Impact of Low-Energy Ion Beam Implantation on the Expression of Ty1-copia-like Retrotransposons in Wheat(Triticum aestivum)

Retrotransposon-like elements are major constituents of most eukaryotic genomes. For example, they account for roughly 90% of the wheat （Triticum aestivum） genome, Previous study on a wheat strain treated by low-energy N^＋ ions indicated the variations in AFLP （Amplified Fragment Length Polymorphism ） markers, One such variation was caused by the re-activation of Tyl-copia-like retrotransposons, implying that the mutagenic effects of lowenergy ions might work through elevated activation of retrotransposons, In this paper an expression profile of Tyl-copia-like retrotransposons in wheat treated by low-energy N^＋ ions is reported, The reverse transcriptase （RT） domains of these retrotransposons were amplified by reverse-transcriptional polymerase chain reaction （RT-PCR） and sequentially cloned, 42 and 65 clones were obtained from the treated （CL） and control materials （CK）, respectively, Sequence analysis of each clone was performed by software. Phylogeny and classification were calculated responding to the sequences of the RT domains. All the results show that there is much difference in the RT domain between the control sample and the treated sample, Especially, the RT domains from the treated group encode significantly more functional ORF （open reading frames） than those from the control sample, This observation suggests that the treated sample has higher activation of retrotransposons, possibly as a consequence of low-energy ion beam irradiation, It also suggests that retrotransposons in the two groups impact the host gene expression in two different ways and carry out different functions in wheat cells.

Analysis of a Partial Male-Sterile Mutant of Arabidopsis thaliana Isolated from a Low-Energy Argon Ion Beam Mutagenized Pool

A screen for Arabidopsis fertility mutants, mutagenized by low-energy argon ion beam, yielded two partial male-sterile mutants tc243-1 and tc243-2 which have similar phenotypes. tc243-2 was investigated in detail. The segregation ratio of the mutant phenotypes in the M2 pools suggested that mutation behaved as single Mendelian recessive mutations, tc243 showed a series of mutant phenotypes, among which partial male-sterile was its striking mutant characteristic. Phenotype analysis indicates that there are four factors leading to male sterility, a. Floral organs normally develop inside the closed bud, but the anther filaments do not elongate sufficiently to position the locules above the stigma at anthesis, b. The anther locules do not dehisce at the time of flower opening （although limited dehiscence occurs later）, c. Pollens of mutant plants develop into several types of pollens at the trinucleated stage. as determined by staining with DAPI （4＇,6-diamidino-2-phenylindole）. which shows a variable size. shape and number of nucleus. d. The viability of pollens is lower than that of the wild type on the germination test in vivo and vitro.

Preliminary Studies on Base Substitutions and Repair of DNA Mismatch Damage Stimulated by Low Energy N^+ Ion Beam Implantation in Escherichia coli

Ever since the low energy N+ ion beam has been accepted that the mutation effects of ionizing radiation are attributed mainly to direct or indirect damage to DNA. Evidences based on naked DNA irradiation in support of a mutation spectrum appears to be consistent, but direct proof of such results in vivo are limited. Using mutS, dam and/or dcm defective Eschericha coli imitator strains, an preliminary experimental system on induction of in vivo mutation spectra of low energy N+ ion beam has been established in this study. It was observed that the mutation rates of rifampicin resistance induced by N+ implantation were quite high, ranging from 9.2 x 10~8 to 4.9× 10~5 at the dosage of 5.2×1014 ions/cm2. Strains all had more than 90-fold higher mutation rate than its spontaneous mutation rate determined by this method. It reveals that base substitutions involve in induction of mutation of low energy nitrogen ion beam implantation. The mutation rates of mutator strains were nearly 500-fold (GM2929), 400-fold (GM5864) and 6-fold larger than that of AB1157. The GM2929 and GM5864 both lose the ability of repair DNA mismatch damage by virtue of both dam and dcm pathways defective (GM2929) or failing to assemble the repair complex (GM5864) respectively. It may explain the both strains had a similar higher mutation rate than GM124 did. It indicated that DNA cytosine methylase might play an important role in mismatch repair of DNA damage induced by N+ implantation. The further related research were also discussed.

Evidence for Base Substitutions and Repair of DNA Mismatch Damage Induced by Low Energy N^+ Ion Beam Implantation in E. coli

Ever since the low energy N + ion beam has been accepted, the mutations of ionizing radiation are attributable mainly to avoidance of DNA damages repair. Evidences based on in vivo proof results are limited. Using the E.coli wild type and mutator strains, the mutant frequencies suggest that base substitutions in rpoB gene are induced by the N + implantation. A highly conserved region is selected to get the direct evidence for base substitutions by sequence of the high fidelity PCR amplification products in mutants. Most of the mutants (90.9%, 40/44) have at least one base substitution in the amplification region. The evidences for CG to TA (55%, 22/40), AT to GC (20%, 8/40) and TA to CG (5%, 2/40) transitions are identified. The transversions are AT to TA (15%, 6/40) and GC to CG (5%, 2/40). It is suggested that DNA cytosine methylase might play an important role in mismatch repair of DNA damage induced by N + implantation by analysis of the mutant frequencies of mutator strains.

Breeding of High-Yield Salinomycin-Producing Streptomyces albus Strains by Low Energy N^+ Ion Beam Irradiation

[Objective] This study aimed to explore the mutagenesis effects of N＋ ion beam implantation on Streptomyces a/bus and obtain high-yield salinomycin- producing mutant strain. [ Method ] Streptomyces a/bus strain S-11-04 was mutated with different doses of N ＋ implantation. The effects of low energy N ＊ implantation on the survival rate, colony morphology and salinomycin-producing ability were investigated. [ Result] The results showed that low energy N ＋ implantation can efficiently improve the positive mutation rate of Streptomyces albus; 13 mutant strains with high yield of salinomycin were isolated; to be specific, mutant strain N3- 6 has relatively good genetic stability with four continuous generations, and the titres of salinomycin were increased by 41% in the shake-flask culture and 20.5% in mass production compared with the control. [ Conclusion ] N ＋ ion beam irradiation is an effective method to obtain high-yield salinomycin-producing Streptomy- ces albus strain.

Nonlinear simulation of multiple toroidal Alfvén eigenmodes in tokamak plasmas

Nonlinear evolution of multiple toroidal Alfven eigenmodes(TAEs) driven by fast ions is self-consistently investigated by kinetic simulations in toroidal plasmas.To clearly identify the effect of nonlinear coupling on the beam ion loss,simulations over single-n modes are also carried out and compared with those over multiple-n modes,and the wave-particle resonance and particle trajectory of lost ions in phase space are analyzed in detail.It is found that in the multiple-n case,the resonance overlap occurs so that the fast ion loss level is rather higher than the sum loss level that represents the summation of loss over all single-n modes in the single-n case.Moreover,increasing fast ion beta β_h can not only significantly increase the loss level in the multiple-n case but also significantly increase the loss level increment between the single-n and multiple-n cases.For example,the loss level in the multiple-n case for β_h=6.0% can even reach 13% of the beam ions and is 44% higher than the sum loss level calculated from all individual single-n modes in the single-n case.On the other hand,when the closely spaced resonance overlap occurs in the multiple-n case,the release of mode energy is increased so that the widely spaced resonances can also take place.In addition,phase space characterization is obtained in both single-n and multiple-n cases.

Development of a SCAR Marker for Discrimination of a Thai Jasmine Rice (<i>Oryza sativa</i>L. cv. KDML105) Mutant, BKOS6, and Associated with Purple Color Trait in Thai Jasmine Rice-Related Varieties

The potential of SCAR marker for discrimination of a Thai jasmine rice (Oryza sativa L. cv. KDML 105) mutant, BKOS6, obtained from ion-beam-induced mutation, was evaluated. The improved rice variety, BKOS6, exhibited many remarkable characteristics which fitted the multiple cropping system characteristics of progressive agriculture including photoperiod insensitivity, early flowering, short in stature, and purple pigment accumulation in pericarp. The BKOS6 rice grain extract has already been proved that it exhibited higher antioxidant properties than the KDML 105 and other tested rice grain extracts. In this study, the BKOS6 specific SCAR marker was developed by HAT-RAPD analysis of rice genomic DNA. The marker was successfully used to identify BKOS6 variety and its hybrid varieties containing purple pigment accumulation in plant tissues. Moreover, it was found that this marker could be used to detect other purple pigmented rice varieties that genetically related to Thai jasmine rice. Recently, a wide variety of anthocyanin-based foods are believed to provide significant potential health benefits, and become more attractive. KDML 105 is also a Thai premier fragrant rice variety which is one of the main varieties of country’s rice export. Thus this molecular marker could be useful for commercial and breeding purposes of BKOS6 mutant and other developed varieties from KDML 105 which contain anthocyanin accumulation.

N^+离子束注入玉米自交系变异的生物学效应与分子标记分析

采用不同能量和剂量的N+离子束,对郑58、昌7-2和K12玉米自交系的干种子进行处理,结果表明,发芽率、发芽势和农艺性状变异都有很大差异,筛选出的N+离子束注入玉米自交系最佳诱变能量30 KV和剂量7×1016N+/cm2。同时利用10对SSR引物对玉米自交系进行扩增,共检测到39个等位基因,每对引物可检测等位基因2～5个,平均3.9个。根据SSR分子标记聚类分析,诱变能量30 kV和剂量7×1016 N+/cm2是诱变效果最佳的。3个自交系中郑58对N+离子束诱导引起的变异最敏感,N+离子束注入玉米自交系变异的生物学效应与分子标记分析结果基本一致。

小麦N离子束注入诱变育种的应用研究

为了探寻新的育种手段,解决目前小麦常规育种中普遍存在的种质资源匮乏问题以提升育种效率,开展了小麦N离子束注入诱变育种与常规育种相结合的应用研究。以N离子不同剂量注入小麦品种连麦6号籽粒进行诱变处理,经过M_1代损伤效应分析,M_2代突变体的分类统计和筛选,M_3代常规系谱法稳定性鉴定,考察了N离子注入对连麦6号农艺性状的诱变效应。结果表明:N离子注入对连麦6号的诱变效应在M_1代显著地表现在株高、结实率、抽穗期和成株率上,M_2代的突变率随N离子注入剂量的增加而提高,由低到高3种剂量处理的突变率分别为5.38%、8.98%和11.02%,筛选出的3个超亲变异性状(矮秆多蘖、早熟性、大穗)在M_3代因不同的剂量处理其重复稳定性存在明显差异;试验明确了不同剂量的离子注入处理对小麦生理性状影响的变异效应不同。

N^+离子束和^(60)Coγ射线辐照引起脂质过氧化产物及调节酶活性变化的比较研究

以烟草愈伤组织中超氧化自由基（O2）、过氧化氢（H2O2）和丙二醛（MDA）及超氧岐化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）的产率和含量及活性为生物效应指标，比较研究了N＋离子束和60Coγ射线的辐照效应。结果表明：N＋离子束（E＝20keVD＝（1－6）×1015N＋／cm2）和γ射线（D＝135－315Gy）辐照烟草愈伤组织能够引起O2产率、H2O2和MDA含量的升高，并且升高的趋势随辐照剂量的增多而增加；同时也能够引起SOD、POD和CAT活性的变化，在N＋离子束D＝（1－3）×1015N＋／cm2和γ射线D＝135－180Gy辐照时，SOD、POD和CAT的活性增强，并且随辐照剂量的增多而增强。在N＋离子束D＝（3－6）×1015N＋／cm2，γ射线D＝180－315Gy辐照时，SOD、POD和CAT酶活性下降，其活性下降趋势随辐照剂量的增大而增强。讨论了N＋离子束辐照作用的特点。

用LZD-1000离子机注入N^+束诱变狗牙根的研究

为转变我国狗牙根优良品系的依赖性及克服常规育种的困难,通过LZD-1000离子注入机将N+束注入狗牙根干种子,研究N+束对种子发芽能力的变化。结果表明,N+束可激发狗牙根种子萌发吸水,对提高种子萌发率有显著促进作用,注入处理的种子发芽率和播种品质均比对照有不同程度的提高,注入离子量为0.8×1016个/cm2时,种子发芽率最高为34%。20 keV和0.8×1016个/cm2是N+束注入诱变狗牙根育种最有效的诱变参数,可以诱使狗牙根种子萌发状况发生较大的变异,进而扩大了狗牙根种质的多态性,提高了选育优良种质的机率。

低能N^+离子束辐照甜叶菊种子的当代效应研究

用不同剂量低能N+离子注入甜叶菊种子后,观察并记录种子发芽率、幼苗和移栽植株性状及糖苷含量的影响。结果表明低剂量的氮离子束能促进甜叶菊发芽,高剂量则抑制其发芽;随着辐照剂量的增高,移栽植株株高、糖苷含量等主要指标出现了先下降后升高的"马鞍型"曲线;经辐照后出现了植株高、叶片多、叶面积大、糖苷含量高的有益变异,为进一步品种选育和诱变机理研究奠定基础。

氮离子束轰击对电弧离子镀TiN膜层的作用

电弧离子镀膜层中"大颗粒"的存在,降低了膜层质量,限制了其进一步应用。采用俄罗斯UVN0.5D2I离子束辅助沉积电弧离子镀设备,对高速钢W18Cr4V上沉积的TiN膜层进行了氮离子束轰击。结果表明:TiN膜层表面"大颗粒"完全消失,凹坑浅而平整,粗糙度降低。膜层中较软的Ti和Ti2N向TiN转变,TiN(111)取向逐渐减弱,而(200)取向逐渐增强。膜层的显微硬度由原来的1980HV1N升高到2310HV1N。

N^+离子束注入对玉米幼苗生长及POD同工酶的影响

以郑单 95 8和农大 1 0 8及其各自交系为试材 ,研究了离子束注入后对M1 苗期性状及过氧化物同工酶的影响 ,结果表明 :离子束注入后的各处理种子发芽指数、出苗率都低于对照 ,其中徐 1 78和黄C的发芽指数分别只有对照的 60 %和 5 0 % ;出苗率以昌 7- 2下降最多 ,只有对照的 43%。从POD同工酶酶谱看 ,胚、幼芽和苗期叶片 ,均检测出同工酶不同程度、不同形式的改变 。

低能N^+离子束诱导小麦农艺性状变异的细胞学基础

用剂量不同的低能(E=30kev)N+离子注入小麦稳定品系CH3286干种子,对M3代植株的株高、生育期(抽穗期)、抗病性、穗型和产量等农艺性状的变异进行了分析,对产生这种诱变效应的细胞学机制进行了细致的研究。结果表明,N+离子注入对小麦农艺性状的影响主要表现在生育期(抽穗期)、株高、穗型和产量性状,对抗病性改善不大。对产量性状的影响主要表现在对千粒重、株粒重、株粒数的影响,使千粒重极显著的降低(F=0.01),而使株粒重和株粒数显著的增加(F=0.05),对穗长、穗颈长、剑叶长、结实小穗数的影响不大。低能N+离子束注入,影响M1代小麦植株花粉母细胞减数分裂,使中期Ⅰ细胞的染色体配对频率降低,单价体频率增高,出现环状染色体、染色体断臂和多价体;在减数分裂后期和末期细胞中,染色体桥、落后染色体、染色体断片和微核等染色体畸变频率比未注入小麦显著增高,其中以染色体断片和微核居多;染色体的畸变频率与离子注入剂量呈正相关,剂量越大,畸变频率越高,变异类型也相对较多。低能N+离子束诱导花粉母细胞减数分裂行为异常是其诱导小麦农艺性状变异的重要原因,并呈明显的剂量效应。

低能N^+注入选育凝结芽孢杆菌高效生防菌株

为了进一步提高凝结芽孢杆菌NJYHHWG 877005菌株的拮抗性能,获得生防效果更好的菌株,利用低能N^+注入菌株进行诱变,并通过平板对峙培养对诱变处理后的菌株进行筛选。结果表明,菌株存活率曲线遵循N^+注入生物效应的马鞍型曲线,根据其存活率及突变率确定N^+最佳注入能量为15 ke V,最佳注入剂量为140×10^(13)个/cm^2。通过筛选获得1株具有良好性状的突变株L1,芽孢形成率达77.42%,对灰葡萄孢霉菌的抑制率高达87.81%,分别较原始出发菌株提高了23.79、11.71个百分点,且连续传代培养8次,遗传稳定性良好。

离子束介导玉米DNA的苜蓿变异株AFLP分析

为了培育高产优质苜蓿新品种,利用N+束介导方法将玉米DNA导入苜蓿种子,在当代获得了多种变异植株。采用AFLP分子标记技术,对株高、茎粗、分蘖数差异显著的5种变异植株(3-8、4-12、4-13、4-25、4-26)的基因组DNA进行多态性分析,结果表明,苜蓿变异植株与对照苜蓿间的AFLP扩增图谱相比,分别检测到16、14、12、20、13条差异带,差异率分别为6.3%、5.1%、4.4%、7.1%、4.7%,变异株与对照苜蓿基因组DNA多态性存在明显差异;变异株4-25中检测到与阳性对照玉米一致的2条DNA目的带,为离子束介导玉米DNA转化苜蓿提供了分子证据。

激光辐照对离体质粒DNA的断裂效应

利用低功率的Ｈｅ－ Ｎｅ 激光辐照离体质粒ＤＮＡ，并用离子束和紫外线为对照，分析了质粒ＤＮＡ的单双链断裂效应。结果表明：Ｈｅ－ Ｎｅ 激光辐照可诱发质粒ＤＮＡ 断裂，且断裂频率随辐照剂量增大而提高；Ｈｅ－ Ｎｅ 激光辐照后的质粒超螺旋双链ＤＮＡ存活率剂量曲线不同于紫外线和氮离子束。Ｈｅ－ Ｎｅ 激光诱发双链断裂的频率低于氮离子束和紫外线。