Gene expression of soybean roots inoculated with wild-type and type III secretion mutant strains of Bradyrhizobium elkanii. Glycine max

To dissect differences in gene expression profile of soybean roots inoculated with wild-type and type III secretion mutant rhizobia, we have employed microarray analysis. Seeds of soybeans (Glycine max L. cv. Enrei and its non-nodulating line En1282) were surface-sterilized and germinated at 25 °C for 2 days and were transferred to a plant box (CUL-JAR300; Iwaki, Tokyo, Japan) containing sterile vermiculite watered with B&D nitrogen-free medium (Broughton and Dilworth 1971). One day after transplant, each seedling was inoculated with Bradyrhizobium elkanii USDA61, its type III secretion mutant BerhcJ or sterilized water (mock treatment). Plants were cultivated in a growth chamber at 25°C and 70% humidity with a daytime of 16 h followed by a nighttime of 8 h. To determine the gene expression, RNA was extracted from the roots 8 days after inoculation. Overall design: Gene expression in soybean roots inoculated with Bradyrhizobium elkanii USDA61, its type III secretion mutant BerhcJ or sterilized water (mock treatment) was measured 8 days after inoculation. Three independent experiments were performed at each inoculation.