Genes & Genetic Systems
Online ISSN : 1880-5779
Print ISSN : 1341-7568
ISSN-L : 1341-7568
Volume 85, Issue 2
Displaying 1-7 of 7 articles from this issue
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  • Sachiyo Isokawa, Masaaki Osaka, Akira Shirasawa, Rina Kikuta, Satoshi ...
    2010 Volume 85 Issue 2 Pages 87-96
    Published: 2010
    Released on J-STAGE: June 15, 2010
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    Self-incompatibility (SI) in Brassicaceae is sporophytically controlled by a single S-locus with multi allelic variety. The male S determinant, SP11/SCR (S-locus protein 11/S-locus cysteine-rich protein), is a small cysteine-rich protein, and the female S determinant, SRK (S-locus receptor kinase), functions as a receptor for SP11 at the surface of stigma papilla cells. Although a few of the following downstream factors in the SP11-SRK signaling cascade have been identified, a comprehensive understanding of the SI mechanism still remains unexplained in Brassicaceae. Analysis of self-compatible (SC) mutants is significant for understanding the molecular mechanism in SI reactions, thus we screened SC lines from a variety of Japanese bulk-populations of B. rapa vegetables. Two lines, TSC4 and TSC28, seem to have disruptions in the SI signaling cascade, while the other line, TSC2, seems to have a deficiency in a female S determinant, SRK. In TSC4 and TSC28, known SI-related factors, i.e. SRK, SP11, MLPK (M-locus protein kinase), THL (thioredoxin-h-like), and ARC1 (arm repeat containing 1), were expressed normally, and their expression levels were comparable with those in SI lines. On a B. rapa genetic linkage map, potential SC genes in TSC4 and TSC28 were mapped on linkage groups A3 and A1, respectively, whereas MLPK, ARC1, and THL were mapped on A3, A4, and A6, respectively. Although potential SC genes of TSC4 and MLPK were on the same linkage group, their positions were apparently independent. These results indicate that the SC genes of TSC4 and TSC28 are independent from the S-locus or known SI-related genes. Thus, the SC lines selected here have mutations in novel factors of the SI signaling cascade, and they will contribute to fill pieces in a signal transduction pathway of the SI system in Brassicaceae.
  • Min Jeong Hong, Dae Yeon Kim, Tong Geon Lee, Woong Bae Jeon, Yong Weon ...
    2010 Volume 85 Issue 2 Pages 97-106
    Published: 2010
    Released on J-STAGE: June 15, 2010
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    Pectin, one of the main components of plant cell wall, is deesterified by the pectin methylesterase (PME). PME activity is regulated by inhibitor proteins known as the pectin methylesterase inhibitor (PMEI), which plays a key role in wounding, osmotic stress, senescence and seed development. However, the role of PMEI in many plant species still remains to be elucidated, especially in wheat. To facilitate the expression analysis of the TaPMEI gene, RT-PCR was performed using leaf, stem and root tissues that were treated with exogeneous application of phytohormones and abiotic stresses. High transcription was detected in salicylic acid (SA) and hydrogen peroxide treatments. To elucidate the subcellular localization of the TaPMEI protein, the TaPMEI:GFP fusion construct was transformed into onion epidermal cells by particle bombardment. The fluorescence signal was exclusively detected in the cell wall. Using an enzyme assay, we confirmed that PME was completely inhibited by TaPMEI. These results indicated that TaPMEI was involved in inhibition of pectin methylesterification and may play a role in the plant defense mechanism via cell wall fortification.
  • Susumu Oda, Fumi Kaneko, Kentaro Yano, Tomoaki Fujioka, Hiromi Masuko, ...
    2010 Volume 85 Issue 2 Pages 107-120
    Published: 2010
    Released on J-STAGE: June 15, 2010
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    Supplementary material
    Cool temperature conditions are known to lead to pollen sterility in rice. Pollen sterility is an agriculturally important phenomenon because it imparts a large influence directly on rice yield. However, cool temperature stress tolerance varies among rice cultivars and avoidance of cool temperature stress is difficult by practical method of agriculture. In this study using two rice cultivars, Hitomebore (high tolerance) and Sasanishiki (low tolerance), we analyzed morphological features and gene expression profiles, under cool temperature stress, in anther development of rice. Hitomebore was given cool temperature stress (19°C) at flowering stage, and showed 87.3% seed fertility. Meanwhile, the seed fertility decreased to 41.7% in the case of Sasanishiki. A transverse section of Hitomebore anther revealed that the degradation of the tapetum started at the uninucleate microspore stage, and the tapetum had completely vanished at mature stage. The tapetum provides nutrients for pollen development, and its degradation occurs at a late stage in pollen development. In contrast, degradation of the tapetum did not occur at the uninucleate microspore stage in Sasanishiki, and the tapetum was clearly intact at mature stage, suggesting that tapetum degradation is critical for accurate pollen development and cool temperature tolerance correlated with the degree of tapetum degeneration. In gene expression analysis of anther, 356 genes that showed different expression levels between two cultivars at cool temperatures were found. These genes will lead to understanding the mechanism of cool temperature stress response in rice pollen development and the identification of genes involved in accurate tapetum degradation.
  • Takashi Kitano, Masahiro Satou, Naruya Saitou
    2010 Volume 85 Issue 2 Pages 121-127
    Published: 2010
    Released on J-STAGE: June 15, 2010
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    We determined cDNAs of two genes that belong to the Rhesus (Rh) blood group gene family in an amphioxus species (Branchiostoma floridae) and designated them Rh-related-1 (RhR-1) and Rh-related-2 (RhR-2). RhR-1 and RhR-2 consisted of 10 and 11 exons, respectively. 3’ UTR sequences of RhR-1 were shorter (220–272 bp) than those of RhR-2 (1,505–1,650 bp). CDS lengths were 1,344 and 1,476 bp for RhR-1 and RhR-2, respectively, and the average nucleotide difference between their CDS regions was 0.33. The corresponding regions of Rh genes from exons 2 to 7 were relatively conserved among the chordate species examined in this study. Length difference numbers were in multiples of three, which implies that codon frames were conserved among them, and the same exon/intron boundary phases were observed in those regions. This region was used for the phylogenetic analyses. RhR-1 and RhR-2 formed a cluster on the phylogenetic tree of the Rh gene family. Gene duplication time of RhR-1 and RhR-2 was estimated to be ca. 500 million years ago. It is likely that the four Rh family genes in vertebrates emerged by gene duplications in the common ancestor of vertebrates, and functional differentiation has occurred after the first gene duplication.
  • Masaki Eda, Masaki Kuro-o, Hiroyoshi Higuchi, Hiroshi Hasegawa, Hiroko ...
    2010 Volume 85 Issue 2 Pages 129-139
    Published: 2010
    Released on J-STAGE: June 15, 2010
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    Supplementary material
    Although the tandem duplication of mitochondrial (mt) sequences, especially those of the control region (CR), has been detected in metazoan species, few studies have focused on the features of the duplicated sequence itself, such as the gene conversion rate, distribution patterns of the variation, and relative rates of evolution between the copies. To investigate the features of duplicated mt sequences, we partially sequenced the mt genome of 16 Phoebastria albatrosses belonging to three species (P. albatrus, P. nigripes, and P. immutabilis). More than 2,300 base pairs of tandemly-duplicated sequence were shared by all three species. The observed gene arrangement was shared in the three Phoebastria albatrosses and suggests that the duplication event occurred in the common ancestor of the three species. Most of the copies in each individual were identical or nearly identical, and were maintained through frequent gene conversions. By contrast, portions of CR domains I and III had different phylogenetic signals, suggesting that gene conversion had not occurred in those sections after the speciation of the three species. Several lines of data, including the heterogeneity of the rate of molecular evolution, nucleotide differences, and putative secondary structures, suggests that the two sequences in CR domain I are maintained through selection; however, additional studies into the mechanisms of gene conversion and mtDNA synthesis are required to confirm this hypothesis.
  • Ibrahim A. Arif, Haseeb A. Khan, Mohammad Shobrak, Ali A. Al Homaidan, ...
    2010 Volume 85 Issue 2 Pages 141-145
    Published: 2010
    Released on J-STAGE: June 15, 2010
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    Arabian oryx (Oryx leucoryx) is an endangered antelope that is being protected by captive breeding programs. However, the long term success of these programs mainly depends on the prudent use of molecular information for conservation management. We have used an array of seven microsatellite loci to examine the molecular diversity in a representative population of 24 captive-bred and reintroduced Arabian oryx. The locus-wise mean observed heterozygosity (0.601) was found to be comparatively higher than the mean expected heterozygosity (0.565). The specimen-wise observed heterozygosity ranged from 0.143 to 1.00 with an average of 0.60 whereas the mean d2 varied from 0.57 to 1023.428 with an average value of 223.357. The results of Shannon information index (I = 0.898) also indicated a high level of within population genetic diversity. The average gene flow was 0.298, ranging between 0.204 and 0.424 for different loci. In conclusion, the information about the extent of heterozygosity, allelic diversity and inbreeding/outbreeding depression using microsatellite markers could be of potential relevance for the management of captive breeding programs for the conservation of Arabian oryx.
  • Yoshiki Yasukochi, Toshifumi Kurosaki, Masaaki Yoneda, Hiroko Koike
    2010 Volume 85 Issue 2 Pages 147-155
    Published: 2010
    Released on J-STAGE: June 15, 2010
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    Genetic diversity estimation of the major histocompatibility complex (MHC) gene may be an important tool in the assessment of immune response ability against infectious disease. We were able to identify a near full-length expressed DQB sequence by RACE-PCR method from the Asiatic black bear, Ursus thibetanus in Japan. This is the first such full length expression in the Ursidae. The bear had at least one functional DQB locus. In phylogenetic tree analysis its DQB amino acid sequence formed a monophyletic group with DQB sequences from members of the order Carnivora and had a 90% nucleotide sequence similarity with the DQB allele of the California sea lion, Zalophus californianus. We compared the DQB amino acid composition of U. thibetanus with those of several other mammalian species including Homo sapiens. Amino acid residues known to be functionally important for human MHC genes, tended to be also conserved among other mammalian species while PBRs in the β1 domain were heterogeneous among mammalian species. The DQB sequence obtained from the bear had not only no putative frameshifts or deletions but also no abnormal amino acid mutations such as had been observed in human DQB molecules. This suggests that the bear DQB sequence was an apparently functional DQB allele. As a preliminary study, we sequenced the exon 2 region of DQB alleles from genomic DNA, and succeeded to amplify the exon 2 of DQB loci. Our study will provide useful information for conservation genetics of the U. thibetanus as well as more generally regarding the mammalian MHC region.
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