Plant & Animal Genome IX Conference

Poster: Large Insert Libraries, Gene Isolation, Etc.
P02_30.html

GENE EXPRESSION ANALYSES OF A RESISTANCE GENE CLUSTER ON SOYBEAN LINKAGE GROUP J

¹ Agronomy Department, Iowa State University, Ames, IA 50011-1010

² USDA-ARS, Corn Insect and Crop Genetics Research Unit, Agronomy Department, Iowa State University, Ames, IA 50011-1010

In soybean, PCR amplification has been used to identify a cluster of RGAs on soybean linkage group J. Resistance to powdery mildew (Rmd-c), Phytophthora stem and root rot (Rps2) and an ineffective nodulation gene (Rj2) map within this cluster. Using RGA-specific primers and BAC fingerprinting, a contig of BACs was developed for this region in cultivar 'Williams 82' (rps2, Rmd (adult onset), rj2; Marek and Shoemaker, 1997). Two cDNAs showing homology to RGAs have also been placed in the contig. Because the two cDNAs were derived from different tissues, we became interested in determining if differential expression of the R-genes occurs within this cluster. Several different techniques were employed to obtain sequence information from twelve different R-genes within a single 120 kb BAC. Sequence differences between the genes were used to design gene-specific primers for the twelve genes. The primers are being used to examine the expression of the genes by RT-PCR in different tissues and at different stages of development. We have also constructed two additional BAC contigs for this region from soybean cultivars L76-1988 (Rps2, Rmd-c, Rj2) and L82-2024 (rps2, rmd, rj2). Using the primers developed from the Williams 82 R-genes, we hope to examine the expression of R-genes from L76-1988 and L82-2024 under different conditions, including post-pathogen inoculation.