ATM/ATR-dependent Tyr15 phosphorylation of cyclin-dependent kinases in response to hydroxyurea in Vicia faba root meristem cells

DNA damage or stalled replication forks activate cell cycle checkpoints. However, the regulation of metabolic pathways that are responsible for maintenance of genome integrity in plants is still largely unknown. Present research on Vicia faba root meristem cells indicates that inhibitory phosphorylation of cyclin-dependent kinases (Cdks) at Tyr15 plays a prominent role during blockage of cell cycle in response to genotoxic stress. Phosphorylation of P-loop in Cdks takes place in ATM/ATR-dependent manner. Although, Tyr15 phosphorylation upon hydroxyurea (HU) treatment was found in most cells classified to G1 and S phase, interestingly, the number of phoshpo-Tyr15-positive cells decreases in G2 phase. Presented data confirm much similarity in regulation of Cdks functions under genotoxic stress between plants and animals; however, they may also substantiate evolutionarily developed differences especially in regulation of G2/M transition between these two kingdoms.     

Beta-carbolines as specific inhibitors of cyclin-dependent kinases

Harmine (3), 7-fluoro-1-methyl beta-carboline (35) and 1-(5-methyl-imidazol-4-yl) beta-carboline (41) were potent and specific inhibitors of cyclin-dependent kinases. The degree of aromaticity of the tricyclic ring and the positioning of substituents are important for inhibitory activity. While most beta-carbolines inhibited CDK2 and CDK5 to the same extent, selective inhibition against CDK2 was observed in 1-(2-chlorophenyl)- (12), 1-(2-fluorophenyl)- (15), and 1-(2-chloro-5-nitrophenyl)- (28) beta-carbolines.     

环磷酰胺诱发蚕豆体细胞遗传损伤的研究

利用蚕豆根尖研究环磷酰胺的遗传毒性效应, 结果表明:环磷酰胺(0.1~5.0 mg/mL)能够降低蚕豆根尖细胞有丝分裂指数, 使根尖细胞中具有微核、核出芽及核固缩的细胞明显增多, 并诱发染色体结构和行为异常, 产生染色体断片、滞后和桥。环磷酰胺处理组根尖中具有核固缩和微核的细胞数呈剂量依赖性增加, 且与作用时间呈正相关, 而分裂指数的降低也具有剂量和时间效应关系。研究结果表明, 低浓度长时间接触或高浓度短时间接触环磷酰胺均可产生遗传毒害, 因此, 有关的作业人员应注意防护。     

土荆芥挥发油对蚕豆根尖细胞的氧化损伤

土荆芥是一种入侵植物,对周围植物具有较强的化感潜力.采用培养皿土培法和培养皿滤纸法,分别模拟土荆芥挥发油通过淋溶和挥发两条途径对蚕豆根尖细胞膜脂过氧化和抗氧化酶活性的影响,并分析了挥发油诱导的细胞凋亡.结果表明:在培养皿土培和培养皿滤纸处理中,在处理前期(24 h),蚕豆根尖细胞超氧化物歧化酶、过氧化物酶和过氧化氢酶的活性均随土荆芥挥发油剂量的增大呈先升高后降低的趋势;根尖丙二醛含量随处理时间的延长和处理剂量的增大呈上升趋势.在处理中期(48 h)和处理后期(72 h),出现了典型的DNALadder条带,表明土荆芥挥发油可诱导蚕豆根尖细胞凋亡,并且随着挥发油剂量的增大和处理时间的延长,细胞凋亡程度加剧.土荆芥挥发油可以通过淋溶和挥发两种途径作用于周围植物,使受体植物的膜脂过氧化程度加剧,抗氧化酶活性受到抑制,诱导根尖细胞发生氧化损伤和细胞凋亡,从而抑制周围植物生长.而且,当挥发油以淋溶途径进入土壤时,蚕豆根尖抗氧化酶活性整体较高,DNA损伤程度较小,土荆芥挥发油通过挥发途径的化感作用大于通过淋溶途径.     

表面活性剂、酸雨和Cd^2＋复合污染对蚕豆胚根细胞核的毒性

用蚕豆根尖微核技术研究了Cd^2+单因子以及与表面活性剂、模拟酸雨复合污染时对植物细胞的毒性作用。结果表明,Cd^2+浓度在0～10．0mg·L^-1范围内,对蚕豆胚根细胞微核的形成有强烈的诱导作用,Cd^2+浓度6．0mg·L^-1时的细胞微核率为13．85‰,对照组的微核率为4．53‰,此时污染影响指数(PI)为3．06;当环境中存在表面活性剂LAS1．0mg·L^-1或pH值降到4．5和3．5时,同-Cd^2+浓度下,蚕豆根尖细胞微核率、PI降低,同时伴有核变形,细胞中颗粒物增多,胚根组织不容易分散等症状,根的生长受到抑制,说明表面活性剂、酸雨对Cd^2+的毒性有协同作用。pH3．5的酸雨环境中Cd^2+对蚕豆细胞的损伤程度比pH4．5酸雨环境高,在检测高浓度、强毒性污染物的致突变效应时,应作至少3个稀释倍数,找出蚕豆根尖细胞最高微核率及PI。     

Uptake of tritiated thymidine in the root tip meristem of Vicia faba (L)

The use of tritium-labeled thymidine (3H-TdR) in biological research made it necessary to develop a quick and accurate method for determination of tritium activity in tissue. After 3H-TdR incorporation into the root tip meristem of Vicia faba, total 3H activity as well as 3H-DNA activity was measured by liquid scintillation counting. The incorporation rate of 3H-TdR using various parameters was examined-for example, the amount of incorporated 3H-TdR as a function of duration of treatment or as a function of thymidine concentration in the nutrient solution. The experimental results together with other data allow the calculation of the average number of incorporated thymidine molecules per labeled cell nucleus. This is necessary to interpret quantitatively the biological effects of incorporated radionuclides.     

Vicia faba root tip micronucleus test on the mutagenicity of water-soluble contents of cigarette smoke

The possible mutagenicity of the water-soluble contents of cigarette smoke (WSCS) was evaluated by using the Vicia faba root tip micronucleus test. The results showed significant changes in micronucleus frequency which were caused by each different concentration of WSCS. This indicates that the Vicia faba root tip micronucleus test might be used as one kind of mutagenic detection method for cigarette smoke. A comparative evaluation on the mutagenicity of 10 brands of cigarettes was carried out. Results confirmed that various degrees of mutagenicity were found for all of the brand cigarettes, among them, Huaihai was the highest, while Camellia was the lowest. The micronucleus frequencies were reduced by adding tea polyphenol, nicotinamide adenine, vitamin C and sodium selenite to the WSCS. The results suggest that these added substances might reduce the genetic injury induced by cigarette smoke.     

Low temperature between conditioning and challenge treatment prevents the 'adaptive response' of Vicia faba root tip meristem cells.

When the temperature during intertreatment time (2 h) between conditioning and challenge treatment of Vicia faba root tip meristems with either triethylenemelamine or maleic hydrazide was reduced from 24 degrees C to 12 degrees C no adaptive response occurred any more. The yield of metaphases with chromatid aberrations under these circumstances was similar to that observed after challenge treatment alone, i.e., no reduction occurred. This indicates that the metabolic state of the cells is of critical importance for the presence or absence of adaptive responses.     

SO2对蚕豆根尖细胞微核的诱导作用

应用蚕豆根尖微核试验,对SO2的遗传毒性效应进行了研究。结果表明：一定浓度范围内（0.108-14.00mg/m^3）,蚕豆根尖微核细胞数与SO2浓度间呈正相关,太原市大气污染严重的冬季采暖期根尖细胞微核率明显高于非采暖期;SO2浓度0.604mg/m^3处理24h和48h或2.80-28.00mg/m^3熏气处理4h可使蚕豆根尖中具有微核的细胞数明显增加,结果表明,低浓度SO2较长时间接触或高浓度短期接触均可引起蚕豆根尖细胞遗传物质的损伤,应用蚕豆根尖细胞微核实验可对大气SO2污染进行生物监测。SO2（2.80-28.00mg/m^3）熏气实验中,接触时间延长能导致根尖细胞微核率下降,2.80mg/m^3熏气组下降较快,14.00mg/m^3熏气组下降较慢,研究结果提示,在运用蚕豆根尖微核实验监测环境SO2污染时要考虑蚕豆的染毒方式,避免假阴性结果的出现。     

Clastogenic and physiological response of chromosomes to nine pesticides in the Vicia faba in vivo root tip assay system

9 common pesticides were assayed for clastogenic and physiological activity using Vicia faba as a eukaryotic, whole-organism, test system. The compounds tested included the insecticides acephate, demeton, monocrotophos, parathion-methyl, and trichlorfon; the fungicides captan and folpet; and the herbicides bromacil and simazine. The chemicals have been grouped according to relative genotoxicity (strongly positive: demeton, parathion-methyl; positive: folpet, acephate, monocrotophos, captan; weakly positive: bromacil, trichlorfon, simazine). The results were compared with those reported from other assay systems.     

表面活性剂、酸雨和Cd2+复合污染对蚕豆胚根细胞核的毒性

用蚕豆根尖微核技术研究了Cd²⁺单因子以及与表面活性剂、模拟酸雨复合污染时对植物细胞的毒性作用.结果表明,Cd²⁺浓度在0～10.0mg·L^-1范围内,对蚕豆胚根细胞微核的形成有强烈的诱导作用,Cd²⁺浓度6.0mg·L^-1时的细胞微核率为13.85‰,对照组的微核率为4.53‰,此时污染影响指数(PI)为3.06;当环境中存在表面活性剂LAS1.0mg·L^-1或pH值降到4.5和3.5时,同一Cd²⁺浓度下,蚕豆根尖细胞微核率、PI降低,同时伴有核变形,细胞中颗粒物增多,胚根组织不容易分散等症状,根的生长受到抑制,说明表面活性剂、酸雨对Cd²⁺的毒性有协同作用.pH3.5的酸雨环境中Cd²⁺对蚕豆细胞的损伤程度比pH4.5酸雨环境高.在检测高浓度、强毒性污染物的致突变效应时,应作至少3个稀释倍数,找出蚕豆根尖细胞最高微核率及PI.