This paper describes the effects of an output peaking capacitor on the propagation of an underwater streamer. A pulsed-power modulator using a magnetic-pulse-compression circuit was employed to generate 20-30-kV pulses with 2-mus pulsewidth. A point-to-plane electrode setup with 2-cm gap in tap water was used. A copper line with 0.43-mm tip diameter was used as the discharge electrode, and an aluminum plate was set in water and connected to ground. Underwater-streamer propagation was visualized by an intensified-charge-coupled-device camera with a high-speed gate. An optional output peaking capacitor was connected in parallel to the electrodes to get pulses with different rise time and higher peak voltage and current. Thin and well-distributed channels were observed when the peaking capacitor was used. In contrast, the number of streamer channels was small, and each of them was thick and bright when the peaking capacitor was removed from the circuit. It is concluded that the peaking capacitor has a favorable effect on the generation and propagation of the underwater streamer.

Effects of Output Peaking Capacitor on Underwater-Streamer Propagation

In plants, several transposable elements are conserved across species. We found a homolog of ONSEN, which is a heat-activated retrotransposon originally isolated from Arabidopsis thaliana, in Vigna. The ONSEN-like elements (VaONS) were detected in all the analyzed Japanese accessions of Vigna angularis (adzuki bean) by Southern blot analysis. However, VaONS sequences were observed to be polymorphic in the different accessions. Interestingly, extrachromosomal DNA (ecDNA) was detected in some accessions of adzuki bean, indicating the conserved heat-activation of VaONS. Furthermore, we successfully induced retrotransposition of VaONS in adzuki plant regenerated through callus. Findings of our study should provide a new tool for molecular breeding of adzuki bean.

/pdf/characterization-of-a-heat-activated-retrotransposon-in-2nr6c9aeoo.pdf

Characterization of a heat-activated retrotransposon in Vigna angularis

Natural accessions are used for studying intraspecies genetic variation in the model plant Arabidopsis thaliana in order to address fundamental questions of evolution. Transposable elements are responsible for a wide range of mutations and play significant roles in shaping a genome over evolutionary time. In the present study, we aimed to characterize ONSEN, a heat-activated long terminal repeat (LTR) retrotransposon, in natural A. thaliana accessions. Southern blot analysis demonstrated that ONSEN was present in all the studied accessions, but the copy number was diverse. Olympia-1 contained a single ONSEN copy, located in the centromere of Chromosome 3. A premature stop codon in Olympia-1 ONSEN presumably abolishes integrase activity, which in turn presumably renders the retrotransposon non-functional. Hybridization of Col-0 with Olympia-1 showed that several ONSEN copies in Col-0 were activated by heat stress and maintained their transpositional activity in the progeny.

/pdf/characterization-of-a-heat-activated-retrotransposon-in-1htvioe36d.pdf

Characterization of a heat-activated retrotransposon in natural accessions of Arabidopsis thaliana.

ONSEN is a heat-activated LTR retrotransposon in Arabidopsis thaliana. Screens to identify transcriptional regulatory factors of ONSEN revealed a SWI/SNF-like chromatin remodeling protein, DRD1, which cooperates with plant-specific RNA polymerase and is involved in RNA-directed DNA methylation. ONSEN transcript level was increased in the drd1 mutant relative to wild-type under heat stress, indicating that DRD1 plays a significant role in the silencing of activated ONSEN under the stress condition. The transcript level of HsfA2, which is directly involved in transcriptional activation of ONSEN, was not higher in the drd1 mutant than in the wild-type. Interestingly, no transgenerational transposition of ONSEN was observed in the drd1 mutant, even though DNA methylation levels were significantly reduced and expression levels were increased compared to the wild-type. These results suggest that other factors are involved in the regulation of ONSEN transposition in addition to the transcript level of ONSEN.

/pdf/drd1-a-swi-snf-like-chromatin-remodeling-protein-regulates-a-41hm601ihu.pdf

DRD1, a SWI/SNF-like chromatin remodeling protein, regulates a heat-activated transposon in Arabidopsis thaliana

Retrotransposons are mobile genetic elements which transpose via an RNA intermediate. Some retrotransposons were shown to be transcriptionally activated by biotic and abiotic stress factors, such as UV light, ozone, pathogens, wounding, and drought. Our previous study showed that underwater pulsed streamer discharge can activate retrotransposon gene PyRE1G1 of Porphyra yezoensis. Pulsed streamer discharge in water is known to generate physical phenomena such as high electric fields, current, UV, ozone, other chemically activate species, and shock waves. It is an important issue to evaluate the degree of effectiveness for each factor. In this paper, effects of either pulsed high electric field or pulsed current were investigated. Experimental results showed both of them gave sufficient results for the transcriptional activation of PyRE1G1. Expression was induced 1 h after the pulse treatment. Keywords—Porphyra yezoensis, red alga, retrotransposon gene, transcriptional activation, pulsed power, underwater pulsed discharge, pulsed electric field, pulsed current. Corresponding author: Douyan Wang e-mail address: douyan@cs.kumamoto-u.ac.jp Hirayama et al. 272

Effects of pulsed electric field and pulsed current on transcriptional activation of retrotransposon of porphyra yezoensis

Retrotransposons are mobile genetic elements that accomplish transposition via an RNA intermediate. These elements can be transcriptionally activated by stress factors, such as UV light, ozone, pathogens, wounding and drought. A red alga, Porphyra yezoensis has recently been recognized as a model plant for fundamental and applied study in marine biological science. In this paper, pulsed streamer-like discharge in liquid was used as a new stress condition, and the transcriptional levels of retrotransposon and functional genes of a red alga, Porphyra yezoensis was investigated. From the results of reverse transcription-polymerase chain reaction (RT-PCR) experiments, it is clear that the transcriptions of retrotransposon and functional genes were activated by applying pulsed streamer-like discharge.

/pdf/activation-of-retrotransposon-in-red-alga-by-underwater-40zytkp8jo.pdf

Activation of retrotransposon in red alga by underwater pulsed discharge

Summary form only given. Retrotransposons are mobile genetic elements that accomplished transposition via an RNA intermediate. These elements can be transcriptionally activated by stress factors, such as UV light, ozone, pathogens, wounding and drought. A red alga, porphyra yezoensis has recently been recognized as a model plant for fundamental and applied study in marine biological science. In this paper, pulsed streamer-like discharge in liquid was used as a new stress condition, and the transcription level of a copia-like retrotansposon gene PyEl of a red alga, porphyra yezoensis was investigated. From the results of reverse transcription-polymerase chain reaction (RT-PCR) experiments, tire transcription of PyEl was activated by applying pulsed streamer-like discharge. The results suggest that pulsed streamer-like discharge in liquid can be used as a new stress condition to activate retrotransposon genes and can provide a useful tool for insertion mutagenesis and genome research in biologv field.

S. Takio

Papers

Activation of retrotransposon in red alga by underwater pulsed discharge

Effects of pulsed electric field and pulsed current on transcriptional activation of retrotransposon of porphyra yezoensis

The Effect of Pulsed Streamer-Like Discharge in Liquid on Transcriptional Activation of Retrotransposon Genes of a Red Alga, Porphyra Yezoensis

The effectofpulsedstreamer-like discharge inliquidon transcriptional activationofretrotransposon genes of aredalga,porphyrayezoensis