荧光增白剂对伊朗核型多角体病毒分离株对棉铃虫幼虫的杀虫活性的增效作用（英文）

在室内条件下调查了几种荧光增白剂对采自伊朗East Azarbaijan的棉铃虫Helicoverpa armigera核型多角体病毒两个地域株(EAZ-I 和EAZ-II)对棉铃虫2龄幼虫的杀虫活性, 以提高这两个地域株的生物学活性。结果表明：与EAZ-II相比, EAZ-I的杀虫活性强,其对棉铃虫幼虫的LC₅₀和 LT₅₀ 值低（分别为1.98×103 OB/mL和122.7 h）。本研究所用的所有荧光增白剂均能有效增强病毒的生物学活性,特别是0.2% 的Tinopal F-3543与EAZ-I 混用对棉铃虫幼虫的LC50值最低(5.16×102 OB/mL),与病毒单独应用相比活性增强了3.84倍。幼虫致死的相对速率测定结果表明,荧光增白剂提高了菌株的LT₅₀值,其中Tinopal F-3543 的效果最佳。这些结果说明,在害虫综合治理中影响围食膜通透性的荧光增白剂与核型多角体病毒制剂混用是一种可供选择的重要方法。     

Infection of Anastrepha ludens (Diptera: Tephritidae) larvae by Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae) under laboratory and field conditions

Laboratory and field experiments were performed to determine the efficiency of the entomopathogenic nematode Heterorhabditis bacteriophora against third instar larvae of the tephritid fruit fly Anastrepha ludens. Infection was affected by low (6%) and high (12-24%) soil moisture; the highest prevalence of infection was observed at 9% moisture. LC₅₀ values were estimated under laboratory conditions at densities of 0.16, 0.26 and 0.64 larvae/cm³ of sand in containers of different depths (2, 5 and 8 cm) at 10% moisture, and larval ages (third instar, early versus late stadium). Third instar A. ludens were significantly more susceptible to infection early in the stadium than late in the stadium, irrespective of host density (LC₅₀ ∼15 infective juvenile nematodes/cm² soil surface). Infection of late stadium third instars was significantly reduced at low density. Application of 115 and 345 infective juvenile nematodes/cm² (representing one and three times the laboratory LC₅₀ at the lowest host density, respectively), in experimental plots in a commercial mango orchard, resulted in 46.7% (range of SE: 45.2-48.1) and 76.1% (SE: 74.8-77.3) infection, respectively. We conclude that H. bacteriophora merits further study as a natural enemy of Anastrepha spp. in tropical regions of the Americas.     

氰氟虫腙对草地贪夜蛾的毒力与田间防效

【目的】本研究旨在明确氰氟虫腙对草地贪夜蛾Spodoptera frugiperda幼虫的毒力水平和田间防治效果,为科学使用氰氟虫腙防治草地贪夜蛾提供参考依据。【方法】采用饲料混毒法在室内测定了氰氟虫腙与4种常用杀虫剂甲维盐、氯虫苯甲酰胺、虱螨脲和茚虫威对草地贪夜蛾3和6龄幼虫的致死中浓度(LC₅₀)及LC₉₀值,以及LC₉₀浓度的这些杀虫剂对3龄幼虫的致死中时(medium lethal time, LT₅₀)值。采用人工喷雾方法测定了玉米田中22%氰氟虫腙悬浮剂(6.6 g/667 m²)、22%氰氟虫腙悬浮剂(17.6 g/667 m²)、5.7%甲维盐水分散剂(1 g/667 m²)和150 g/L茚虫威悬浮剂(2 g/667 m²)对草地贪夜蛾幼虫的防效。【结果】室内生测结果显示,供试的5种杀虫剂中氰氟虫腙对草地贪夜蛾3和6龄幼虫均具有较高的毒力,其LC₅₀值分别为2.64和4.3...     

Infectivity and ecology of Pseudomonas spp. from natural epizootics in the rice leaf folder, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) in India

In 2001, populations of the leaf folder (LF) (Cnaphalocrocis medinalis Guenee) reached 19-30 larvae/hill in Rabi rice (variety Lalat) fields at Choudwar, Baranga, Alani and Tangi, Orissa, India infesting 61-98% of the plants. Three bacteria viz. Pseudomonas aeruginosa (Pa1 and Pa2) and P. fluorescens (Pf) infected 62-98% of the larvae in different fields. No correlation was found among populations of the Pseudomonas spp. on the rice phyllosphere and larvae harboring the bacteria at different fields. The median lethal concentrations (LC₅₀s; ×10³ bacteria/mL) of Pa1, Pa2 and Pf were 4-4.2, 4.8-4.9 and 5.7-5.9, respectively, for the leaf piece assay and 4.8-4.9, 5-5.1 and 6.3-6.7, respectively, for the potted plant assay against second to fifth instar larvae. The median lethal times (LT₅₀s) were 2.1-2.4, 3.2-3.5 and 5.3-6 days for the leaf piece assay, and 4-4.7, 4.7-4.9 and 6.1-6.8 days for the potted plant assay with Pa1, Pa2 and Pf, respectively. The Pa1 and Pa2 were compatible, exhibited synergistic effect and co-inoculation reduced the LC₅₀ and LT₅₀ as compared to inoculation with individual organisms. The Pf had no synergism with Pa1 or Pa2, and therefore, the lethal values for Pf alone or with the other bacteria were similar. Fulfillment of Koch's postulates confirmed that Pa1, Pa2 and Pf were pathogens of C. medinalis.     

Virulence of entomopathogenic nematodes (Rhabditida: Steinernematidae, Heterorhabditidae) against Tipula paludosa (Diptera: Tipulidae), a turfgrass pest on golf courses

The European crane fly (ECF), Tipula paludosa Meigen feeds on leaves, crowns, and roots of cool-season turfgrasses causing damage to residential lawns and golf courses. A laboratory study was conducted to determine the susceptibility of ECF larvae to four commercial entomopathogenic nematode (EPN) species (Heterorhabditis marelatus, H. megidis, Steinernema carpocapsae and S. feltiae). The virulence of four S. feltiae isolates recovered from golf courses in Quebec and Ontario were also compared to a commercial strain. LC₅₀ values of EPN against late instar ECF larvae were 152, 562, 763, and 3584 for S. feltiae, H. megidis, H. marelatus and S. carpocapsae, respectively. When non-feeding (without grass seedling), ECF larvae mortalities decreased for all nematode species and concentrations tested. At 25°C, LC₅₀ values for the two most virulent indigenous S. feltiae were 129 and 187 nematodes/larva, not different from the commercial strain. At 5°C, the commercial S. feltiae was more effective than both BIC14A and RE6A isolates against ECF larvae. However, at 15°C, BIC14A was the most virulent at the low concentration of 200 IJs/larva.     

Determination of the maximum and minimum lethal temperatures (LT50) for Loxosceles intermedia Mello-Leitão, 1934 and L. laeta (Nicolet, 1849) (Araneae, Sicariidae)

In this study, the maximum and minimum lethal temperatures (LT₅₀) of L. intermedia and L. laeta were determined in two treatments: gradual heating (25–50°C) and cooling (25°C to −5°C), and 1 h at a constant temperature. In gradual temperatures change, L. intermedia mortality started at 40°C and the LT₅₀ was 42°C; for L. laeta, mortality began at 35°C and the LT₅₀ was 40°C. At low temperatures, mortality was registered only at −5°C for both species. In the constant temperature L. intermedia showed a maximum LT₅₀ at 35°C and L. laeta at 32°C; the minimum LT for both species was −7°C.     

Fluorescent brightener inhibits apoptosis in baculovirus-infected gypsy moth larval midgut cells in vitro

Fluorescent brighteners significantly lower the LC₅₀ and LT₅₀ in a variety of nucleopolyhedrovirus-insect host systems. In larvae of the gypsy moth, Lymantria dispar (L.), a European NPV strain of virus (LdMNPV) does not normally replicate in the midgut, but addition of a fluorescent brightener (Calcofluor M2R) to the virus suspension results in productive infections. In the current study, we show that LdMNPV also does not replicate in a larval midgut primary cell culture system unless a fluorescent brightener (Blankophor P167) is added. Morphological and cellular changes characteristic of apoptotic cell death were noted in infected midgut cells in vitro. We used the TUNEL assay to measure apoptosis in virus-challenged midgut cell cultures at 24-48 h post-inoculation. A significant decrease in apoptotic midgut cells was noted in the presence of 0.01 M brightener. The inhibition of apoptosis and presumptive inhibition of shedding of infected midgut cells in the presence of fluorescent brightener in the insect midgut appeared to promote virus replication and are likely to be partly responsible for enhancement of LdMNPV activity that is observed in gypsy moth larvae.     

绿僵菌MaFZ-13对橙带蓝尺蛾幼虫致病力及林间防治效果

【目的】橙带蓝尺蛾Milionia basalis近年来在我国南方地区严重危害罗汉松Podocarpusmacrophyllus和竹柏Podocarpus nagi,扩散蔓延速度快,造成了很大的损失。本研究旨在评估金龟子绿僵菌Metarhizium anisopliae MaFZ-13菌株对橙带蓝尺蛾幼虫的致病力,探寻橙带蓝尺蛾生物防治新资源。【方法】通过绿僵菌MaFZ-13不同浓度(1.0×10⁵~1.0×10⁹孢子/mL)孢子悬浮液接种橙带蓝尺蛾幼虫,运用时间-剂量-死亡率(TDM)模型对生物测定结果进行分析,同时通过林间喷施1.0×10⁸孢子/mL绿僵菌孢子悬浮液进行林间防治效果试验。【结果】橙带蓝尺蛾幼虫累计死亡率随着绿僵菌MaFZ-13孢子悬浮液孢子浓度的增加和接种时间的延长而增大。接种1.0×10⁹孢子/mL孢子悬浮液8 d后以及接种1.0×10⁸孢子/mL孢子悬浮液10 d后,幼虫死亡率均达到100%;接种1.0×10⁷孢子/mL孢子悬浮液15 d后幼虫死亡率为95.6%。应用TDM模型对生测数据进行分析,结果表明所建模型通过Hosmer-Lemeshow拟合异质性检验,并由模型估算出了该菌株对橙带蓝尺蛾幼虫的致死剂量和致死时间。绿僵菌MaFZ-13菌株接种4, 5, 6和7 d后的半致死剂量(LC₅₀)对数估计值分别为7.99, 7.12, 6.46和5.83。以1.0×10⁷, 1.0×10⁸和1.0×10⁹孢子/mL的孢子浓度接种时,绿僵菌MaFZ-13菌株对橙带蓝尺蛾幼虫的LT₅₀值分别为5.19,3.99和2.81 d。林间用1.0×10⁸孢子/mL绿僵菌孢子悬浮液喷洒9 d后橙带蓝尺蛾幼虫死亡率可达到85.8%,防治效果为85.05%。【结论】绿僵菌MaFZ-13对橙带蓝尺蛾幼虫具有较强的致病力,林间防治效果良好,具有较好的应用潜力。     

Efficacy of the Entomopathogenic Fungus, Culicinomyces clavisporus against Larvae of the Biting Midge, Culicoides nubeculosus (Diptera: Ceratopogonidae)

Culicinomyces clavisporus, a fungal pathogen of a wide range of mosquito species, was investigated in relation to potential pathogenicity against Culicoides nubeculosus biting midge larvae. Seven different C. clavisporus strains were assayed. Each showed some degree of activity against C. nubeculosus larvae with LC₅₀ values of between 3.2×10^-5 and 1.1×10^-6 spores/mL; these effects occurred in dose-dependent manners and tended to be delayed until 72-96 h post treatment. The results are discussed in relation to incorporation of C. clavisporus into biocontrol programmes for Culicoides spp.     

对桃蚜高毒力的蜡蚧菌菌株筛选

【目的】桃蚜Myzus persicae是一种世界性的重要农作物害虫,近年来已对多种化学杀虫剂产生抗性。本研究旨在筛选对桃蚜具有高毒力且培养性状优良的蜡蚧菌菌株。【方法】选用蜡蚧菌属Lecanicillium 2个种的7个菌株,即刀孢蜡蚧菌L.psalliotae 3个菌株(HFLP006, HFLP021和HFLP025)和渐狭蜡蚧菌L.attenuatum 4个菌株(HFLA032, HFLA041, HFLA064和HFLA066),接种在SDAY平板上培养并观察菌落生长与产孢性状;以2.0×10⁷孢子/mL悬浮液用浸渍法测定对桃蚜无翅成蚜的致死率和致死中时(LT₅₀);进而用系列浓度(1.0×10⁴-1.0×10⁸孢子/mL) HFLP006和HFLA032菌株孢子悬浮液测定其对桃蚜无翅成蚜的致死中浓度(LC₅₀);利用体视显微镜逐日观察1.0×10⁸孢子/mL HFLP006菌株孢子悬浮液侵染后无翅成蚜的染病症状变化。【结果】在SDAY平板上7个...     

Hydrogen peroxide degradation by immobilized cells of alkaliphilic Bacillus halodurans

Whole cells of Bacillus halodurans LBK 261 were used as a source of catalase for degradation of hydrogen peroxide. The organism, B. halodurans grown at 55°C and pH 10, yielded a maximum catalase activity of 275 U g^-1 (wet wt.) cells. The catalase in the whole cells was active over a broad range of pH with a maximum at pH 8-9. The enzyme was optimally active at 55°C, but had low stability above 40°C. The whole cell biocatalyst exhibited a K_m of 6.6 mM for H₂O₂ and V_max of 707 mM H₂O₂ min^-1 g^-1 wet wt. cells, and showed saturation kinetics at 50 mM H₂O₂. The cells were entrapped in calcium alginate and used for H₂O₂ degradation at pH 9 in batch and continuous mode. In the batch process, the immobilized preparation containing 1.5 g (wet wt.) cells could be recycled at least four times for complete degradation of the peroxide in 50 mL solution at 25°C. An excess of immobilized biocatalyst could be used in a continuous stirred tank reactor for an average of 9 days at temperatures upto 55°C, and in a packed bed reactor (PBR) for 5 days before the beads started to deform.     

黑水虻幼虫的耐饥力及饥饿幼虫复食后的生物学特性

【目的】旨在明确黑水虻Hermetia illucens幼虫的耐饥力及饥饿幼虫复食后的发育、生殖力等生物学特性,为评估饥饿对黑水虻后续发育的影响并指导生产实践提供依据。【方法】将不同日龄或不同体重黑水虻幼虫进行不同时长的饥饿处理,测定和分析其耐饥力与日龄、百头重的关系;对7日龄幼虫进行不同时长的饥饿处理后再复喂,测定不同饥饿时长对其预蛹出现时间、总预蛹率、预蛹重、成虫繁殖等的影响。【结果】黑水虻幼虫饥饿后的半数致死时间(LT₅₀)与日龄成指数关系,与体重呈线性相关。7日龄幼虫的耐饥力较强,LT₅₀超过了50 d,饥饿30 d时存活率仍然达到了95%。百头重小于0.5 g的个体,其LT₅₀小于30 d;百头重在2～2.5 g的个体,其LT₅₀在45～70 d。幼虫超过8日龄时或百头重超过4.5 g时,多数个体在饥饿5 d时就提前进入了后续发育阶段。7日龄幼虫饥饿40 d内复食,其预蛹率未受到影响,但预蛹重显著增加;短期饥饿(0～10 d)对其成虫产卵量无显著影响,长期饥饿(30～40 d)使其成虫产卵量显著下降;饥饿长达30 d以上时,卵孵化率也显著降低。【结论】本研究明确了不同体重或不同日龄的黑水虻幼虫都具有一定的耐饥力;饥饿幼虫复食后预蛹重显著增加。     

乙基多杀菌素和印楝素对西花蓟马生长发育及繁殖的亚致死效应

为探讨乙基多杀菌素和印楝素对西花蓟马的亚致死效应,采用浸叶法确定了它们对西花蓟马2龄若虫的亚致死浓度(LC₂₅),并研究了该浓度下两种生物源农药对西花蓟马生长发育和繁殖力的影响.结果表明: 两种生物源农药亚致死浓度处理对西花蓟马均有不同程度的影响.在两性生殖方式下,乙基多杀菌素对西花蓟马产卵前期、雌成虫寿命和产卵量均无显著影响,但雄成虫寿命显著缩短;印楝素处理后,西花蓟马产卵量显著降低,产卵前期明显延长.在孤雌生殖方式下,不论乙基多杀菌素和印楝素处理,西花蓟马产卵前期均明显延长,但只有印楝素使雌成虫寿命缩短和产卵量显著降低.两种生物源农药对西花蓟马次代各虫态的发育历期影响不同,无论在何种生殖方式下,乙基多杀菌素处理后西花蓟马的未成熟期均明显短于印楝素处理.乙基多杀菌素处理后西花蓟马的内禀增长率(r_m)和周限增长率(λ)均高于对照,而印楝素较对照低.以上结果说明,两种杀虫剂对西花蓟马生长发育和繁殖影响不同,乙基多杀菌素亚致死浓度对西花蓟马种群的增长有一定的刺激作用,而印楝素有明显的抑制作用.两种杀虫剂的影响程度还与西花蓟马的生殖方式有关.     

Infectivity, speed of kill, and productivity of a baculovirus expressing the itch mite toxin txp-1 in second and fourth instar larvae of Trichoplusia ni

A cDNA clone of the gene coding for the paralytic neurotoxin (tox34) from the female straw itch mite, Pyemotes tritici, was created by RT-PCR and inserted into the genome of the Autographa californica nucleopolyhedrovirus (AcMNPV) under the control of the AcMNPV p10 promoter. This recombinant virus, AcTOX34.4, caused a rigid paralysis in infected larvae. The infectivity of AcTOX34.4 was compared to the wild-type parent strain, AcMNPV-C6, in second and fourth instar larvae of the cabbage looper, Trichoplusia ni. There were no significant differences in LD(50) values between the recombinant virus and its wild-type parent strain but, as expected, the LD(50) was lower for second instar larvae. The mean time to death and yield of occlusion bodies were measured in second and fourth instar T. ni larvae at a high (100% mortality) and low (<50% mortality) doses of the virus. The mean time to death of recombinant infected larvae was reduced by 50-60% compared to larvae infected with the wild-type strain, depending on virus dose and instar, with these larvae becoming paralysed after approximately 60 h and dying 10-20 h later. This is among the fastest speeds of kill recorded for recombinant baculoviruses. Fourth instar larvae were found to succumb to the recombinant virus more quickly than the second instar larvae. The increase in the speed of kill of the recombinant virus was accompanied by a large reduction of approximately 95% in the yield of progeny virus. The yield of virus showed a highly significant relationship with time to death, but this relationship was complex and varied between the different viruses, concentrations, and instars. The yield per unit weight of the larvae was found to be constant at a low virus dose and increased over time at a high virus dose, irrespective of instar and virus. It is predicted that these changes in the performance of the recombinant virus would act toward reducing its fitness, leading to it being outcompeted by the wild type in field situations.     

Infectivity of Steinernema spp. (Nematoda: Steinernematidae) to Adult Litter Beetles, Alphitobius diaperinus (Coleoptera: Tenebrionidae) in the Laboratory

Three species of Steinernema, S. carpocapsae, S. feltiae, and S. scapterisci consisting of 12 different strains, were tested for their infectivity towards adults of the litter beetle Alphitobius diaperinus. Of the five most promising nematode strains, LC₅₀ values ranged from 1.5 to 77.0 nematodes per host in the filter paper assays. Assays in poultry litter material revealed LC₅₀ values to be 5.8 and 14.6 nematodes per host for the Mexican S. carpocapsae strain and Pye S. feltiae strain.     

Germination, Radial Growth, and Sporulation of Beauveria bassiana and Metarhizium anisopliae Isolates and Their Virulence to Chilo partellus (Lepidoptera: Pyralidae) at Different Temperatures

The effect of temperature regimes on conidia germination, radial growth and virulence of Beauveriabassiana and Metarhizium anisopliae against the spotted stalk borer Chilo partellus was investigated with Ethiopian isolates. Conidia germination, radial growth and sporulation of all isolates were retarded at 15 and 35°C. A suitable temperature range for the isolates was between 20 to 30°C. Conidia germination was less tolerant of low temperature (15°C) than radial growth. Radial growth and sporulation reacted differently to temperature. At both 25 and 30°C, all isolates induced 100% mortality to C. partellus larvae in six days. The LT₅₀ decreased for the isolates with increasing temperature.     

Increased enantioselectivity in the enzymatic hydrolysis of amino acid esters in the ionic liquid 1-butyl-3-methyl-imidazolium tetrafluoroborate

The initial rate and enantioselectivity of enzymatic asymmetric hydrolysis of amino acid esters were examined in methylimidazolium-based ionic liquids with anions including tetrafluoroborate, chloride, bromide and bisulfate and in typical organic solvents. Papain displayed much higher enantioselectivity but lower activity in phosphate buffer solution of 1-butyl-3-methylimidazolium tetrafluoroborate BMIM·BF₄ than in other media tested (i.e. E=100, V ₀=0.21 mM min^-1 in BMIM·BF₄, E=2, V ₀=0.43 mM min^-1 in phosphate buffer, E=14-92, V ₀=0.22-0.25 mM min^-1 in organic solvents for D,L-phenylglycine methyl ester). The influence of BMIM·BF₄ on enzyme activity and enantioselectivity also varied with the substrate and the enzyme used. All of the enzymes assayed showed no activity or low enantioselectivity in the ILs with anions including chloride, bromide and bisulfate.     

昆虫病原真菌长孢蜡蚧菌TF-2菌株对豌豆蚜的侵染过程和致病力

【目的】豌豆蚜Acyrthosiphon pisum是世界性的重要农业害虫,给豆类作物造成巨大的经济损失。本研究在前期筛选已获得豌豆蚜致病菌长孢蜡蚧菌Lecanicillium longisporum TF-2菌株的基础上,检测了该致病菌分生孢子对豌豆蚜的毒力效用及侵染方式,以期为利用昆虫病原真菌防治豌豆蚜提供理论基础。【方法】采用离体叶片饲养法检测在不同浓度长孢蜡蚧菌TF-2菌株孢子悬浮液(1.0×10³～1.0×10⁷孢子/mL)中浸渍后对豌豆蚜成虫的致病力;应用扫描电镜和体视显微镜观察豌豆蚜成虫接种TF-2菌株(1.0×10⁷孢子/mL)后长孢蜡蚧菌TF-2菌株侵染症状和侵染过程。【结果】不同浓度长孢蜡蚧菌TF-2菌株分生孢子浸染豌豆蚜成虫致病力随分生孢子浓度升高而逐渐增强,侵染后6 d对豌豆蚜成虫的半致死浓度(LC₅₀)为3.26×10⁴孢子/mL,最高浓度分生孢子(1.0×10⁷孢子/mL)对豌豆蚜成虫的半致死时间(LT₅₀...     

Phenotypic analysis of the ccp1Delta and ccp1Delta-ccp1W191F mutant strains of Saccharomyces cerevisiae indicates that cytochrome c peroxidase functions in oxidative-stress signaling

Yeast cytochrome c peroxidase (CCP) efficiently catalyzes the reduction of H₂O₂ to H₂O by ferrocytochrome c in vitro. The physiological function of CCP, a heme peroxidase that is targeted to the mitochondrial intermembrane space of Saccharomyces cerevisiae, is not known. CCP1-null-mutant cells in the W303-1B genetic background (ccp1Δ) grew as well as wild-type cells with glucose, ethanol, glycerol or lactate as carbon sources but with a shorter initial doubling time. Monitoring growth over 10 days demonstrated that CCP1 does not enhance mitochondrial function in unstressed cells. No role for CCP1 was apparent in cells exposed to heat stress under aerobic or anaerobic conditions. However, the detoxification function of CCP protected respiring mitochondria when cells were challenged with H₂O₂. Transformation of ccp1Δ with ccp1^W191F, which encodes the CCP^W191F mutant enzyme lacking CCP activity, significantly increased the sensitivity to H₂O₂ of exponential-phase fermenting cells. In contrast, stationary-phase (7-day) ccp1Δ-ccp1^W191F exhibited wild-type tolerance to H₂O₂, which exceeded that of ccp1Δ. Challenge with H₂O₂ caused increased CCP, superoxide dismutase and catalase antioxidant enzyme activities (but not glutathione reductase activity) in exponentially growing cells and decreased antioxidant activities in stationary-phase cells. Although unstressed stationary-phase ccp1Δ exhibited the highest catalase and glutathione reductase activities, a greater loss of these antioxidant activities was observed on H₂O₂ exposure in ccp1Δ than in ccp1Δ-ccp1^W191F and wild-type cells. The phenotypic differences reported here between the ccp1Δ and ccp1Δ-ccp1^W191F strains lacking CCP activity provide strong evidence that CCP has separate antioxidant and signaling functions in yeast.