RAV is a unique transcription factor in higher plants with AP2 and B3-like two distinct DNA-binding domains, but its roles in plant growth and development remains unknown. We have isolated a novel RAV family gene from Galegae orientalis, called GoRAV, which responds to cold induction. Sequence alignment showed that it shares high identity with other RAV family members in AP2 and B3 domain. Transient expression analysis using onion epidermal cells indicated that GoRAV protein is localized in the nucleus. Semi-quantitative RT-PCR (S-Q RT-PCR) analysis indicated that GoRAV is induced by cold, dehydration, high-salinity and abscisic acid, with the strongest induction in G. orientalis leaves during the early response to abiotic elicitors. GoRAV is more abundant in leaf than in stem, but is not expressed in root. This work adds a new member to the RAV family.

View full abstract

Salinity severely affects plant growth and development causing crop loss worldwide. We have isolated a large number of salt-induced genes as well as unknown and hypothetical genes from Salicornia brachiata Roxb. (Amaranthaceae). This is the first description of identification of genes in response to salinity stress in this extreme halophyte plant. Salicornia accumulates salt in its pith and survives even at 2 M NaCl under field conditions. For isolating salt responsive genes, cDNA subtractive hybridization was performed between control and 500 mM NaCl treated plants. Out of the 1200 recombinant clones, 930 sequences were submitted to the NCBI database (GenBank accession: EB484528 to EB485289 and EC906125 to EC906292). 789 ESTs showed matching with different genes in NCBI database. 4.8% ESTs belonged to stress-tolerant gene category and approximately 29% ESTs showed no homology with known functional gene sequences, thus classified as unknown or hypothetical. The detection of a large number of ESTs with unknown putative function in this species makes it an interesting contribution. The 90 unknown and hypothetical genes were selected to study their differential regulation by reverse Northern analysis for identifying their role in salinity tolerance. Interestingly, both up and down regulation at 500 mM NaCl were observed (21 and 10 genes, respectively). Northern analysis of two important salt tolerant genes, ASR1 (Abscisic acid stress ripening gene) and plasma membrane H⁺ATPase, showed the basal level of transcripts in control condition and an increase with NaCl treatment. ASR1 gene is made full length using 5’ RACE and its potential role in imparting salt tolerance is being studied.

View full abstract

Intra-and interspecific DNA variations in the blast resistance gene Pita in wild rice (Oryza rufipogon), cultivated rice (O. sativa), and two other related wild rice species (O. meridionalis and O. officinalis) were analyzed to elucidate the nucleotide polymorphism maintenance mechanisms and evolution of Pita in these species. Nucleotide diversity at silent sites of O. rufipogon Pita was 0.0101, an intermediate value relative to other O. rufipogon nuclear genes. A dimorphic pattern of nucleotide polymorphism was detected in the O. rufipogon Pita region. Inoculation of the blast fungus Magnaporthe oryzae verified that the O. rufipogon Pita gene resides in a dimorphic sequence type. The resistance Pita allele had lower levels of variation than the susceptibility pita allele. A hypothesis of evolutionary relationships indicated that the amino acid mutation in the O. rufipogon Pita protein responsible for the difference between resistance and susceptibility occurred relatively recently. These results suggested that the resistance Pita originated from the susceptibility pita. Nucleotide diversity at replacement sites of the leucine-rich domain (LRD) of both the resistance and susceptibility O. rufipogon pita was low. In tests of neutrality, significantly negative values were detected for the LRD of O. rufipogon susceptibility pita. The low nucleotide diversity at replacement sites of the LRD of the susceptibility pita could be explained by purifying selection. Comparison of Pita between O. rufipogon and O. officinalis revealed an excess of nonconservative amino acid substitutions in the LRD, which could be related to the host-pathogen interaction.

View full abstract

The DROOPING LEAF (DL) gene regulates carpel specification in the flower and midrib formation in the leaf in Oryza sativa (rice). Loss-of-function mutations in the dl locus cause homeotic transformation of carpels into stamens and lack of midrib, resulting in the drooping leaf phenotype. DL is a member of the YABBY gene family and is closely related to the CRABS CLAW (CRC) gene in Arabidopsis thaliana. The function of Arabidopsis CRC, however, differs from that of rice DL: it is responsible for nectary development and is partially involved in carpel identity. Thus, genes related to DL/CRC seem to have functionally diversified during angiosperm evolution. To assess the conservation of DL function in related species, here we examined the in situ expression patterns of DL orthologs in three grass species, i.e., maize, wheat and sorghum, which is assigned to subfamilies different from Ehrhartoideae including O. sativa. The results clearly show that the temporal and spatial expression patterns of DL orthologs in the three species are identical to those of rice DL in both flower and leaf development, suggesting that DL-related genes are functionally conserved within the grass family. It is likely that DL may have been recruited to carpel specification and midrib formation within the lineage of the grass family after divergence of their ancestor from that of eudicots.

View full abstract

During the maintenance of the wild silkworm, Bombyx mandarina, a mutant phenotype exhibiting translucent skin was identified. Based on the crossing experiments with the domesticated silkworm, Bombyx mori, we found that the mutant was controlled by molybdenum cofactor sulfurase (MoCoS) gene. We designated the mutant ‘‘Ozaki’s translucent’’ (og^Z). We found a 2.1-kb deletion containing the transcription initiation site, exons 1 and 2, and the 5' end of exon 3 of the MoCoS gene. The transcript of the MoCoS gene was not detected in the og^Z homozygote. We concluded that og^Z is a complete loss-of-function allele generated by a disruption of the MoCoS gene.

View full abstract

Sparid fishes consist of approximately 115 species in 33 genera that are broadly distributed in tropical and temperate coastal waters. Although several phylogenetic analyses were conducted based on specific molecular markers, their classification remains unresolved. Here, we present the most comprehensive molecular phylogeny of the family Sparidae to date, based on cytochrome b (cyt-b) genes. We determined 18 sequences of sparids and conducted phylogenetic analyses among 72 individuals representing 66 sparids with 23 outgroup species. Phylogenetic trees were constructed according to partitioned Maximum Likelihood (ML) and Bayesian methods. The phylogenetic analyses were conducted on two different data sets (including all positions; RY-coding). The phylogenetic trees showed monophyly of the family Sparidae with a different taxon, centracanthid Spicara. The subfamilies in the Sparidae in all trees are non-monophyletic and do not agree with current classification of the subfamilies. The genera Acanthopagrus, Cheimerius, Dentex, Diplodus, Pagellus, Pagrus, and Spicara are also non-monophyletic and their classifications should be revised based on the phylogenetic relationships and reinvestigation of morphological characters. The sparids are divided into three major clades, A, B and C, respectively in the ML tree based on all codon positions, whereas clade C was paraphyletic in the other trees. The species in clade C are known to be present in the eastern Pacific to western Atlantic, whereas those in clades A and B are distributed in various oceanic regions. Some sub-clades in clades A and B consist of species that are distributed in defined local regions. We further investigated evolutionary patterns of 87 morphological characters by ancestral character-state reconstruction according to the parsimony criteria. The results suggested high evolutionary plasticity of the characters in sparids, indicating that it causes species-diversity and taxonomic confusion at various taxonomic levels, and that such convergent evolution may occur more frequently also in other coastal fishes.

View full abstract

WRN interacting protein 1 (WRNIP1) was originally identified as a protein that interacts with the Werner syndrome responsible gene product (WRN). WRNIP1 is a highly conserved protein from E. coli to humans. Genetic studies in budding yeast suggested that the yeast orthlog of WRNIP1, Mgs1, may function in a DNA damage tolerance pathway that is similar to, but distinct from, the template-switch damage avoidance pathway involving Rad6, Rad18, Rad5, Mms2, and Ubc13. Here we report that human WRNIP1 binds in an ATP dependent manner to both forked DNA that mimics stalled replication forks and to template/primer DNA. We found that WRNIP1 interacts physically with RAD18 and interferes with the binding of RAD18 to forked DNA and to template/primer DNA. In contrast, RAD18 enhances the binding of WRNIP1 to these DNAs, suggesting that WRNIP1 targets DNA bound by RAD18.

View full abstract

A short exposure to light during relative night (night break; NB) delays flowering in the short day plant rice. NB acts by downregulating Heading date 3a (Hd3a) expression. Because phytochrome B mutants do not respond to NB and their flowering time is not affected even under NB conditions, phyB is required for the suppression of Hd3a expression. The effect of NB is quantitatively controlled by light quality and by either light intensity or duration. However, the molecular mechanisms that regulate these interactions are poorly understood. Here, we examine the roles of phytochromes in the regulation of Hd3a transcription under NB conditions using monochromatic red, far-red and blue light. Red and blue light downregulated Hd3a expression, but far-red light NB did not. The effect of red light NB on Hd3a is dependent on photon fluence and is restored by subsequent far-red light irradiation. Our results suggest that quantitative effect of light on flowering in rice NB is mediated by the regulation of Hd3a transcription by phyB.

View full abstract

We report here that a novel 1,869 bp repetitive sequence identified from the false killer whale (Pseudorca crassidens) could be a new molecular phylogenetic marker in cetaceans. Results of PCR amplification and southern blot hybridization using 16 species’ genomic DNAs from five different families revealed that the repetitive sequence is highly conserved within all Delphinidae species. Notably, specific primers designed for this repetitive sequence effectively amplified the targeted repetitive units, which were critically dependent upon the genetic phylogenies in the members of the Delphinidae cetaceans. Therefore, the novel sequences can be used as a useful phylogenetic marker for understanding the molecular evolutional studies in members of the Delphinidae family of cetaceans.

View full abstract