Legume and rhizobia symbiosis plays an important role in conversion of atmospheric dinitrogen to ammonia. On a global scale, thin interaction represent a key entry point for reduced nitrogen into the biosphere, and as a consequence this symbiosis in important in both natural and agricultural systems. Symbiotic development of nodule organ in triggered by chito-oligosaccharide signals(Nod factors) from the bacterium which are perceived by the legume root. Understanding the molecular and cellular processes that underlie Nod factor perception is one focus of legume biology. Although forward genetics has proved to be an important tool to elucidate key players in Nod factor perception, we still know relatively little regarding the functional networks of genes and proteins that connect the earliest steps of Nod factor perception to immediate downstream outcomes. To identify genes and proteins that link Nod factor perception to cellular and physiological responses we are taking a discovery-based strategy on large-scale transcriptome profiling using RNA sequencing in the roots of Medicago truncatula in response to Sinorhizobium meliloti. Functional characterization of a number of candidate genes is currently in progress to further examine their role in nodulation.

Radish, Raphanus sativus L., is an annual vegetable of the family Cruciferae. Radish has RR genome with 18 somatic chromosome numbers (2n=2x=18). Until now, detailed karyotypic analysis is not only constructed only by conventional staining techniques but also other method. Fluorescence in situ hybridization (FISH) is a powerful molecular cytogenetic technique using chromosomal markers that reveal the positions of specific genes, such as ribosomal DNAs, thereby making it easy to identify individual chromosomes. We have constructed detailed karyotypes of four different local and wild varieties of radish, based on the chromosome arm length and fluorescence in situ hybridization (FISH) with the 45S rDNA and 5S rDNA as probes. As for the karyotype of radish, 9 pairs of chromosomes were extremely small in size with about 1 to 3 um in length at mitotic metaphase having metacentrics or submetacentrics. Three pairs of 45S rDNA signals and two pairs of 5S rDNA signals were observed in four radish species. One pair of 45S rDNA signal was located on terminal region of short arm chromosome, while two pairs were in interstitial region. Two pairs of 5S rDNA signals were located on interstitial region of chromosome. In conclusion, it was feasible to identify the radish by karyotype and physical mapping analyzed using ribosomal DNA.