Rapid Detection of Bt Transgenic Sugarcane Using Root Tips by PCR

[Objective] This study aimed to establish an effective detection technology for rapidly identifying Bt transgenic sugarcane, promptly removing non-Bt transgenic plants and increasing breeding efficiency of Bt transgenic plants, thereby improving breeding efficiency of insect-resistant sugarcane cultivars in China. [ Method] Approximately 1 mg of root tips and other materials were crushed, placed in the bottom of PCR tubes, added successively with solution I and mineral oil, headed at 95 ℃ for 15 rain, added with solution Ⅱ, and finally added with solution III containing GBt primer for PCR. After separated by using electrophoresis on agarese gel, amplification products were observed and photographed under a gel imaging system. [ Result] Various materials treated with different concentrations of solution led to different amplification results. Specifically, the appropriate concentration of NaOH in solution I was 0.1 -0.2 mol/L; the appropriate pH value of solution II was 2. No bands were amplified from mature leaves, tender leaves and old roots of Bt transgenic sugarcane, while root tips successfully amplified 545 bp target bands. The established method was used to identify and analyze 63 hybrid seedlings of YT 91 -976 × SBR216, results showed that a total of 17 samples exhibited 545 bp bands, accounting for approximately 27% of the total number of hybrid seedlings, indicating that these 17 seedlings were Bt transgenic sugarcane plants. [ Conclusion] The rapid detection method established in this study is conducive to identifying Bt transgenic sugarcane and improving breeding efficiency of insect-resistant sugarcane lines, which provides basis for screening of other transgenic materials.

Correlation of Leaf and Root Senescence During Ripening in Dry Seeded and Transplanted Rice

Dry seeding is a resource-saving rice establishment method. With an equivalent yield, dry seeded flooded rice （DSR） has been considered as a replacement for traditional transplanted flooded rice （TFR）. However, the differences in leaf and root senescence during grain filling between DSR and TFR were seldom identified. In this study, the root length, root tip number and leaf senescence of rice varieties Huanghuazhan and Yangliangyou 6 during ripening were compared between DSR and TFR. Results showed that top three leaves in DSR had the characteristics of relatively lower SPAD value, lower N content and premature leaf senescence. In addition, both the total root length and total root tip number of DSR were significantly lower than those of TFR. In conclusion, premature and quick leaf senescence was related with inadequate root length and root tip number during ripening, which might result from the deficiency of nitrogen supply in DSR. Techniques on improving leaf nitrogen status and delaying the leaf senescence during grain-filling in DSR should be developed in future researches.

Separated root tip formation associated with a fractured tubercle of dens evaginatus: A case report

BACKGROUND Several previous studies have reported an unusual root formation in which a fractured apical fragment of an immature root continued to develop independent of the main root after trauma to an immature tooth.To date,there have been only rare reports of the continuing apical formation of the fractured root associated with dens evaginatus(DE).This paper presents a case of a separated root tip formation associated with a fractured tubercle of DE.CASE SUMMARY An 11-year-old boy was referred for gingival sinus on the buccal side of the right mandibular second premolar(tooth#45).Clinically,tooth#45 was free of caries,but there was a sign of a fractured tubercle of DE on the occlusal surface.Radiography showed that the root canal of tooth#45 was widely radiolucent.A separated root apex was found apically under the main root and was nearly completely formed with an apical orifice at the apical tip.Tooth#45 was diagnosed as tubular fracture of DE with chronic apical periodontitis.A revascularization technique was recommended to treat the tooth.At 3-mo and 1-yr follow-up,the patient remained asymptomatic.Periapical radiography revealed that the separated root tip distally drifted with closure of the apex.However,the root length and thickness of the main root did not increased.CONCLUSION Clinicians should be aware that even if tubercle of DE is fractured in an immature tooth,the root tip may be separated from the main root and completely formed.

Effects of CO_2 laser on chromosomal aberration in the root tip cells of rice

Seeds of japonica rice cv.Zhenuo 2 with twodifferent physiological states(dry seeds withwater content 13% and wet seeds soaked in thewater for 36 h)were irradiated by COlaser infour different power-densities and durations re-spectively.The treatment irradiated with 200GY ofCo γ-rays was considered as control.The flesh root tips were cut and fixed inCarnoy’s fluid for cytological examination.

Responses of Aerobic Rice (Oryza sativa L.) to Iron Deficiency

Aerobic rice has the advantage of saving water. Most published work has focused on improving its yield, while few reported on its micronutrient status. In fact, Fe deficiency is a common nutritional problem in the production of aerobic rice. Short- term hydroponic culture experiments were conducted to study the response of aerobic rice to Fe deficiency and the effect of root exudates from Fe-deficient wheat on its Fe uptake ability. The results indicate that the amount of phytosiderophores （PS） released from aerobic rice did not increase under Fe deficient conditions. The Fe（III） reducing capacity of Fe-deficient aerobic rice did not increase and the solution pH did not decrease significantly. What＇s more, no obvious swelling was observed in the root tips. Aerobic rice did not show special responses to improve their Fe nutrition under Fe deficiency as both strategy I and II plants though they were very sensitive to Fe deficiency. This may be a reason which causes Fe deficiency problem in aerobic rice. However, root exudates from Fe-deficient wheat （PSw） could improve its Fe nutrition in the presence of insoluble Fe（OH）3. This suggests that aerobic rice could utilize Fe activated by PSw.

Study on Genetic Toxicity of Solidago decurrens

[Objectives]This study was conducted to analyze the genetic toxicity of Solidago decurrens,with a view to scientifically and safely using S.decurrens.[Methods]Using commercially available S.decurrens as an experimental material,according to Vicia faba root tip micronucleus technique,V.faba root tips were treated with different doses of aqueous extract from S.decurrens for different times,and the mitotic index,frequency of micronucleus and chromosomal aberration of root tips in V.faba were detected,so as to reveal the allelopathic potential and the potential ecological risks of S.decurrens at the cellular level.[Results]The decrease in the mitotic index caused by the aqueous extract of S.decurrens was positively related to the concentration of the aqueous extract and the treatment time.The aqueous extract of S.decurrens increased the frequency of micronucleus in root tip cells of V.faba,and the increase was positively related to the concentration of the aqueous extract and the treatment time.The aqueous extract of S.decurrens caused abnormal phenomena such as chromosome bridges,chromosome fragmentation,and chromosome lag in V.faba root tip cells,and the effect of the aqueous extract on V.faba root tips had significant effects dependent on time and concentration.Above results indicate that the aqueous extract of S.decurrens inhibited and damaged the mitosis of V.faba root tip cells to some degrees,had certain genetic toxicity and had the ability to rapidly spread.[Conclusions]This study provides a theoretical basis for scientifically and rationally using S.decurrens and preventing the spread of S.decurrens.

Cytotoxicity and genotoxicity evaluation of urban surface waters using freshwater luminescent bacteria Vibrio-qinghaiensis sp.-Q67 and Vicia faba root tip

The freshwater luminescent bacteria Vibrio-qinghaiensis sp.-Q67 test and the Vicia faba root tip test associated with solid-phase extraction were applied for cytotoxicity and genotoxicity assessment of organic substances in three rivers, two lakes and effluent flows from two wastewater treatment plants （WWTPs） in Xi＇an, China. Although the most seriously polluted fiver with high chemical oxygen demand （COD） and total organic carbon （TOC） showed high cytotoxicity （expressed as TIIs0, the toxicity impact index） and genotoxicity （expressed as RMCN, the relative frequency of micronucleus）, no correlative relation was found between the ecotoxicity and organic content of the water samples. However, there was a linear correlative relation between TIIs0 and RMCN for most water samples except that from the Zaohe River, which receives discharge from WWTP and untreated industrial wastewaters. The ecotoxicity of the organic toxicants in the Chanhe River and Zaohe River indicated that cytotoxic and genotoxic effects were related to the pollutant source. The TII50 and RMCN were also found to correlate roughly to the dissolved oxygen concentration of the water. Sufficient dissolved oxygen in surface water is thus proved to be an indicator of a healthy water environmental condition.

Allium cepa root tip assay in assessment of toxicity of magnesium oxide nanoparticles and microparticles

Allium cepa bioassay had been used from decades for the assessment of toxicants and their harmful effects on environment as well as human health. Magnesium oxide（MgO） particles are being utilized in different fields. However, reports on the adverse effects of MgO nanoparticles on the environment and mankind are scarce. Hence, the toxicity of MgO particles is of concern because of their increased utilization. In the current study, A. cepa was used as an indicator to assess the toxicological efficiency of MgO nano-and microparticles（NPs and MPs） at a range of exposure concentrations（12.5, 25, 50, and100 μg/m L）. The toxicity was evaluated by using various bioassays on A. cepa root tip cells such as comet assay, oxidative stress and their uptake/internalization profile. Results indicated a dose dependent increase in chromosomal aberrations and decrease in mitotic index（MI） when compared to control cells and the effect was more significant for NPs than MPs（at p 〈 0.05）. Comet analysis revealed that the Deoxyribonucleic acid（DNA） damage in terms of percent tail DNA ranged from 6.8–30.1 over 12.5–100 μg/m L concentrations of MgO NPs and was found to be significant at the exposed concentrations. A significant increase in generation of hydrogen peroxide and superoxide radicals was observed in accordance with the lipid peroxidation profile in both MgO NPs and MPs treated plants when compared with control. In conclusion, this investigation revealed that MgO NPs exposure exhibited greater toxicity on A. cepa than MPs.