表型与亲本不易区分的茯苓同核体菌株新类型

茯苓Wolfiporia hoelen是我国传统中药材之一,也是一种食药兼用的大型真菌,目前已规模化栽培,但由于其交配系统一直不明确,影响了种质改良。前期我们发现了茯苓的同核体,明确了茯苓的交配系统和生活史,并建立了以培养特性和分子标记区分同核体的方法,但未明确是否适用于茯苓种群的不同个体。在对多个菌株的研究中,发现了同核体表型与亲本不易区分的茯苓菌株。本研究主要以来自日本的菌株775 (NBRC 30628)为亲本,对其同核体菌株进行收集鉴定,并对同核体菌株的培养特性、交配现象和杂交等进行了研究。此类菌株的同核体菌株可通过与亲本对峙培养进行鉴定,但菌丝生长、菌落形态和吃料速度等与亲本没有显著差异,不同交配型的同核体之间交配时没有明显的交配现象。rpb2杂合位点标记可以用于鉴定该类型同核体菌株,且能验证是否交配。该类型同核体与之前发现的同核体类型之间可以进行杂交,杂交菌株可与两亲本都产生拮抗现象。该发现补充了之前建立的茯苓同核体鉴定方法,加深了对茯苓物种群体的了解,同时丰富了茯苓的育种资源。     

Variation in Copper Tolerance among Homokaryotic and Dikaryotic Mycelia of Polyporus palustris Berk. et Curt.

Investigations were made of the variation in copper toleranceamong homokaryons and dikaryons originating from one dikaryoticisolate of Polyporus palustris, as shown by their growth onnutrient agar containing copper sulphate, usually at 0.32 Mconcentration (c. 8 per cent of CuSO₄.5H₂O). Homokaryons obtainedby monobasidiospore isolation were crossed and further homokaryonsobtained in the same way. Selection for copper tolerance gavean increase in the second generation, but no further increasein the third; whilst selection for copper sensitivity gave substantialincreases in both second and third generations. It is concludedthat copper tolerance in this fungus is controlled by a numberof genes. It was found that, in this fungus, the copper toleranceof a dikaryon was substantially greater than that of eitherof its constituent homokaryons. It was also found that differentisolates of P. palustris varied very widely in copper tolerance.     

Crosses among Homokaryons from Commercial and Wild-Collected Strains of the Mushroom Agaricus brunnescens (= A. bisporus)

A new technique for the production of hybrid strains of the cultivated mushroom Agaricus brunnescens is described. Homokaryons were recovered from regenerated protoplasts obtained from several heterokaryotic strains. A total of 16 novel hybrids were produced in 63 attempted crosses between paired homokaryons. Recovery of both homokaryons and hybrids was verified by analysis of restriction fragment length polymorphisms. Three of four hybrids fruited in small-scale tests, further confirming that the isolates were true hybrids. Colony morphology alone was found to be a poor indicator of hybrid status. In two instances, three homokaryons crossed successfully in all combinations, suggesting that there are at least three alleles at the putative mating-type locus. Crosses between homokaryons from commercial and wild-collected isolates indicated that these strains belong to the same biological species.     

Monandry and polyandry as alternative lifestyles in a butterfly

Butterflies show considerable variability in female mating frequency, ranging from monandrous species to females mating several timesin their lifetime. Degree of polyandry also varies within species,with some females only mating once and others mating multiply.Previous studies have shown that one reason for female multiplemating is to obtain nutritious male donations that both increasethe longevity of females and result in higher lifetime fecundity.Despite the presence of male nutrient donations, some femalesof the green-veined white butterfly (Pieridae: Pieris napi)never mate more than once. In this study, we examined thisapparent paradox. We assessed to what degree polyandry is undergenetic control by a full-sib analysis, and we also estimatedthe broad sense heritability of female lifetime fecundity in singly mated females. Both polyandry and lifetime fecundityhave a genetic component. However, degree of polyandry appearsto be traded off against reduced longevity when denied theopportunity to mate more than once. It is possible that femaleP. napi display different reproductive strategies, with somefemales relying on male donations to realize their potentialfecundity and others relying on their own resources for egg production. In nature, polyandrous females may be preventedfrom mating multiply due to unfavorable weather. We discussthe possibility that the trade-off between degree of polyandryand life span when singly mated may affect the maintenanceof genetic variability in female mating frequency in this species.Possible reasons for these different reproductive strategiesare discussed.     

Molecular genetics of sexual development in the mushroom Coprinus cinereus

Sexual development in the mushroom Coprinus cinereus is under the control of two mating type loci, A and B. When two haploid homokaryons with compatible alleles at both A and B loci are mated, the coordinated activities of A- and B-regulated pathways lead to formation of a mycelium termed the dikaryon, in which the two nuclei from the mating partners pair in each cell without fusing. The dikaryon is a prolonged mycelial stage that can be induced to develop a multicellular structure, the mushroom, under proper environmental conditions. The two nuclei fuse in specialized cells on the mushroom and immediately undergo meiosis to complete the sexual life cycle. It has been established recently that the A genes encode two classes of homeodomain proteins while the B genes encode pheromones and their receptors. More recently, molecular genetics has been used to reveal genes that work downstream of the mating type genes to regulate dikaryon formation, mushroom morphogenesis, and meiosis.     

Blue Light Overrides Repression of Asexual Sporulation by Mating Type Genes in the Basidiomycete Coprinus cinereus

Monokaryotic mycelia of the homobasidiomycete Coprinus cinereus form asexual spores (oidia) constitutively in abundant numbers. Mycelia with mutations in both mating type loci (Amut Bmut homokaryons) also produce copious oidia but only when exposed to blue light. We used such an Amut Bmut homokaryon to define environmental and inherent factors that influence the light-induced oidiation process. We show that the Amut function causes repression of oidiation in the dark and that light overrides this effect. Similarly, compatible genes from different haplotypes of the A mating type locus repress sporulation in the dark and not in the light. Compatible products of the B mating type locus reduce the outcome of light on A-mediated repression but the mutated B function present in the Amut Bmut homokaryons is not effective. In dikaryons, the coordinated regulation of asexual sporulation by compatible A and B mating type genes results in moderate oidia production in light. Copyright 1998 Academic Press.     

Self-incompatibility, Inbreeding Depression and Crossing Potential in Five BrazilianPleurothallis (Orchidaceae) Species

Intra- and interspecific experimental pollinations were madeto determine the mating systems and the interspecific crossingpotential in individuals from 24 populations of five Pleurothallisspecies. Pleurothallis johannensis, P. ochreata and P. teresshow weak or partial self-incompatibility while P. adamantinensisand P.fabiobarrosii are more strictly self-incompatible. Wefound no differences in fruit set between intra- and interpopulationintraspecific crosses, and there was no correlation betweenfruit set and genetic variability or inbreeding in these species.All species are interfertile and showed no correlation betweengenetic similarity and crossing potential. We scored fruitsfor seed viability and observed a strong inbreeding depressionin all populations; however, there was no difference in seedviability among intrapopulation, interpopulation intraspecificand interspecific cross-pollinations. These species are pollinatedby flies with a behavioural pattern that facilitates self-pollination.Self-incompatibility and inbreeding depression are apparentlyimportant in the maintenance of the unusually high levels ofgenetic variability found in these species. As generally observedin other orchid species, barriers to hybridization between thesePleurothallis species are at the level of pollination. Copyright2001 Annals of Botany Company Pleurothallis, Orchidaceae, mating system, self-incompatibility, inbreeding depression, fruit set, seed set, polyembryony, interspecific compatibility     

Genetic evidence for somatic haploidization in developing fruit bodies of Armillaria tabescens

Armillaria spp. have vegetative hyphae with diploid uninucleate cells, but the fruit bodies of many species contain clamped dikaryotic hyphae. Earlier observations suggest that somatic haploidization takes place in developing fruit bodies. To verify this, a uninucleate diploid cell was isolated from each of the 49 mating combinations between single-spore isolates of Armillaria tabescens and they were fruited. Twenty-four isolates produced fruit bodies with at least a partially dikaryotic subhymenium. Dikaryotic hyphae were isolated from fruit-body primordia and homokaryons were obtained by micromanipulation or by protoplasting. Approximately half of the isolates proved to represent recombinant mating types in respect to parent homokaryons, and most of them contained recombinant haploid DNA, based on random-amplified microsatellite markers. The results show that the nuclei in dikaryotic hyphae found in fruit bodies result from somatic haploidization. The mechanism of haploidization remains unclear.     

Analysis of Inbreeding Depression in Agaricus Bisporus

Inbreeding depression was observed in the commercial button mushroom, Agaricus bisporus, by examining two laboratory populations. The outbred population consisted of 20 compatible pairings, 10 homokaryons with each of the homokaryons Ag1-1 and Ag89-65. The inbred population consisted of 104 backcrosses (among which 52 were expected to be sexually compatible) obtained from the pairings of two progenitor homokaryons, Ag1-1 and Ag89-65, with 52 progeny homokaryons derived from the mating between Ag1-1 and Ag89-65. The eight fitness components examined for these two populations were successful matings as identified by the analysis of restriction fragment length polymorphisms, positive mycelial interaction in these successful matings, heterokaryon growth rate, primordium formation by the successful matings, fertile fruiting body formation, time to first break, average number of fruiting bodies per square foot, and average weight per fruiting body. The outcrossed population showed a significant advantage over the inbred population in three of eight fitness components. Two pairs of traits were significantly correlated. The multiplicative fitness ratio of the inbred to the outcrossed population was 0.18. The relevance of inbreeding depression to the evolution of fungal mating systems and to mushroom breeding is discussed.     

Heterokaryon formation with homokaryons derived from protoplasts ofRhizoctonia solani anastomosis group eight

Homokaryons were successfully recovered by regenerating protoplasts prepared from vegetative hyphae of field isolates ofRhizoctonia solani anastomosis group (AG) 8, the causal pathogen of bare-patch disease of cereals. A mating type incompatibility system, which is similar to that reported in AG 1 and AG 4, was demonstrated in AG 8. All homokaryons obtained in AG 8 were able to form tufts with their parent isolates and other heterokaryotic field isolates of AG 8 tested. Heterokaryons were readily recovered from tufts of pairing of certain homokaryon combinations. The synthesized heterokaryons formed tufts with both of the contributing homokaryons. The majority of hyphal tip cultures isolated from tufts resembled one of the contributing homokaryons. These nonheterokaryotic hyphae in tufts are attributed to transient heterokaryon effects.     

Male reproductive success and sexual selection in northern water snakes determined by microsatellite DNA analysis

Male northern water snakes (Nerodia sipedon) have high variancein reproductive success relative to females. We used DNA-basedpaternity analyses from a 3-year study of two marsh populationsof water snakes to investigate the factors that contributeto variation in male success. Male traits investigated includedbody size, condition, tail length, home range size, activityduring the mating season, and genetic profile (genetic similarityto females, heterozygosity, and genetic variability [d²]).We successfully assigned > 80% of offspring to sires froma sample of 811 offspring from 45 litters. Male reproductivesuccess did not vary significantly with body size, tail length,condition, home range size, or the number of microsatelliteloci at which males were heterozygous, nor with other featuresof their genetic profiles. However, we found evidence of positive assortative mating by size in the marsh in which receptive femaleswere not spatially clumped. Also, males that were most activeduring the mating season were more successful, particularlywhere females were not clumped. We failed to find evidenceof selection acting on male size through variance in reproductivesuccess, indicating that sexual selection does not have an important influence on sexual size dimorphism in this species(males are smaller than females). We propose that males aresmaller than females because the lack of advantage to largesize allows males to adopt a low-energy, low-growth strategythat reduces their risk of predation outside the mating season.     

Effect of the proportion of parental nuclei in a heterokaryon on the pattern of gene conversion in Sordaria fimicola

Summary Sordaria fimicola is a homothallic fungus and when a cross is made between two strains a heterokaryotic zone is formed in which the crossing occurs. This grades into homokaryotic regions on either side where self-fertilization occurs within each parent. By selecting clusters of asci from the parts of the heterokaryotic region adjoining the homokaryons it has been found that the pattern of conversion at the grey (g) spore colour locus can differ greatly from one side of the heterokaryotic region to the other. Moreover, this effect of the nuclear composition of the heterokaryon affected alleles h ₅ and g ₇ quite differently. Flanking marker behaviour was also influenced.     

Sexual selection and condition dependence of courtship display in three species of horned dung beetles

Sexual selection has traditionally been divided into competitionover mates and mate choice. Currently, models of sexual selectionpredict that sexual traits are expressed in proportion to thecondition of their bearer. In horned beetles, male contestcompetition is well established, but studies on female preferencesare scarce. Here I present data on male mating success and condition dependence of courtship rate in three species of horn-dimorphicdung beetles, Onthophagus taurus, Onthophagus binodis, andOnthophagus australis. I found that in the absence of malecontest competition, mating success of O. taurus and O. australiswas unrelated to their horn length and body size, whereas inO. binodis horn size had a negative effect but body size hada positive effect on male mating success. Overall, in O. binodismajor morph males had greater mating success than minor morphmales. In all three species male mating success was affectedby courtship rate, and the courtship rate was condition dependent such that when males were manipulated to be in poor conditionthey had lower courtship rates than males that were manipulatedto be in good condition. My findings provide new insight intothe mating systems of horned dung beetles and support an importantassumption in indicator models of sexual selection.     

The notal organ of the scorpionfly (Panorpa vulgaris): an adaptation to coerce mating duration

The notal organ in P. vulgaris (Insecta: Mecoptera) is a clamplikestructure on the dorsum of the middle of the male’s abdomenthat holds one of the female’s forewings throughout mating.Males often provide salivary masses as food to their mates duringmating, and a male’s ability to produce saliva dependsupon whether he has fed adequately before mating. To test thehypothesis that the evolutionary function of the notal organis to coerce longer matings than are in the interests of females,the notal organ and the amount of food males and females receivebefore mating were experimentally manipulated. In support ofthe hypothesis, copulation was reduced when the notal organwas made inoperative under the following four conditions: (1)female fed and male starved before mating, no saliva duringmating; (2) same as in condition 1 but with one salivary massduring mating; (3) both sexes starved before mating, no salivarymass during mating; and (4) both sexes fed before mating. However,when females were starved before mating and males were fed,resulting in multiple masses being provided during mating, thenotal organ had no effect on length of copulation, and thusthere was no sexual conflict over mating duration. In addition,the larger the female relative to her mate, the briefer thecopulation when the notal organ was operative, which suggeststhat a physical struggle between the male and female may occurduring sexual conflict about mating duration. This is one ofonly a few studies that provide evidence of adaptation to thedomain of sexual coercion. [Behav Ecol 1991;2:156–164]     

Preference polymorphism for coloration but no speciation in a population of Lake Victoria cichlids

Female mating preference based on male nuptial coloration hasbeen suggested to be an important source of diversifying selectionin the radiation of Lake Victoria cichlid fish. Initial variationin female preference is a prerequisite for diversifying selection;however, it is rarely studied in natural populations. In clearwater areas of Lake Victoria, the sibling species Pundamiliapundamilia with blue males and Pundamilia nyererei with redmales coexist, intermediate phenotypes are rare, and most femaleshave species-assortative mating preferences. Here, we studya population of Pundamilia that inhabits turbid water wheremale coloration is variable from reddish to blue with most malesintermediate. We investigated male phenotype distribution andfemale mating preferences. Male phenotype was unimodally distributedwith a mode on intermediate color in 1 year and more blue-shiftedin 2 other years. In mate choice experiments with females ofthe turbid water population and males from a clearer water population,we found females with a significant and consistent preferencefor P. pundamilia (blue) males, females with such preferencesfor P. nyererei (red) males, and many females without a preference.Hence, female mating preferences in this population could causedisruptive selection on male coloration that is probably constrainedby the low signal transduction of the turbid water environment.We suggest that if environmental signal transduction was improvedand the preference/color polymorphism was stabilized by negativefrequency-dependent selection, divergent sexual selection mightseparate the 2 morphs into reproductively isolated species resemblingthe clear water species P. pundamilia and P. nyererei.     

Trikaryon formation and nuclear selection in pairings between heterokaryons and homokaryons of the root rot pathogen Heterobasidion parviporum

Pairings between heterokaryons and homokaryons of Agaricomycete fungi (he-ho pairings) can lead to either heterokaryotization of the homokaryon or displacement of the homokaryotic nucleus through migration of nuclei from the heterokaryon into the homokaryon. In species of Agaricomycetes with multinucleate cells (>2 nuclei per cell), he-ho pairings could result in the stable or transient formation of a hypha with three genetically different nuclei (trikaryons). In this study, he-ho pairings were conducted using the multinucleate Agaricomycete Heterobasidion parviporum to determine whether trikaryons can be formed in the laboratory and whether nuclear genotype affects migration and heterokaryon formation. Nuclei were tracked by genotyping the heterokaryotic mycelium using nucleus-specific microsatellite markers. The data indicated that certain nuclear combinations were favored, and that nuclei from some strains had a higher rate of migration. A high percentage of trikaryons (19 %) displaying three microsatellite alleles per locus were identified among subcultures of the he-ho pairings. Using hyphal tip and conidial isolation, we verified that nuclei of three different mating types can inhabit the same mycelium, and one of the trikaryotic strains was judged to be semi-stable over multiple sub-culturing steps, with some hyphal tips that retained three alleles and others that reduced to two alleles per locus. These results demonstrate that nuclear competition and selection are possible outcomes of heterokaryon-homokaryon interactions in H. parviporum and confirm that ratios of component nuclei in heterokaryons are not strictly 1:1. The high rate of trikaryon formation in this study suggests that fungi with multinucleate cells may have the potential for greater genetic diversity and recombination relative to dikaryotic fungi.     

Genetic diversity and population structure of Ascochyta rabiei from the western Iranian Ilam and Kermanshah provinces using MAT and SSR markers

Knowledge of genetic diversity in A. rabiei provides different levels of information that are important in the management of crop germplasm resources. Gene flow on a regional level indicates a significant potential risk for the regional spread of novel alleles that might contribute to fungicide resistance or the breakdown of resistance genes. Simple sequence repeat (SSR) and mating type (MAT) markers were used to determine the genetic structure, and estimate genetic diversity and the prevalence of mating types in 103 Ascochyta rabiei isolates from seven counties in the Ilam and Kermanshah provinces of western Iran (Ilam, Aseman abad, Holaylan, Chardavol, Dareh shahr, Gilangharb, and Sarpul). A set of 3 microsatellite primer pairs revealed a total of 75 alleles; the number of alleles varied from 15 to 34 for each marker. A high level of genetic variability was observed among A. rabiei isolates in the region. Genetic diversity was high (He = 0.788) within populations with corresponding high average gene flow and low genetic distances between populations. The smallest genetic distance was observed between isolates from Ilam and Chardavol. Both mating types were present in all populations, with the majority of the isolates belonging to Mat1-1 (64%), but within populations the proportions of each mating type were not significantly different from 50%. Results from this study will be useful in breeding for Ascochyta blight-resistant cultivars and developing necessary control measures.     

松褐天牛的交配行为

采用室内试验和野外观察相结合的方法,对松材线虫病的主要媒介昆虫松褐天牛Monochamus alternatus Hope的交配行为进行了研究。结果表明： 松褐天牛一次完整的交配包括相遇抱对、插入输精和配后保护3个阶段,在交配过程中雄虫有多次插入输精现象发生。室内试验中共观察到松褐天牛的交配123次,松褐天牛一次完整的交配过程平均需时63.49 min,其中输精前的抱对时间平均为1.68 min,交配过程中每次输精插入时间平均为57.60 s,配后保护时间为15.18 min。松褐天牛在开始交配的4天内平均交配5.15次,不同雄性个体所获得的交配机会差异很大。松褐天牛的交配行为表现出强烈的雄性竞争现象,雄虫能根据雌虫或自身的交配经历调整交配投入,当雌虫或者雄虫是初次交配时,总输精时间和插入输精的次数显著大于与有交配经历的雌虫或雄虫交配时的输精时间和插入输精次数。田间松褐天牛的交配行为与室内观察结果基本一致。     

突尼斯非洲跳鼠(Jaculus jaculus)和埃及跳鼠(J.orientalis)群体的等位酶多态及遗传分化(英文)

运用16种酶蛋白编码的23个遗传座位对突尼斯非洲跳鼠(Jaculus jaculus)和埃及跳鼠(J. orientalis)自然群体的遗传变异和分化进行了电泳分析。结果表明,与其他啮齿动物等哺乳动物的相关数据比较,发现这两个种群体的遗传变异水平较低。非洲跳鼠群体的观测杂合度 (H_obs) 为0.08—0.19,多态座位百分比(P)为26.2%—45.2%,每个座位的平均等位基因数(A)为1.1—1.4;埃及跳鼠的H_obs为0.10—0.15,P为29.3%—44.1%,A为1.1—1.7。两个种群体各自的遗传分化程度较低(非洲跳鼠和埃及跳鼠的F_st分别为0.0017和0.0019)。而两个种群体间的F_st为0.607（P<0.05）,表明两个种之间高度的遗传分化。本研究支持这两个种分类地位的合法性,并强调了地理因素（环境类型和生物气候阶段）对两个种遗传结构的影响。     

水菖蒲活性物质β-辛醚对四纹豆象行为、死亡率和繁殖的影响

在室内条件下研究了水菖蒲Acorus calamus活性物质β-细辛醚对四纹豆象Callosobruchus maculates成虫行为、产卵和繁殖的影响。结果表明：经过β-细辛醚接触处理后的四纹豆象成虫行为主要表现为兴奋→失去平衡→击倒→死亡,接触药剂64 h后,试虫成虫全部死亡。β-细辛醚处理可显著的降低四纹豆象成虫的交配次数,随着处理时间的延长,成虫的交配次数减少,且处理雄虫比处理雌虫对交配竞争能力的影响更大。处理雌虫与未处理雄虫配对后以及处理雄虫与未处理雌虫配对后,雌虫的产卵数均极显著低于对照,且随着处理时间的延长,雌虫的产卵数显著减少,但两种配对处理之间雌虫的产卵数无显著差异。处理雌虫与未处理雄虫配对后以及处理雄虫与未处理雌虫配对后,雌虫产卵的孵化率均显著低于对照处理,但不同处理时间后卵的孵化率无显著差异; 两种配对处理所产卵的孵化率无显著差异。据此得出结论：水菖蒲根茎提取物β-细辛醚为神经毒剂,可以减少四纹豆象的种群数量,具有开发为储粮害虫四纹豆象防治剂的潜力。