Tolerance to paraquat-mediated oxidative and environmental stresses in squash (Cucurbita spp.) leaves of various ages

Paraquat is labeled for row-middle application on cucurbits, but drift to crop foliage is inevitable. Experiments were conducted to determine whether differential tolerance to paraquat existed among leaves of various ages in Cucurbita spp. (squash) and other plants, and to examine whether leaves tolerant to paraquat are also tolerant to other herbicides and abiotic stresses. Physiological responses to paraquat, including antioxidant activity, were investigated in squash leaves to identify mechanisms of paraquat tolerance. Although the level of paraquat tolerance differed by leaf age, cultivar, and species, the level of paraquat injury was lower in younger leaves than in older leaves in 14 of 18 squash cultivars and 5 of 12 other species tested. Cellular leakage and lipid peroxidation were consistently lower in the youngest leaf (leaf 4) than in the older leaves. Quantum yield and relative chlorophyll content were the same in all leaves of nontreated plants. Epicuticular wax content was higher in the youngest leaf than in leaves 1, 2, and 3 of cv. ‘Joongangaehobak’ and ‘Wonbiaehobak’. However, leaf cuticle content was not consistent with leaf ages. Differential leaf response to paraquat was partially correlated with the change in catalase, peroxidase, ascorbate peroxidase (APX), and glutathione reductase activities in nontreated and treated leaves. The APX activity in the youngest leaf was generally 2 times higher than in leaves 1-3 in both nontreated and treated plants. Ascorbate antioxidant levels were also higher in the youngest leaf than those in leaves 1-3. Leaves tolerant to paraquat were also tolerant to diquat and to abiotic stresses, low temperature and drought. However, tolerance to oxyfluorfen, which has a different mode of action than paraquat and diquat, was higher in older than in younger leaves. Higher tolerance to paraquat-mediated oxidative and abiotic stresses in young leaves of most squash cultivars might contribute to the differential prevention of oxidative damage in leaves of various ages.     

聚乙二醇胁迫对甘蔗生长前期叶片水势及脯氨酸代谢的影响

以3个甘蔗品种‘桂糖119’(‘GT119’)、‘新台糖16号’(‘ROC16’)、‘新台糖22号’(‘ROC22’)为材料,利用PEG6000淋灌于甘蔗幼苗根部模拟土壤水分胁迫,研究其对植株叶片水势、脯氨酸含量、P5CS、δ-OAT、ProDH酶活性等的影响。结果表明,3个品种经胁迫处理,其叶片水势都较对照有所下降;对于游离脯氨酸含量的变化,‘ROC16’在处理后第1天含量就明显上升,‘GT119’在处理2 d后也开始上升,而‘ROC22’在处理后12 d内其含量仍增加不明显;吡咯啉-5-羧酸合成酶活性经胁迫处理都较未处理表现活跃,‘GT119’与‘ROC16’在胁迫处理后酶活性表现上升趋势,而‘ROC22’变化不明显;鸟氨酸转氨酶活性变化不明显;脯氨酸脱氢酶活性,‘GT119’与‘ROC16’在处理1 d后稍有上升但在7天后都有下降,而‘ROC22’在第7天酶活性就开始提高。     

聚乙二醇胁迫对甘蔗生长前期叶片水势及脯氨酸代谢的影响

以3个甘蔗品种'桂糖119'('GT119')、'新台糖16号'('ROC16')、'新台糖22号'( 'ROC22')为材料,利用PEG6000淋灌于甘蔗幼苗根部模拟土壤水分胁迫,研究其对植株叶片水势、脯氨酸含量、P5CS、洫、ProDH酶活性等的影响.结果表明,3个品种经胁迫处理,其叶片水势都较对照有所下降;对于游离脯氨酸含量的变化,'ROC16'在处理后第1天含量就明显上升,'GT119'在处理2 d后也开始上升,而'ROC22'在处理后12 d内其含量仍增加不明显;吡咯啉-5-羧酸合成酶活性经胁迫处理都较未处理表现活跃,'GT1 19'与'ROC16'在胁迫处理后酶活性表现上升趋势,而'ROC22'变化不明显;鸟氨酸转氨酶活性变化不明显;脯氨酸脱氢酶活性,'GT119'与'ROC16'在处理1 d后稍有上升但在7天后都有下降,而'ROC22'在第7天酶活性就开始提高.     

Reactive oxygen intermediates and oxalic acid in the pathogenesis of the necrotrophic fungus Sclerotinia sclerotiorum

An effective colonization of the host plant tissue by the necrotrophic fungus Sclerotinia sclerotiorum requires the secretion of the non-host specific toxin oxalic acid (OA), which is known to suppress the generation of reactive oxygen intermediates (ROI). A full-length cDNA coding for an oxalate decarboxylase (TOXDC), which converts OA into CO₂ and formate, was isolated from the basidiomycete Trametes versicolor. It was overexpressed in tobacco plants to study the role of ROI and OA in the interaction between tobacco and S. sclerotiorum. The transgenic plants contained less OA and showed a delayed colonization of S. sclerotiorum; furthermore a strong ROI accumulation and nearly no catalase activity compared to the wild type (WT) plants could be detected. In addition, inoculation experiments with transgenic catalase-deficient plants (CAT1AS) and in vitro studies showed that S. sclerotiorum copes with strong ROI stress. Our results indicate that OA supports the infection process caused by S. sclerotiorum and the fungus itself is able to tolerate high ROI concentrations. The nucleotide sequence data is available from the NCBI Genbank nucleotide-sequence database under the number AY370675     

Effects of gender and temperature on oxidative stress enzymes in Nile tilapia Oreochromis niloticus exposed to paraquat

Many classes of environmental pollutants can enhance the intracellular formation of reactive oxygen species, which can conduce to the damage of macromolecules and changes in oxidant defences levels in fish. In the present study it was analysed the hepatic levels of superoxide dismutase (SOD), glutathione reductase (GR), and glutathione S-transferase (GST) in males and females of Nile tilapia Oreochromis niloticus exposed to paraquat (PQ), at 17 and 27 °C. Tilapia were exposed to a sublethal concentration of PQ (0.5 mg L⁻¹) during 45 days. Condition factor and hepatosomatic index of males and females exposed to PQ were significantly higher when compared with the control group, except in females at 17 °C. SOD and GST activities were higher in males and females exposed to PQ than in the control group at 17 and 27 °C. The levels of both enzyme activities revealed that they are sex-dependent with males exposed to PQ showing higher SOD activity (5.05 ± 0.13 and 4.84 ± 0.23 U/g protein, respectively at 17 and 27 °C) than females (4.21 ± 0.07 and 3.87 ± 0.27 U/g protein, respectively at the same temperature). Similar results were observed in GST activity. A GR activity significantly higher (9.09 ± 0.44 and 7.97 ± 1.08 U/g protein at 17 and 27 °C, respectively) was observed in PQ-exposed females, but not in exposed males. Fish exposed to PQ showed higher values of SOD and GST activities than the control group at both temperatures. These results are gender-dependent, while GR activity was higher only in PQ-exposed females. No significant differences were found for SOD, GST and GR activities between fish exposed to 17 and 27 °C, although males and females showed higher values at 17 °C. In short, this work advanced new knowledge on influence of gender in same biochemical parameters in tilapia exposed to PQ and demonstrated that their effects could be observed at different temperatures.     

Enhanced extracellular laccase activity as a part of the response system of white rot fungi: Trametes versicolor and Abortiporus biennis to paraquat-caused oxidative stress conditions

Effects of paraquat dichloride (PQ) on the laccase (LAC) activity and some biochemical parameters of Trametes versicolor and Abortiporus biennis strains belonging to white rot Basidiomycetes fungi were examined. PQ water solution was added to 10-day-old stationary cultures cultivated on a liquid medium. Having measured the activity of extracellular laccase during the first 120 h, we found that the addition of 25 μM paraquat to T. versicolor and 20 μM paraquat to A. biennis cultures significantly stimulated the LAC activity in comparison to the control value (without PQ). Native PAGE gel analysis demonstrated that no new isoforms of laccase appeared in the presence of PQ stress. The increase of LAC activity was connected with dry weight loss. Enhanced activity of extracellular superoxide dismutase was observed during the first 48 h after PQ application in both investigated strains. The PQ-treatment also caused an evident increase of catalase activity, formaldehyde level and depletion of glutathione in T. versicolor as well as in A. biennis mycelia.     

干旱胁迫下3个油菜品种地上、地下部生长特征与抗旱性的关系

为了探索干旱胁迫下不同抗旱性油菜品种的地上、地下部生长特征与抗旱性的关系,通过土柱栽培试验,对油菜品种DR1、DR2和DR3在不同水分处理条件下不同土层根量、地上部生物量、冠层覆盖面积及抗旱性之间的关系进行研究。结果表明：3个品种在水分胁迫和正常供水条件下产量和根系生物量在品种间均达到显著性差异,3个品种的抗旱能力大小依次为：DR1>DR3>DR2;不同水分处理下油菜的根系主要分布于0~30 cm土层,占根系总量的70%以上;在干旱胁迫下,3个品种DR1、DR2和DR3的总根量分别减少了22.53%、24.17%和24.53%,但仍表现出抗旱性强的品种DR1的根系总量最大,达到12.07 g,其次为品种DR3和DR2;在大于30cm的土层中,DR1的根系量占到总根量的31.5%,这表明根系垂直分布量的多少对抗旱性的影响较大,同时植株冠层面积、总生物量、根系干重与抗旱性的直接通径系数分别为0.5861、0.4514、0.5715,说明除了根系外,大的冠层面积可减少地表蒸发有利于作物抗旱。     

Subacute chlorpyrifos-induced oxidative stress in rat erythrocytes and the protective effects of catechin and quercetin

This study examined the effects of chlorpyrifos in the rat erythrocyte antioxidant system and evaluated the ameliorating effects of catechin and quercetin on the oxidative damage induced by chlorpyrifos. Sexually mature male Wistar rats were given chlorpyrifos (5.4 mg/kg, 1/25 of the oral LD₅₀), catechin (20 mg/kg), quercetin (20 mg/kg), catechin plus chlorpyrifos, and quercetin plus chlorpyrifos daily via gavage for four weeks. No statistical differences were found in the catechin-only and quercetin-only groups compared with the control group. By the end of the fourth week, chlorpyrifos alone increased the levels of malondialdehyde (MDA) and decreased superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities compared with the control group in rat erythrocytes. In the catechin-plus-chlorpyrifos and quercetin-plus-chlorpyrifos groups, there were statistically significantly decreased MDA levels and increased SOD, CAT, and GPx activities compared with the chlorpyrifos-only group. Thus, it appears that catechin and quercetin ameliorate chlorpyrifos-induced oxidative stress in rat erythrocytes in vivo.     

NaCl胁迫下萝卜幼苗根系生理和细胞核形态的变化

以萝卜幼苗为材料,研究了0.15 mol/L NaCl胁迫处理不同时间其根系的生长速度、活力、过氧化物酶(POD)活性和相对电导率的变化,并观察了根尖细胞核形态的变化.结果表明,随着NaCl胁迫时间的延长,萝卜幼苗根系生长速度减慢,根系活力降低,胁迫时间超过48 h时,二者均迅速下降,表现得更为明显;萝卜幼苗根系POD活性和相对电导率则不断增大,胁迫48 h时达到最大,之后POD活性迅速降低,相对电导率随之降低;根尖细胞核由原来规则的圆形转变为各种不规则形状,出现不同程度的凋亡特征.     

低温胁迫下白菜型冬油菜脂肪酸组分及FAD3的差异表达分析

为探究白菜型冬油菜(Brassica rapa L.)脂肪酸组分对低温胁迫的响应及脂肪酸去饱和酶FAD3(ω-3-fatty acid desaturase)基因与抗寒性的关系,采用气相色谱-质谱法测定了3个不同抗寒性白菜型冬油菜品种在低温胁迫下根和叶的脂肪酸组分变化;利用同源克隆法获得白菜型油菜陇油7号FAD3的CDS序列,利用生物信息学方法对其进行分析。结果显示:低温胁迫下,强抗寒品种陇油7号根部亚油酸和亚麻酸的含量较不抗寒品种Lenox分别高157%和89%,陇油7号根部脂肪酸不饱和指数(IUFA)较Lenox高91%,即低温胁迫下,强抗寒品种的亚油酸、亚麻酸和IUFA均显著高于不抗寒品种;陇油7号FAD3序列CDS区全长1 290 bp,编码429 aa,分子质量约49.16 kD,等电点为8.60,是一种稳定的亲水蛋白。多序列比对分析发现其编码蛋白与同一科属中大白菜相似性最高,为100%,进化树分析结果也表明FAD3蛋白与大白菜亲缘关系较近。荧光定量表达分析发现低温胁迫下,FAD3基因在陇油7号、天油2号和Lenox根中的表达量较对照(22℃)分别增加了690%、590%和710%,说明FAD3基因通过上调表达来适应低温,且其表达量与IUFA呈正相关关系。     

螺虫乙酯对雌性斑马鱼的毒性及氧化应激效应

为评价新型季酮酸衍生物类杀虫剂螺虫乙酯(spirotetramat)对水生生物的毒性,以雌性斑马鱼为受试对象,研究了螺虫乙酯对其的急性毒性及氧化应激效应。急性毒性试验测得螺虫乙酯对雌性斑马鱼的96 h-LC50值为7.21 mg/L,属中等毒性。经不同浓度螺虫乙酯(0、36、360和1 800μg/L)处理28 d后,通过检测铜/锌超氧化物歧化酶(Cu/Zn-SOD)、锰超氧化物歧化酶(Mn-SOD)、过氧化氢酶(CAT)和谷胱甘肽过氧化物酶(GSH-Px)等抗氧化酶的活性,Cat、Gpx、Mn-Sod、Cu/Zn-Sod等基因的相对表达量,以及丙二醛(MDA)含量等指标的变化水平,研究了螺虫乙酯对斑马鱼肌肉组织的氧化应激效应。结果表明,螺虫乙酯可引起斑马鱼肌肉组织中CAT、GSH-Px活性和MDA含量,以及Cat、Mn-Sod、Gpx的相对表达量显著升高,但未发现螺虫乙酯对Cu/Zn-SOD活性及Cu/Zn-Sod的相对表达量有明显影响。研究表明,螺虫乙酯能够诱导雌性斑马鱼肌肉组织的氧化应激效应,并可能引起机体的氧化损伤。     

Evaluation of aspect of some oxidative stress parameters using vitamin E, proanthocyanidin and N-acetylcysteine against exposure to cyfluthrin in mice

A hundred and sixty female white mice, each weighing 35-40 g, were used in this study. The animals were assigned into eight groups as one control group and 7 experimental groups. Groups 2, 3 and 4 were administered N-acetylcysteine (NAC), proanthocyanidin and vitamin E alone, at doses of 100 mg/kg/body weight/day by intra-peritoneal, oral route and, intramuscular, respectively. Group 5 was administered a single dose of cyfluthrin (100 mg g/kg/body weight ∼1/3LD₅₀) by oral, whereas Groups 6, 7 and 8 were given cyfluthrin+NAC, cyfluthrin+proanthocyanidin and cyfluthrin+vitamin E, at the same dose, respectively. The administration of the drugs was initiated following the administration of cyfluthrin, and continued until the end of the seventh day of the study. Blood samples were collected from each group, 24 h, and 3, 7 and 9 days after the administration of cyfluthrin for the assessment of blood malondialdehyde (MDA) levels and superoxide dismutase (SOD) and catalase (CAT) activities. According to the data obtained, compared to the control group, increase in the plasma MDA level of the group administered cyfluthrin alone, and decrease in erythrocyte SOD activities in some periods and CAT activities in all periods were determined. On the other hand, especially, MDA levels and CAT activities were observed to move closer to values of the control group, in the groups that were administered NAC, proanthocyanidin and vitamin E in addition to cyfluthrin. In other words, in most periods, decrease in plasma MDA levels, and increase in erythrocyte CAT and SOD activities were observed in comparison to the group administered cyfluthrin alone. Statistical analyses demonstrated significant differences to exist between the groups on the third, seventh and ninth days with respect to plasma MDA levels, and the third and ninth days with respect to erythrocyte SOD and CAT activities (P < 0.05). However no significant difference was demonstrated in any of the periods in the groups that were administered NAC, proanthocyanidin and vitamin E alone in comparison to the control group (P > 0.05). In view of the parameters examined, animals were concluded to be affected by cyfluthrin and the administration of the three compounds at the indicated doses and for the indicated periods were considered to alleviate the adverse effects of cyfluthrin partly throughout the study period.     

低温胁迫下甘蓝型冬油菜BnYUCCA8基因差异表达及内源生长素含量变化

甘蓝型冬油菜下胚轴长短与其抗寒性强弱呈负相关关系。为研究下胚轴伸长相关的BnYUCCA8基因对低温胁迫的响应,采用同源克隆技术从甘蓝型冬油菜中克隆了BnYUCCA8基因,其CDS全长1 281 bp,编码426个氨基酸。生物信息学分析表明,BnYUCCA8蛋白是一个不稳定的疏水性蛋白,与埃塞俄比亚芥和甘蓝中YUCCA8蛋白的亲缘关系最近。荧光定量PCR结果表明,BnYUCCA8在叶和根中表达量最高,花和角果中表达量相对较低,且苗期表达量高于花期。随低温胁迫加剧,BnYUCCA8表达量总体呈降低趋势,且‘天油2288’(下胚轴伸长较长的弱抗寒品种)较‘16VHNTS158’(下胚轴伸长较短的强抗寒品种)基因表达量高。内源IAA含量的测定结果表明,在低温处理24 h时,‘16VHNTS158’中IAA含量在4℃、0℃、-4℃较常温(22℃)分别降低68%、92%、97%,‘天油2288’中分别降低了77%、89%、94%,且‘16VHNTS158’较‘天油2288’IAA含量在常温、4℃、0℃、-4℃分别低19%、14%、40%、39%。对BnYUCCA8相对表达量、内源IAA含量和下胚轴...     

Protective effects of Nigella sativa oil on propoxur-induced toxicity and oxidative stress in rat brain regions

Propoxur (PPr) is a widely used broad spectrum carbamate insecticide mainly used to control household pests. Because of the widespread use of pesticides for domestic and industrial applications, evaluation of their neurotoxic effects is of major concern to public health. The aim of the present study was to evaluate the possible protective effects of Nigella sativa oil (NSO), an antioxidant agent, against PPr-induced toxicity and oxidative stress in different brain regions of rats including cerebellum, cortex and hippocampus. In the present study, 32 male Sprague-Dawley rats were used and divided into four equal groups. Group 1 was allocated as the control group. Groups 2-4 were orally administered 1 ml/kg/bw/day NSO, 8.51 mg/kg/bw/day PPr or NSO plus PPr, respectively, for 30 days. Lipid peroxidation (LPO), protein carbonyl content (PCC) and acetylcholine esterase activity (AChE) were determined. Enzymatic antioxidant activities [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione-S-transferase (GST)] and non-enzymatic antioxidants [reduced glutathione (GSH)] were determined. PPr treatment significantly increased the levels of LPO, PCC and oxidized glutathione (GSSG) in brain regions. On the contrary, levels of GSH and the activities of SOD, CAT, GSH-Px, GST and AChE were significantly decreased. NSO treatment to PPr intoxicated rats restored such biochemical parameters to within control levels except GST activity, emphasizing its antioxidant role. We conclude that NSO significantly reduces PPr-induced toxicity and oxidative stress in rat brain regions via a free radicals scavenging mechanism.     

Glycosylation and oxidative dimerization of resveratrol are respectively associated to sensitivity and resistance of grapevine cultivars to downy mildew

Levels of resistance to Plasmopara viticola, from susceptible to highly resistant, of different grapevine cultivars were observed in vineyards and confirmed by the symptoms developed after inoculations. On the abaxial surface of infected leaves, P. viticola developed abundant sporangiophores on susceptible cultivars (Chasselas, Gamay, Gamaret and Pinot Noir), whereas on less susceptible cultivars (Seyval Blanc and Johanniter) the parasite produced few sporangiophores and some necrotic spots at the site of infection. On resistant cultivars (Bronner, Solaris, IRAC 2091), P. viticola induced a hypersensitive response and only necrotic spots were visible and the disease ceased to develop. Stilbenes were analyzed 4, 7, 24, 48 h post-infection (hpi) on small leaf samples cut from the site of infection. Large differences were observed between the cultivars at 24 and 48 hpi. Susceptible grapevines produced resveratrol and its glycoside, piceide. In contrast, resistant plants produced high concentration of ε- and δ-viniferin. Resveratrol and piceide have little or no toxicity activity against P. viticola, whereas δ-viniferin is highly toxic and can be considered an important marker for resistance of grapevine to downy mildew. The importance of oxidative dimerization of resveratrol in comparison to the extent of its glycosylation in defense reaction of grapevines against P. viticola is discussed.     

马铃薯丝氨酸羧肽酶类蛋白StSCPL家族的鉴定及干旱胁迫响应分析

在全基因组水平上鉴定了马铃薯SCPL基因家族,并对其成员的基本特征、蛋白质保守结构域、进化关系和干旱胁迫下的表达模式进行了分析。同时,以干旱耐受性不同的马铃薯品种‘陇薯10号’(干旱耐受型)和‘大西洋’(干旱敏感型)为试验材料,利用高通量测序分析了干旱胁迫关键差异表达基因StSCPLs。结果表明,马铃薯中共鉴定到了41个StSCPLs,不对称分布在11条染色体中,多数成员含有多个内含子。其蛋白均含有1个细胞内分泌和转运的信号肽、底物结合位点、N-糖基化位点以及与催化作用相关的进化保守基序。在非生物胁迫下,大多数StSCPLs都具有多胁迫响应性。在干旱耐受性不同的马铃薯品种中,StSCPLs表现出差异表达特性。同时,LncRNA及其靶StSCPL介导的调控网络显示,StSCPL3和StSCPL34分别是lncRNA MSTRG.2301.1和MSTRG.19548.1的靶基因,在干旱耐受性不同的品种中显著差异表达,可能是马铃薯对干旱胁迫响应的潜在靶点。     

外源H2O2对干旱胁迫下裸燕麦 幼苗叶片生理特性的影响

为探讨信号分子过氧化氢(H₂O₂)对干旱胁迫下裸燕麦生理响应的调控机制,以砂培白燕7号幼苗为材料,研究了喷施0.01 mmol·L^-1 H₂O₂对17.8%聚乙二醇6000模拟的干旱胁迫下叶片光合特性、活性氧代谢、渗透调节物质积累和幼苗生长的影响。结果表明：喷施H₂O₂后,干旱胁迫下的裸燕麦幼苗叶片叶绿素a、叶绿素b、总叶绿素、类胡萝卜素含量和叶绿素a/b较对照(喷H₂O后干旱胁迫)分别提高了20.0%、12.9%、18.5%、8.1%和24.3%,叶片净光合速率、气孔导度、胞间CO₂浓度和水分利用效率分别提高了20.6%、25.9%、12.0%和33.8%,蒸腾速率降低了9.7%;喷施H₂O₂还使干旱胁迫下裸燕麦幼苗叶片的过氧化氢酶、抗坏血酸过氧化物酶活性和抗坏血酸含量分别提高了113.5%、102.9%和13.8%,而超氧化物歧化酶、过氧化物酶活性及O^{—[KG-1][JX*3]·[JX-*3]}₂、H₂O₂、丙二醛含量和细胞膜相对透性分别下降了21.5%、60.4%、29.3%、38.4%、19.7%和14.2%,可溶性蛋白质、可溶性糖、游离氨基酸和脯氨酸含量分别上升了10.5%、40.3%、13.8%和17.2%,幼苗株高、根长、植株鲜重、植株干重和相对含水量分别提高了14.8%、25.0%、20.1%、11.0%和5.93 %,但谷胱甘肽含量没有显著变化。表明外源H₂O₂能够通过降低膜脂过氧化程度和促进渗透溶质积累,改善叶片光合功能和植株水分状况,从而减轻干旱对裸燕麦幼苗生长的抑制,增强裸燕麦的抗旱性。     

Oxidative stress induces high transcription of Rhm52 and Rhm54, novel genes identified as being involved in recombinational repair in Magnaporthe grisea

The first two recombinational repair genes of Magnaporthe grisea were cloned. Analysis of the deduced amino acid sequences revealed that Rhm52 and Rhm54 are Saccharomyces cerevisiae RAD52 and RAD54 homologs, respectively. Phenotypic complementation testing of these genes showed their function in recombinational repair. Both genes were in single copies in M. grisea genome. Expression of these genes was induced by methyl methanesulfonate and ultraviolet radiation as known for other homologs of the RAD52 epistasis group. Higher induction of both genes by oxidative stress and heat shock indicated the probability for recombinational repair during the infection cycle of M. grisea. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession numbers AB091332 and AB091330