptide product. Ch loroplast development in some cells appears to be able to proceed in t he absence of the Ij polypeptide.