Search

Centromeric satellite DNA (cen-satDNA) sequences of the Asian swamp eel (Monopterus albus) were characterized. Three GC-rich cen-satDNA sequences were detected as a 233 bp MALREP-A and a 293 bp MALREP-B localized to all chromosomes, and a 293 bp MALREP-C distributed on eight chromosome pairs. Sequence lengths of MALREP-B and MALREP-C were 60 bp larger than that of MALREP-A, showing partial homology with core sequences (233 bp). Size differences between MALREP-A and MALREP-B/C suggest the possible occurrence of two satDNA families. The presence of an additional 60 bp in MALREP-B/C resulted from an ancient dimer of 233 bp monomers and subsequent mutation and homogenization between the two monomers. All MALREPs showed partial homology with transposable elements (TEs), suggesting that the MALREPs originated from the TEs. The MALREPs might have been acquired in the Asian swamp eel, thereby promoting fixation in the species.

Sex chromosomes in some amniotes share linkage homologies with distantly related taxa in regions orthologous to squamate reptile chromosome 2 (SR2) and the snake W sex chromosome. Thus, the SR2 and W chromosomes may formerly have been part of a larger ancestral amniote super-sex chromosome. Comparison of various sex chromosomal linkage homologies in Toxicofera with those in other amniotes offers an excellent model to assess key cytological differences, to understand the mechanisms of amniote sex chromosome evolution in each lineage and the existence of an ancestral amniote super-sex chromosome. Chromosome maps of four species of Toxicofera were constructed using bacterial artificial chromosomes (BACs) derived from chicken and zebra finch libraries containing amniote sex chromosomal linkages. Different macrochromosome linkage homologies were highly conserved among Toxicofera, and at least two BACs (CH261-125F1 and CH261-40D6) showed partial homology with sex chromosomes of amniotes associated with SR2, which supports the hypothesis of an ancestral super-sex chromosome with overlaps of partial linkage homologies. The present data also suggest a possible multiple fission mechanism of an ancestral super-sex chromosome, which resulted in further development of various sex chromosomal linkages of Toxicofera based on particular properties that favored the role of sex chromosomes.

Two new furanone-containing polyketides, linfuranones B and C, were isolated from a plant-associated actinomycete of the genus Sphaerimonospora. Their structures were determined by NMR and MS spectroscopic analyses, and the absolute configurations were established by anisotropic methods and chemical degradation approaches. In silico analysis of biosynthetic genes suggested that linfuranone B is generated from linfuranone C by oxidative cleavage of the polyketide chain. Linfuranones B and C induced preadipocyte differentiation into matured adipocytes at 20-40 μM without showing cytotoxicity.

Transposable elements (TEs) are dynamic elements present in all eukaryotic genomes. They can &ldquo, jump&rdquo, and amplify within the genome and promote segmental genome rearrangements on both autosomes and sex chromosomes by disruption of gene structures. The Bovine-B long interspersed nuclear element (Bov-B LINE) is among the most abundant TE-retrotransposon families in vertebrates due to horizontal transfer (HT) among vertebrate lineages. Recent studies have shown multiple HTs or the presence of diverse Bov-B LINE groups in the snake lineage. It is hypothesized that Bov-B LINEs are highly dynamic and that the diversity reflects multiple HTs in snake lineages. Partial sequences of Bov-B LINE from 23 snake species were characterized. Phylogenetic analysis resolved at least two Bov-B LINE groups that might correspond to henophidian and caenophidian snakes, however, the tree topology differed from that based on functional nuclear and mitochondrial gene sequences. Several Bov-B LINEs of snakes showed greater than 80% similarity to sequences obtained from insects, whereas the two Bov-B LINE groups as well as sequences from the same snake species classified in different Bov-B LINE groups showed sequence similarities of less than 80%. Calculation of estimated divergence time and pairwise divergence between all individual Bov-B LINE copies suggest invasion times ranging from 79.19 to 98.8 million years ago in snakes. Accumulation of elements in a lineage-specific fashion ranged from 9 &times, 10&minus, 6% to 5.63 &times, 2% per genome. The genomic proportion of Bov-B LINEs varied among snake species but was not directly associated with genome size or invasion time. No differentiation in Bov-B LINE copy number between males and females was observed in any of the snake species examined. Incongruence in tree topology between Bov-B LINEs and other snake phylogenies may reflect past HT events. Sequence divergence of Bov-B LINEs between copies suggests that recent multiple HTs occurred within the same evolutionary timeframe in the snake lineage. The proportion of Bov-B LINEs varies among species, reflecting species specificity in TE invasion. The rapid speciation of snakes, coinciding with Bov-B LINE invasion in snake genomes, leads us to better understand the effect of Bov-B LINEs on snake genome evolution.

The taxonomic position of an endophytic actinomycete, strain GKU 157T, isolated from the roots of a jambolan plum tree (Syzygium cumini L. Skeels) collected at Khao Khitchakut National Park, Chantaburi province, Thailand, was determined using a polyphasic taxonomic approach. 16S rRNA gene sequence analysis revealed that strain GKU 157T belongs to the genus Actinomadura and formed a distinct phyletic line with Actinomadura chibensis NBRC 106107T (98.6 % similarity). Strain GKU 157T formed an extensively branched, non-fragmenting substrate mycelium and aerial hyphae that differentiated into hooked to short spiral chains of about 20 non-motile spores with a warty surface. The cell wall contained meso-diaminopimelic acid and the whole-cell sugars were galactose, glucose, madurose, mannose and ribose. The N-acyl type of muramic acid was acetyl. Mycolic acids were absent. The phospholipids included phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), phosphatidylinositol (PI), phosphatidylinositolmannoside (PIM) and two unknown phospholipids (PLs). The major menaquinone was MK-9(H6) and the predominant fatty acids were C16:0, iso-C16:0, C18:1ω9c, C18:0 and 10-methyl C18:0 (tuberculostearic acid). The genomic DNA G+C content was 73.1 mol%. A combination of DNA–DNA hybridization results and significant differences from related species in cultural, physiological and chemical characteristics indicated that strain GKU 157T represents a novel species of the genus Actinomadura, for which the name Actinomadura syzygii sp. nov. is proposed. The type strain is GKU 157T ( = BCC 70456T = NBRC 110399T).

A new spirotetronate-class polyketide, maklamicin (1), was isolated from the culture extract of an endophytic actinomycete of the genus Micromonospora. The structure and relative configuration of 1 were elucidated by interpretation of NMR and other spectroscopic data, and the absolute configuration was determined using the modified Mosher method. Maklamicin (1) showed strong to modest antimicrobial activity against Gram-positive bacteria.

A novel endophytic actinomycete, strain GMKU 367T, was isolated from roots of Thai glutinous rice plants (Oryza sativa L. ‘RD6’) collected from Pathum Thani Rice Research Center, Pathum Thani province, Thailand. Strain GMKU 367T formed cylindrical spores on aerial mycelium, but sporangium-like structures and fragmentation of substrate mycelium were not observed. The cell-wall amino acids contained meso-diaminopimelic acid, alanine, glutamic acid and acetylated muramic acid. The whole-cell sugars were arabinose, galactose, mannose, rhamnose and ribose. Major fatty acids were iso-C15 : 0, iso-C16 : 0 and C16 : 0. The diagnostic menaquinone was MK-9(H4). The polar phospholipids were phosphatidylethanolamine and hydroxyphosphatidylethanolamine. The G+C content of the genomic DNA was 71.1 mol%. Phylogenetic analyses based on 16S rRNA gene sequence data indicated that strain GMKU 367T differed from members of the family Pseudonocardiaceae. On the basis of the evidence presented in this polyphasic study, it is proposed that strain GMKU 367T represents a novel species in a new genus in the family Pseudonocardiaceae, with the name Actinophytocola oryzae gen. nov., sp. nov.; the type strain of Actinophytocola oryzae is GMKU 367T (=BCC 31372T =NBRC 105245T).

A novel endophytic actinomycete, strain GMKU 931T, was isolated from the root of a wattle tree, Acacia auriculiformis A. Cunn. ex Benth., collected at Kasetsart University, Bangkok, Thailand. Strain GMKU 931T produced short spiral chains of smooth-surfaced spores on the aerial mycelium. Lysine and meso-diaminopimelic acid were present in the cell-wall peptidoglycan. Whole-cell hydrolysates contained galactose, madurose and mannose. The predominant menaquinones were MK-9(H6) and MK-9(H8). The major fatty acids were iso-C16 : 0 and iso-C16 : 1. The major phospholipids were phosphatidylinositol and phosphatidylglycerol. A phylogenetic analysis based on 16S rRNA gene sequences suggested that strain GMKU 931T forms a distinct phyletic line within the recently proposed genus Actinoallomurus. The significant differences in phenotypic and genotypic data indicate that strain GMKU 931T represents a novel species of the genus Actinoallomurus, for which the name Actinoallomurus acaciae sp. nov. is proposed. The type strain is GMKU 931T (=BCC 28622T =NBRC 104354T =NRRL B-24610T).

A novel endophytic actinomycete, designated strain GKU 164T, was isolated from the roots of a jambolan plum tree (Syzygium cumini L. Skeels), collected at Khao Khitchakut National Park, Chantaburi province, Thailand. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain formed a distinct clade within the genus Nonomuraea , and was most closely related to Nonomuraea monospora PT708T (98.77 % 16S rRNA gene sequence similarity) and Nonomuraea thailandensis KC-061T (98.73 %). Strain GKU 164T formed a branched substrate and aerial hyphae that generated single spores with rough surfaces. The cell wall contained meso-diaminopimelic acid. The whole-cell sugars were madurose, galactose, mannose, ribose, rhamnose and glucose. The N-acyl type of muramic acid was acetyl. The predominant menaquinone was MK-9(H4) with minor amounts of MK-9(H6), MK-9(H2) and MK-9(H0). The phospholipid profile contained diphosphatidylglycerol, phosphatidylethanolamine, hydroxy-phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositolmannosides, phosphatidylmonomethylethanolamine, hydroxy-phosphatidylmonomethylethanolamine, an unidentified aminophosphoglycolipid and four unknown phospholipids. The major fatty acids were iso-C16 : 0 and 10-methyl C17 : 0. The genomic DNA G+C content was 70.4 mol%. Significant differences in the morphological, chemotaxonomical, and biochemical data together with DNA–DNA relatedness values between strain GKU 164T and type strains of closely related species, clearly demonstrated that strain GKU 164T represents a novel species of the genus Nonomuraea , for which the name Nonomuraea syzygii sp. nov. is proposed. The type strain is GKU 164T ( = BCC 70457T = NBRC 110400T).

An endophytic Streptomyces sp. GMKU 3100 isolated from roots of a Thai jasmine rice plant (Oryza sativa L. cv. KDML105) showed the highest siderophore production on CAS agar while phosphate solubilization and IAA production were not detected. A mutant of Streptomyces sp. GMKU 3100 deficient in just one of the plant growth promoting traits, siderophore production, was generated by inactivation of a desD-like gene encoding a key enzyme controlling the final step of siderophore biosynthesis. Pot culture experiments revealed that rice and mungbean plants inoculated with the wild type gave the best enhancement of plant growth and significantly increased root and shoot biomass and lengths compared with untreated controls and siderophore-deficient mutant treatments. Application of the wild type in the presence or absence of ferric citrate significantly promoted plant growth of both plants. The siderophore-deficient mutant clearly showed the effect of this important trait involved in plant-microbe interaction in enhancement of growth in rice and mungbean plants supplied with sequestered iron. Our results highlight the value of a substantial understanding of the relationship of the plant growth promoting properties of endophytic actinomycetes to the plants. Endophytic actinomycetes, therefore, can be applied as potentially safe and environmentally friendly biofertilizers in agriculture.

The novel strain GMKU 370T was isolated from roots of a Thai jasmine rice plant (Oryza sativa L. ‘KDML 105’) collected from Pathum Thani Rice Research Center, Pathum Thani province, Thailand. A phylogenetic analysis based on 16S rRNA gene sequences indicated that strain GMKU 370T formed a distinct clade within the genus Actinoallomurus. Strain GMKU 370T contained meso-diaminopimelic acid and lysine in the cell-wall peptidoglycan and galactose and madurose as whole-cell sugars. No mycolic acids were detected. The predominant menaquinones were MK-9(H6) and MK-9(H8). The polar phospholipids consisted of phosphatidylglycerol and phosphatidylinositol. These chemical properties reveal that strain GMKU 370T belongs to the genus Actinoallomurus. Strain GMKU 370T is distinct from the phylogenetically closely related type strains Actinoallomurus iriomotensis NBRC 103685T and Actinoallomurus coprocola NBRC 103688T (99.20 % 16S rRNA gene sequence similarity to both) in terms of differences in phenotypic characteristics and DNA–DNA relatedness (51 and 17 %, respectively). It is proposed that strain GMKU 370T represents a novel species of the genus Actinoallomurus, for which the name Actinoallomurus oryzae sp. nov. is proposed. The type strain is GMKU 370T ( = BCC 31373T = NBRC 105246T).