Molecular mapping of 2 environmentally sensitive male-sterile mutants in soybean.

In soybean [Glycine max (L.) Merr.], manual cross-pollination to produce large quantities of hybrid seed is difficult and time consuming. Identification of an environmentally stable male-sterility system could make hybrid seed production commercially valuable. In soybean, 2 environmentally sensitive male-sterile, female-fertile mutants (ms8 and msp) have been identified. Inheritance studies showed that sterility in both mutants is inherited as a single gene. The objectives of this study were to 1) confirm that msp and ms8 are independent genes; 2) identify the soybean chromosomes that contain the msp and the ms8 genes using bulked segregant analyses (BSAs); and 3) make a genetic linkage map of the regions containing these genes. Mapping populations consisting of 176 F(2) plants for ms8 and 134 F(2) plants for msp were generated. BSA revealed that Sat_389 and Satt172 are closely associated markers with ms8 and msp, respectively. Map location of Sat_389 suggested that the ms8 gene is located on chromosome 7; molecular linkage group (MLG) M. Map location of Satt172 indicated that the msp gene is located on chromosome 2 (MLG Dlb). Genetic linkage maps developed using F(2) populations revealed that ms8 is flanked by a telomere and Sat_389 and msp is flanked by Sat_069 and GMES4176. The region between the telomere and Sat_389 is physically 160 Kb. Soybean sequence information revealed that there are 13 genes present in that region. Protein BLASTP analyses revealed that homologs of 3 of the 13 genes are known to a play role in cell division, suggesting putative candidates for ms8.

Systemic acquired resistance in soybean is regulated by two proteins, Orthologous to Arabidopsis NPR1.

BACKGROUND: Systemic acquired resistance (SAR) is induced in non-inoculated leaves following infection with certain pathogenic strains. SAR is effective against many pathogens. Salicylic acid (SA) is a signaling molecule of the SAR pathway. The development of SAR is associated with the induction of pathogenesis related (PR) genes. Arabidopsis non-expressor of PR1 (NPR1) is a regulatory gene of the SA signal pathway 123. SAR in soybean was first reported following infection with Colletotrichum trancatum that causes anthracnose disease. We investigated if SAR in soybean is regulated by a pathway, similar to the one characterized in Arabidopsis. RESULTS: Pathogenesis-related gene GmPR1 is induced following treatment of soybean plants with the SAR inducer, 2,6-dichloroisonicotinic acid (INA) or infection with the oomycete pathogen, Phytophthora sojae. In P. sojae-infected plants, SAR was induced against the bacterial pathogen, Pseudomonas syringae pv. glycinea. Soybean GmNPR1-1 and GmNPR1-2 genes showed high identities to Arabidopsis NPR1. They showed similar expression patterns among the organs, studied in this investigation. GmNPR1-1 and GmNPR1-2 are the only soybean homologues of NPR1and are located in homoeologous regions. In GmNPR1-1 and GmNPR1-2 transformed Arabidopsis npr1-1 mutant plants, SAR markers: (i) PR-1 was induced following INA treatment and (ii) BGL2 following infection with Pseudomonas syringae pv. tomato (Pst), and SAR was induced following Pst infection. Of the five cysteine residues, Cys82, Cys150, Cys155, Cys160, and Cys216 involved in oligomer-monomer transition in NPR1, Cys216 in GmNPR1-1 and GmNPR1-2 proteins was substituted to Ser and Leu, respectively. CONCLUSION: Complementation analyses in Arabidopsis npr1-1 mutants revealed that homoeologous GmNPR1-1 and GmNPR1-2 genes are orthologous to Arabidopsis NPR1. Therefore, SAR pathway in soybean is most likely regulated by GmNPR1 genes. Substitution of Cys216 residue, essential for oligomer-monomer transition of Arabidopsis NPR1, with Ser and Leu residues in GmNPR1-1 and GmNPR1-2, respectively, suggested that there may be differences between the regulatory mechanisms of GmNPR1 and Arabidopsis NPR proteins.