A molecular analysis of desiccation tolerance mechanisms in the anhydrobiotic nematode Panagrolaimus superbus using expressed sequenced tags

<p>Abstract</p> <p>Background</p> <p>Some organisms can survive extreme desiccation by entering into a state of suspended animation known as anhydrobiosis. <it>Panagrolaimus superbus </it>is a free-living anhydrobiotic nematode that can survive rapid environmental desiccation. The mechanisms that <it>P. superbus </it>uses to combat the potentially lethal effects of cellular dehydration may include the constitutive and inducible expression of protective molecules, along with behavioural and/or morphological adaptations that slow the rate of cellular water loss. In addition, inducible repair and revival programmes may also be required for successful rehydration and recovery from anhydrobiosis.</p> <p>Results</p> <p>To identify constitutively expressed candidate anhydrobiotic genes we obtained 9,216 ESTs from an unstressed mixed stage population of <it>P. superbus</it>. We derived 4,009 unigenes from these ESTs. These unigene annotations and sequences can be accessed at <url>http://www.nematodes.org/nembase4/species_info.php?species=PSC</url>. We manually annotated a set of 187 constitutively expressed candidate anhydrobiotic genes from <it>P. superbus</it>. Notable among those is a putative lineage expansion of the <it>lea </it>(late embryogenesis abundant) gene family. The most abundantly expressed sequence was a member of the nematode specific <it>sxp/ral-2 </it>family that is highly expressed in parasitic nematodes and secreted onto the surface of the nematodes' cuticles. There were 2,059 novel unigenes (51.7% of the total), 149 of which are predicted to encode intrinsically disordered proteins lacking a fixed tertiary structure. One unigene may encode an exo-β-1,3-glucanase (GHF5 family), most similar to a sequence from <it>Phytophthora infestans</it>. GHF5 enzymes have been reported from several species of plant parasitic nematodes, with horizontal gene transfer (HGT) from bacteria proposed to explain their evolutionary origin. This <it>P. superbus </it>sequence represents another possible HGT event within the Nematoda. The expression of five of the 19 putative stress response genes tested was upregulated in response to desiccation. These were the antioxidants <it>glutathione peroxidase, dj-1 </it>and <it>1-Cys peroxiredoxin</it>, an <it>shsp </it>sequence and an <it>lea </it>gene.</p> <p>Conclusions</p> <p><it>P. superbus </it>appears to utilise a strategy of combined constitutive and inducible gene expression in preparation for entry into anhydrobiosis. The apparent lineage expansion of <it>lea </it>genes, together with their constitutive and inducible expression, suggests that LEA3 proteins are important components of the anhydrobiotic protection repertoire of <it>P. superbus</it>.</p

BEAM DIAGNOSTICS FOR RIBF IN RIKEN

The Radioisotope Beam Factory (RIBF) at RIEKN started its operation in the end of 2006 with the aim of conducting systematic studies on the physics of radioactive isotopes. The simultaneous use of five accelerators in series necessitates precise measurement of beam properties such as beam intensities, beam energies, and bunch lengths. Hence, a beam diagnostic system plays an important role in the efficient and stable operation of RIBF. In this paper, we provide a brief summary of the conventional beam monitors used during the daily operations of RIBF. In addition, new non-destructive monitors that have been developed bearing in mind forthcoming intensity upgrades are described.IMP;Chinese Academy of Science

Charge stripping of ^{238}U ion beam by helium gas stripper

Development of a nondestructive, efficient electric-charge-stripping method is a key requirement for next-generation high-intensity heavy-ion accelerators such as the RIKEN Radioactive-Isotope Beam Factory. A charge stripper employing a low-Z gas is an important candidate applicable to high-intensity uranium beams for replacing carbon-foil strippers. In this study, a high-beam-transmission charge-stripping system employing helium gas for ^{238}U beams injected at 10.8  MeV/u was developed and demonstrated for the first time. The charge-state evolution measured using helium in a thickness range of 0.24–1.83  mg/cm^{2} is compared with theoretical predictions. Energy attenuation and energy spread due to the helium stripper are also investigated

CONSISTENCY IN MEASUREMENT OF BEAM PHASE AND INTENSITY USING LOCK-IN AMPLIFIER AND OSCILLOSCOPE SYSTEMS

The phase probes (PPs) are installed in all cyclotrons and beam transport lines of RIBF, and the beam-bunch signals that are detected nondestructively by these PPs are used for tuning of isochronism of cyclotrons and for monitoring the beam phase and beam intensity. We mainly use a newly developed system that incorporates a lock-in amplifier (LIA) for those tuning and monitoring; however, a conventional measurement method using an oscilloscope (OSC) system is also used. In this study, we investigated the consistency in the measurements carried out using LIA and OSC systems by FFT analyzing the observed data. Additionally, we investigated the measurement accuracy of LIA and OSCIMP;Chinese Academy of Science

STABLE OPERATION OF RF SYSTEMS FOR RIBF

At RIKEN RI-Beam Factory (RIBF), very heavy ion beams like uranium are accelerated up to 345 MeV/u by the RIKEN heavy ion linac (RILAC) and four ring cyclotrons, the RIKEN Ring Cyclotron (RRC), the fixedfrequency ring cyclotron (fRC), the intermediate-stage ring cyclotron (IRC), and the superconducting ring cyclotron (SRC) [1]. In order to provide high intensity beams up to 1 pμA, all the RF systems must be stable enough for a long term (a few weeks) within ± 0.1% in voltages and ±0.1 degrees in phases. For a stable operation of RIBF, we have started to investigate a degree of stability of the RF systems using a newly developed monitoring system [2]. The efforts to improve the stability will be described.IMP;Chinese Academy of Science

STATUS OF RIBF ACCELERATORS AT RIKEN

Recent achievements and upgrade programs in the near future at RIKEN Radioactive Isotope Beam Factory (RIBF) are presented. The beam intensity and available ion species are increasing at RIBF, owing to the continuous efforts that have been made since the first beam in 2006. So far, we accelerated deuteron, helium, nitrogen, oxygen, aluminum, calcium, krypton, and uranium beams with the superconducting ring cyclotron, SRC. The extracted beam intensities reached 1,000 pnA for the helium and oxygen beams. From the operational point of view, however, the intensity of the uranium beam should be much increased. We are, therefore, constructing a new injector linac for the RIBF, consisting of a superconducting ECR ion source, RFQ, and DTL, which will be commissioned in this fiscal year. By using this injector, we also aim at independent operation of the RIBF and GARIS facility for super-heavy element synthesis.IMP;Chinese Academy of Science