Plant & Animal Genome VI Conference

W71

CONSEQUENCES OF POLYPLOID FORMATION FOR THE STRUCTURE AND FUNCTION OF THE COTTON GENOME

Department of Soil and Crop Science, Texas A&M University, College Station, TX 77843-2474

While it has long been recognized that polyploidy resulted in extensive gene duplication and co-linear gene order along homoeologous cotton chromosomes, these predictable features are accompanied by a host of surprising consequences of polyploidy. Consistent with their cytologically-large chromosomes and relatively high C-value, A-genome diploid cottons contain a large number of dispersed repetitive DNA families that are rare or absent from D-genome diploid cottons. Subsequent to A-D polyploid formation, these repetitive DNA elements have followed a remarkable diversity of evolutionary paths, but with a general tendency toward homogenization of the two subgenomes - in striking contrast to the strict bivalent and homologous pairing of the cotton chromosomes. Regarding the genetic control of agriculturally-important traits, striking biases in the subgenomic distribution (A versus D) of genes and QTLs support evolutionary models which suggest that polyploid formation creates the opportunity for "novel avenues of response to selection." Further dissection of the molecular-level consequences of polyploidy is an important dimension of comparative genetic analysis, with many ramifications for agricultural productivity, and for streamlining genomics research.