Molecular cloning and characterization of iojap (ij), a pattern striping gene of maize.

Abstract

Iojap (ij) is a recessive striped mutant of maize affecting the development of plastids in a local and position‐dependent manner on the leaves. The ij‐affected plastids are transmitted to some of the progeny even when the function of the nuclear gene is restored. Developmental defects during embryogenesis and leaf proliferation are other phenotypic characteristics of ij. The extent of striping and the degree of developmental arrest in ij depend upon genetic background. To understand the diverse and unique phenotypic expression of ij, a transposon tagging experiment has been conducted using Robertson's Mutator (Mu). A new ij mutant was obtained from crosses of the reference allele of (ij‐ref) to Mu lines. Subsequent genetic and molecular studies showed that the mutant carried a new ij allele (ij‐mum1) from the Mu lines and contained a Mu1 element that cosegregated with the iojap phenotype. A 6.0 kb EcoRI genomic DNA fragment containing the Mu1 element was cloned. ij‐ref is unstable, and revertants (Ij‐Rev) have been obtained. Using the flanking DNA from the genomic clone as a probe, DNA polymorphisms were detected between ij‐ref and these revertants. Further, transcripts were restored to the normal level in Ij‐Rev seedlings. Comparison of genomic DNA clones from ij‐ref, ij‐mum1 and Ij indicated that the ij‐ref allele contained 1.5 kb of additional DNA related to a transposable element, Ds. Germinal and somatic revertant alleles were derived by excision of this 1.5 kb element from ij‐ref. The structure of the Ij gene and the DNA sequence of its transcribed region were determined. The Ij gene encodes a 24.8 kDa protein that showed no significant sequence similarity with proteins listed in databases.

A Pentatricopeptide Repeat Protein Facilitates the trans-Splicing of the Maize Chloroplast rps12 Pre-mRNA

“…It is labor intensive to assess the expression of each candidate gene in search of the underlying molecular lesion. This problem is exacerbated in albino mutants lacking plastid ribosomes because they exhibit stereotypical defects in chloroplast RNA metabolism (Han et al, 1992(Han et al, , 1995Hess et al, 1993;Jenkins et al, 1997;Williams and Barkan, 2003). These aberrant transcript patterns are caused in part by the loss of the plastidencoded RNA polymerase, as the nuclear-encoded polymerase activity recognizes a distinct set of promoters (Hajdukiewicz et al, 1997).…”

tie-dyed1Functions Non-Cell Autonomously to Control Carbohydrate Accumulation in Maize Leaves

“…ij1 is a recessive mutation that causes defects in chloroplasts in some cells early in development, resulting in longitudinal stripes of albino tissue in an otherwise largely green leaf ( Fig. 3A; Han et al, 1992). Leaves from ij1; tdy1 double mutants show that the tdy1 phenotypic region, marked by anthocyanin pigmentation, is capable of spreading into albino tissue (Fig.…”

Leaf-variegated mutations and their responsible genes in Arabidopsis thaliana.

“…In contrast, there is no evidence yet that a stripe mutation in monocotyledons is caused by a mechanism similar to any of the Arabidopsis cases. A maize mutant iojap (ij) is one of the oldest stripe mutants known in literature, and the responsible gene has been cloned by transposon tagging (Han et al, 1992). The IJ gene encodes a novel chloroplast protein with any known predictable function.…”