Evolutionary Relationships in the Drosophila ananassae Species Cluster Based on Introns of Multiple Nuclear Loci

The Drosophila ananassae species cluster includes D. ananassae, D. pallidosa, D. parapallidosa, and the cryptic species “pallidosa-like”, “pallidosa-like Wau” and “papuensis-like” Some of the taxa are sympatric in the South Pacific, Papua New Guinea, and Southeast Asia, and gene flow between different taxa has been suspected for a handful of genes. In the present analysis, we examined DNA sequences of introns in four loci: alpha actinin (Actn) on XL, white (w) on XR, CG7785 on 2L, and zinc ion transmembrane transporter 63C (ZnT63C) on 2R. Phylogenetic trees (neighbor-joining and haplotype network) were inconsistent among these loci. Some haplotypes shared between taxa were found for w, CG7785, and ZnT63C, suggesting recent gene flow. However, no haplotypes were shared, for example, between D. ananassae and D. pallidosa for CG7785, which is close to the proximal breakpoint of In(2L)D. This suggests that taxon-specific inversions prevent gene flow, as predicted by the chromosomal speciation hypothesis

2.Sediments

金沢大学大学院自然科学研究科　環境科学Royal Netherland Institute for Sea research (NIOZ)Editor : Tazaki, Kazue, Cover:Scanning electoron microscopic photograph of Gallionella sp. in biomats of Aso caldera, Kyusyu, Japan. Various shapes of Gallonella sp. are shown (image:Moriichi, Shingo).COE, 金沢大学 水・土壌環境領域シンポジウム「地球環境における微生物の役割」, 日時：2002年12月4日（水）13：00～, 場所：金沢大学理学部3階第一実験

A metabolome genome-wide association study implicates histidine N-pi-methyltransferase as a key enzyme in N-methylhistidine biosynthesis in Arabidopsis thaliana

A genome-wide association study (GWAS), which uses information on single nucleotide polymorphisms (SNPs) from many accessions, has become a powerful approach to gene identification. A metabolome GWAS (mGWAS), which relies on phenotypic information based on metabolite accumulation, can identify genes that contribute to primary and secondary metabolite contents. In this study, we carried out a mGWAS using seed metabolomic data from Arabidopsis thaliana accessions obtained by liquid chromatography–mass spectrometry to identify SNPs highly associated with the contents of metabolites such as glucosinolates. These SNPs were present in genes known to be involved in glucosinolate biosynthesis, thus confirming the effectiveness of our analysis. We subsequently focused on SNPs detected in an unknown methyltransferase gene associated with N-methylhistidine content. Knockout and overexpression of A. thaliana lines of this gene had significantly decreased and increased N-methylhistidine contents, respectively. We confirmed that the overexpressing line exclusively accumulated histidine methylated at the pi position, not at the tau position. Our findings suggest that the identified methyltransferase gene encodes a key enzyme for N-methylhistidine biosynthesis in A. thaliana

Genomic view of heavy-ion-induced deletions associated with distribution of essential genes in Arabidopsis thaliana

Heavy-ion beam, a type of ionizing radiation, has been applied to plant breeding as a powerful mutagen and is a promising tool to induce large deletions and chromosomal rearrangements. The effectiveness of heavy-ion irradiation can be explained by linear energy transfer (LET; keV µm-1). Heavy-ion beams with different LET values induce different types and sizes of mutations. It has been suggested that deletion size increases with increasing LET value, and complex chromosomal rearrangements are induced in higher LET radiations. In this study, we mapped heavy-ion beam-induced deletions detected in Arabidopsis mutants to its genome. We revealed that deletion sizes were similar between different LETs (100 to 290 keV μm-1), that their upper limit was affected by the distribution of essential genes, and that the detected chromosomal rearrangements avoid disrupting the essential genes. We also focused on tandemly arrayed genes (TAGs), where two or more homologous genes are adjacent to one another in the genome. Our results suggested that 100 keV µm-1 of LET is enough to disrupt TAGs and that the distribution of essential genes strongly affects the heritability of mutations overlapping them. Our results provide a genomic view of large deletion inductions in the Arabidopsis genome

Kinetic studies on free radical reactions : I. Reaction of DPPH with free radicals formed by the photolysis of azo-bis-isobutyronitrile

The formation of free radicals produced by the photo-dissociation of azo-bis-isobutyronitrile (AIBN) in a benzene solution was investigated by the ultra-violet spectrophotometric and ESR methods using DPPH as radical scavenger. From the change of the ultra-violet and ESR spectra of DPPH in the course of irradiation, it was found that the influence of dissolved oxygen on the free radical reaction of AIBN is significant. The peroxy free radicals formed by the reaction of free radicals with dissolved oxygen react with DPPH. The intermediate found by ESR is rather stable and consists of two kinds of free radicals. The results obtained by the ESR method show that both free radicals contain an unpaired electron mainly localized on N^14 nucleus. From the view-point of kinetics, the reaction mechanism of DPPH with the free radicals formed in the course of irradiation of AIBN is discussed both in the presence and absence of dissolved oxygen