Comparative Genomics of the Genomic Region Controlling Resistance to Puccinia Polysora Underw. in Zea Mays L.

Abstract

Polysora rust (Southern Corn Rust) is a major
disease of maize in tropical and subtropical region
causing yield loss in excess of 45%. The loci governing
resistance (Rpp9, RppQ and RppD) have been mapped to
10.01 bins on short arm of maize chromosome 10, which
also has genes for common rust resistance like Rp1 and
Rp5. With the publication of maize draft genomic
sequence we tried to annotate the region spanning these
genes using comparative genomic tools. We constructed a
physical map using the various loci and the
corresponding markers, BAC clones and contigs reported
from the previous researchers and using MaizeGDB. The
sequence for this region was downloaded from
maizesequence.org. The sequence was scanned for coding
regions using GENSCAN and the CDS and peptides
obtained along with the whole sequence (in bits of 1 MB)
was subjected to BLAST analysis in NCBI-nBLAST,
NCBI-pBLAST, COGE-BLAST and MaizeGDB BLAST.
The region when located on a physical map, had all the
loci governing Polysora rust resistance in a overlapping
position and was around 3 MB size. Two loci RppQ and
RppD covered large portion of the 3MB region whereas
Rpp9 was 82769 bp long. The BLAST results indicated
the similarity of the region to many loci responsible for
disease resistance like PR protein, Serine/threonine
kinase protein, rust resistance protein (rp3-1), receptor
kinases and zein cluster. The region shared homology
with rice, sorghum and brachypodium grass and we
found some orthologs having NB-LRR domain. Hence
from this analysis it could be concluded that the region is
responsible for disease resistance and host many other
genes linked with resistance to various diseases.