Complex Epistasis for Dobzhansky–Muller Hybrid Incompatibility in Solanum

We examined the prevalence of interactions between pairs of short chromosomal regions from one species (Solanum habrochaites) co-introgressed into a heterospecific genetic background (Solanum lycopersicum). Of 105 double introgression line (DIL) families generated from a complete diallele combination of 15 chromosomal segments, 39 (~38%) showed evidence for complex epistasis in the form of genotypic and/or allelic marker transmission distortion in DIL F₂ populations.     

Potential impacts of flooding events and stream modification on an endangered endemic plant, <Emphasis Type="Italic">Schoenoplectus gemmifer</Emphasis> (Cyperaceae)

River management often conflicts with the conservation of species in river ecosystems. In Japan, almost all river systems have been covered by concrete walls. Such river improvement works caused critical damage to river ecosystems. Here we report the ongoing extinction process of a rare aquatic plant by several consecutive heavy rains. The aquatic plant, Schoenoplectus gemmifer C. Sato, T. Maeda & Uchino, is an extremely rare endemic species that is strictly associated with springwater. The species is only found in 23 locations in Japan, including only two major habitats: Hamamatsu and Oita. We monitored the population fluctuations of S. gemmifer at three river systems in Hamamatsu. In the largest habitat, Higashikanda River, the population size of the species decreased to nearly 1/10th in 2004, due to several severe floods. Spatial and temporal records exhibit four stages of damaging process. The stepwise damages were found to be caused by a rapid flow of water accelerated by the river improvement work (made in 1985). The reproduction and growth by seeds and gemmae did not evidently cover the losses by flood washed out. In the other two rivers, one was extinct and the other is now at the risk of extinction. The modified river structures may be responsible for the near-extinction of S. gemmifer in Hamamatsu area. We propose two policies for the conservation of this species: (1) the artificial cultivation of gemmae and seedlings and (2) the modification of river structure to decrease the number of washed-out plants. In particular, it is important to decrease the water velocity at floods by some methods.     

Distribution and molecular characterization of distinct Asian populations of Bemisia tabaci (Hemiptera: Aleyrodidae) in Japan

Bemisia tabaci (Gennadius) is considered to be the most economically important pest insect worldwide. The invasive variant, the Q biotype of B. tabaci was first identified in 2004, and has caused significant crop yield losses in Japan. The distribution and molecular characterization of the different biotypes of B. tabaci in Japan have been little investigated. In this study, B. tabaci populations were sampled from the Japanese Archipelago, the Amami Archipelago and the Ryukyu Islands between 2004 and 2008, and the nucleotide sequences of their mitochondrial cytochrome oxidase I genes were determined. Bayesian phylogenetic relationship analysis provided the first molecular evidence that the indigenous Japanese populations could be separated into four distinct genetic groups. One major native population from the Japanese Archipelago, given the genetic group name Lonicera japonica, was separated into an independent group, distinct from the other genetic groups. The second major population, the Nauru biotype in the Asia II genetic group, was identified in the Amami Archipelago and the Ryukyu Islands. Two distinct minor genetic groups, the Asia I and the China, were also identified. One invasive B‐related population belonging to the Mediterranean/Asia Minor/Africa genetic group has been identified in Honshu. All lineages generated by the phylogenetic analyses were supported by high posterior probabilities. These distinct indigenous B. tabaci populations developed in Japan under geographical and/or biological isolation, prior to recent invasions of the B and Q biotypes.     

Mechanism of action of nitrous oxide gas applied as a polyploidizing agent during meiosis in lilies

Nitrous oxide gas (N₂O) can be used to produce polyploid plants, but the mechanism of action is unknown. The actin and microtubule cytoskeleton was observed in N₂O-treated microsporocytes of Lilium spp ‘Asiatic hybrid lilies’ using fluorescence microscopy after staining with DAPI, FITC-conjugated tubulin antibody, and phalloidin-conjugated Alexa Fluor 546. Additionally, microsporocytes of L. longiflorum were observed with acetocarmine staining following N₂O treatment. A typical metaphase I microtubule distribution was observed in control microsporocytes. After treatment with N₂O for 24 h, microtubules were effectively depolymerized; this prevented chromosomes from moving to the poles, resulting in chromosome retention in the center of N₂O-treated cells. Cell plate formation took place without delay, however, yielding one daughter cell with a diploid genome and another daughter without chromosomes. In addition, N₂O treatment often induced micronuclei due to aberrant chromosome separation during cytokinesis. Actin filaments in microsporocytes are insensitive to N₂O. These findings indicate that N₂O mediates polyploidization by inhibiting microtubule polymerization, but not actin filament formation, during microsporocyte meiosis.     

HCHL expression in hairy roots of Beta vulgaris yields a high accumulation of p-hydroxybenzoic acid (pHBA) glucose ester,and linkage of pHBA into cell walls

As part of a study to explore the potential for new or modified bio-product formation, Beta vulgaris (sugar beet) has been genetically modified to express in root-organ culture a bacterial gene of phenylpropanoid catabolism. The HCHL gene, encoding p-hydroxycinnamoyl-CoA hydratase/lyase, was introduced into B. vulgaris under the control of a CaMV 35S promoter, using Agrobacterium rhizogenes LBA 9402. Hairy root clones expressing the HCHL gene, together with non-expressing clones, were analysed and revealed that one expression-positive clone accumulated the glucose ester of p-hydroxybenzoic acid (pHBA) at about 14% on a dry weight basis. This is the best yield achieved in plant systems so far. Determination of cell-wall components liberated by alkaline hydrolysis confirmed that the ratio of pHBA to ferulic acid was considerably higher in the HCHL-expressing clones, whereas only ferulic acid was detected in a non-expressing clone. The change in cell-wall components also resulted in a decrease in tensile strength in the HCHL-expressing clones.     

Using porphyritic andesite as a new additive for improving hydrolysis and acidogenesis of solid organic wastes

The effects of porphyritic andesite on the hydrolysis and acidogenesis of solid organic wastes were investigated by batch and continuous experiments using a rotational drum fermentation system. The results of the batch experiment show that if porphyritic andesite (1%, 3%, and 5% reactants) is added initially, the pH level increases and hydrolysis and acidogenesis are accelerated. The highest surface based hydrolysis constant (26.4 × 10⁻³ kg m⁻² d⁻¹) and volatile solid degradation ratio (43.3%) were obtained at a 1% porphyritic andesite addition. In the continuous experiment, porphyritic andesite elevated the first order hydrolysis constant from 13.10 × 10⁻³ d⁻¹ to 18.82 × 10⁻³ d⁻¹. A particle mean diameter reduction rate of 33.05 μm/d and a volatile solid degradation rate of 3.53 g/L d⁻¹ were obtained under the hydraulic retention time of 4, 8, 12 and 16 d.     

A 5000-YEAR FOSSIL RECORD OF LARVAL SHELL MORPHOLOGY OF SUBMARINE CAVE MICROSHELLS

A 5000-year fossil series of minute submarine cave bivalves was studied using morphometric and evolutionary analyses. The obtained results indicate that the shapes of larval shells of studied species were labile, whereas the size of the larval shell was stable in each species studied. This result is different than that previously reported in most other studies in which size change is more common than shape change. This unique evolutionary pattern of these bivalves might be attributed to their refugial lifestyle.