Identification of the orphan GPCR, P2Y(10) receptor as the sphingosine-1-phosphate and lysophosphatidic acid receptor

Phylogenetic analysis of transmembrane regions of GPCRs using PHYLIP indicated that the orphan receptor P2Y₁₀ receptor was classified into the cluster consisting nucleotide and lipid receptors. Based on the results, we studied the abilities of nucleotides and lipids to activate the P2Y₁₀ receptors. As a result, sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA) evoked intracellular Ca²⁺ increases in the CHO cells stably expressing the P2Y₁₀ fused with a G_16α protein. These Ca²⁺ responses were inhibited by S1P receptor and LPA receptor antagonists. The introduction of siRNA designed for P2Y₁₀ receptor into the P2Y₁₀-CHO cells effectively blocked both S1P- and LPA-induced Ca²⁺ increases. RT-PCR analysis showed that the mouse P2Y₁₀ was expressed in reproductive organs, brain, lung and skeletal muscle, suggesting the receptor plays physiological roles throughout the whole body. In conclusion, the P2Y₁₀ receptor is the first receptor identified as a dual lysophospholipid receptor.     

Genome Structure of the Legume, Lotus japonicus

The legume Lotus japonicus has been widely used as a model system to investigate the genetic background of legume-specific phenomena such as symbiotic nitrogen fixation. Here, we report structural features of the L. japonicus genome. The 315.1-Mb sequences determined in this and previous studies correspond to 67% of the genome (472 Mb), and are likely to cover 91.3% of the gene space. Linkage mapping anchored 130-Mb sequences onto the six linkage groups. A total of 10 951 complete and 19 848 partial structures of protein-encoding genes were assigned to the genome. Comparative analysis of these genes revealed the expansion of several functional domains and gene families that are characteristic of L. japonicus. Synteny analysis detected traces of whole-genome duplication and the presence of synteny blocks with other plant genomes to various degrees. This study provides the first opportunity to look into the complex and unique genetic system of legumes.Key words: Lotus japonicus, genome structure, Fabaceae, comparative analysis     

A High-density Linkage Map of Lotus japonicus Based on AFLP and SSR Markers

A collection of 94 F₆ individuals derived from crosses between Lotus japonicus, Gifu B-129 (G) and Miyakojima MG-20 (M) were used for mapping. By using the HEGS running system, 427 EcoRI/MseI primer pairs were selected to generate a total of 2053 markers, consisting of 739 G-associated dominant markers, 674 M-associated dominant markers, 640 co-dominant markers, 95 SSR markers and 2 dCAPS markers. Excluding heavily distorted markers, 1588 were mapped to six chromosomes of the L. japonicus genome based on the 97 reference markers. This linkage map consisted of 1023 unique markers (excluding duplicated markers) and covered a total of 508.5 cM of the genome with an average chromosome length of 84.7 cM and interval distance of 0.50 cM. Fifteen quantitative traits loci for eight morphological traits were also mapped. This linkage map will provide a useful framework for physical map construction in L. japonicus in the near future.Key words: Lotus japonicus, AFLP, SSR, linkage map, HEGS (high efficiency genome scanning)     

Formation of acetyltropine in Datura callus cultures

The production of tropoylesters in suspension cultures of Datura innoxia stem callus was significantly stimulated by dl-tropic acid, phenylpyruvate or tropine, but was little affected by l-phenylalanine or l-ornithine. Analyses have shown that acetyltropine is synthesized in large quantities by cultured cells when tropine has been supplied to various cultures of D. innoxia and D. tatula. Acetyltropine has been isolated from either the culture medium or cells supplied with tropine. These results indicate that tropine absorbed by the cultured cells of Datura is esterified predominantly by acetic acid to form acetyltropine, instead of other tropane alkaloids.     

Patterns of selection and allele diversity of class I and class II major histocompatibility loci across the species range of sockeye salmon (Oncorhynchus nerka)

The major histocompatibility complex (MHC), an important component of the vertebrate immune system, provides an important suite of genes to examine the role of genetic diversity at non‐neutral loci for population persistence. We contrasted patterns of diversity at the two classical MHC loci in sockeye salmon (Oncorhynchus nerka), MHC class I (UBA) and MHC class II (DAB), and neutral microsatellite loci across 70 populations spanning the species range from Washington State to Japan. There was no correlation in allelic richness or heterozygosity between MHC loci or between MHC loci and microsatellites. The two unlinked MHC loci may be responding to different selective pressures; the distribution of F_ST values for the two loci was uncorrelated, and evidence for both balancing and directional selection on alleles and lineages of DAB and UBA was observed in populations throughout the species range but rarely on both loci within a population. These results suggest that fluctuating selection has resulted in the divergence of MHC loci in contemporary populations.