HYBRIDIZATION AND CYTOTAXONOMY OF DICENTRA

Biosystematic relationships among species assigned to three subgenera of the genus Dicentra were investigated with respect to hybridization and chromosomal constitution and fertility of the hybrids. Four species of subgenus Dicentra, D. formosa, D. eximia, D. nevadensis, and D. peregrina, were intercrossed in various ways to form diploid, triploid, and tetraploid hybrids. Hybrids at the tetraploid level in this subgenus invariably were highly fertile. Triploid hybrids, as expected, were mostly very sterile. Diploid hybrids varied in this respect, but none was highly fertile. Crosses with two of the remaining four species of subgenus Dicentra produced no hybrids, but abundant seed was obtained in one instance. The two species of the subgenus Chrysocapnos, D. chrysaniha and D. ochroleuca, cross to produce a partially fertile tetraploid hybrid, but cross-pollinations involving these species with those of other subgenera failed. The single species of subgenus Hedycapnos, D. spectablis (diploid) produced no hybrids when cross-pollinated with members of the other two sections. These results are fully concordant with presumed affinities based on morphological similarity In addition, preliminary results of hybridization between the monocotyledonous D. peregrina and a number of dicotyledonous species of Dicentra are reported.     

虎斑颈槽蛇行为的观察

本文报道了虎斑颈槽蛇的行为。虎斑颈槽蛇一般栖息在水域附近。在辽宁省西部地区,１０月份陆续进入冬眠,翌年４月醒眠。以无尾两栖动物为食,采用偷袭和伏击方式捕食。有回缩、逃遁、藏匿和威吓等反捕行为。     

被子植物配子-体细胞杂交研究的进展与展望

Pental和Power于1985年提出用植物的单倍体原生质体,与二倍体体细胞原生质体融合产生三倍体植株,以用于限量基因转移研究的设想"'。次年粘毛烟草（Nicotianaglutinosa川、抱子四分体原生质体与烟草（N．tatacum）的体细胞原生质体融合,就成功地得到了三倍体杂种植株,并被称     

CYTOLOGICAL EVIDENCE OF NATURAL INTERTRIBAL HYBRIDIZATION OF TRIPSACUM AND MANISURIS

A plant with the morphological aspect of Tripsacum zopilotense, collected at Acahuizotla, State of Guerrero, showed a series of irregularities during meiosis. In diakinesis, 18 bivalents and 9 univalents were observed. In the following stages the univalents stayed separated, like a genome with very different chromosomes. The study of irregularities during meiosis suggests that the plant could be a hybrid which originated from a fusion of an unreduced gamete of T. zopilotense having 36 chromosomes with a reduced gamete of Manisuris cylindrica having 9 chromosomes.     

SYNTHESIS AND HYBRIDIZATION PROPERTIES OF RNA CONTAINING 8-CHLOROADENOSINE

ABSTRACT

8-Chloroadenosine (8-Cl-Ado) has shown potential as a chemotherapeutic agent for the treatment of multiple myeloma and certain leukemias. 8-Cl-Ado treatment leads to a decrease in global RNA levels and incorporation of the analog into cellular RNA in malignant cells. To investigate the effects of 8-Cl-Ado modifications on RNA structure and function, an 8-Cl-Ado phosphoramidite and controlled-pore glass support were synthesized and used to introduce 8-Cl-Ado at internal and 3′- terminal positions, respectively. RNA oligonucleotides containing 8-chloroadenine (8-Cl-A) residues were synthesized and hybridized with complementary RNA strands. Circular dichroism spectroscopy of the resulting RNA duplexes revealed that the modified nucleobase does not perturb the overall A-form helix geometry. The thermal stabilities of 8-Cl-Ado modified duplexes were determined by UV thermal denaturation analysis and were compared with analogous natural duplexes containing standard and mismatched base pairs. The 8-Cl-Ado modification destabilizes RNA duplexes by ～5 kcal/mole, approximately as much as a U:U mismatched base pair. The duplex destabilization of 8-Cl-A may result from perturbation of Watson-Crick base pairing induced by conformational preferences of 8-halogenated nucleosides.     

ATTEMPTED HYBRIDIZATION BETWEEN MONOECIOUS AND DIOECIOUS CLONES OF CHARA

The suggestion has been made that within the genus Chara the condition of monoecism or dioecism is of limited taxonomic significance, and that this character reflects only minor genetic variation, rarely sufficient to prevent hybridization between two otherwise similar clones. Objections have been raised to this suggestion. The present investigation was undertaken to determine whether the eggs of dioecious C. rusbyana could be fertilized by sperm from monoecious C sejuncta, monecious C. zeylanica, or dioecious C. kenoyeri; and in turn whether the eggs of C. sejuncta and C. zeylanica could be fertilized by sperm from C. rusbyana. On the basis of 83 crosses involving 28 clones of the four taxa, we conclude that C. rusbyana is genetically isolated from the other three.     

PHENOTYPIC AND GENETIC EFFECTS OF HYBRIDIZATION IN DARWIN'S FINCHES

Morphological consequences of hybridization were studied in a group of three interbreeding species of Darwin's finches on the small Galápagos island of Daphne Major in the inclusive years 1976 to 1992. Geospiza fortis bred with G. scandens and G. fuliginosa. Although interbreeding was always rare (< 5%), sufficient samples of measurements of hybrids and backcrosses were accumulated for analysis. Five beak and body dimensions and mass were measured, and from these two synthetic (principal-component) traits were constructed. All traits were heritable in two of the interbreeding species (G. fuliginosa were too rare to be analyzed) and in the combined samples of F, hybrids and backcrosses to G. fortis. In agreement with expectations from a model of polygenic inheritance, hybrid and backcross classes were generally phenotypically intermediate between the breeding groups that had produced them. Hybridization increased additive genetic and environmental variances, increased heritabilities to a moderate extent, and generally strengthened phenotypic and genetic correlations. New additive genetic variance introduced by hybridization is estimated to be two to three orders of magnitude greater than that introduced by mutation. Enhanced variation facilitates directional evolutionary change, subject to constraints arising from genetic correlations between characters. The Darwin's finch data suggest that these constraints become stronger when species with similar proportions hybridize, but some become weaker when the interbreeding species have different allometries. This latter effect of hybridization, together with an enhancement of genetic variation, facilitates evolutionary change in a new direction.     

CHROMATOGRAPHIC EVIDENCE OF HYBRIDIZATION AND EVOLUTION IN PHLOX MACULATA

Representatives of P. maculata ssp. maculata and P. glaberrima ssp. interior and 36 putative hybrids were collected from a population in central Indiana. Chromatographic analysis revealed the presence of nine diagnostic components in P. maculata ssp. maculata and eight such components in P. glaberrima ssp. interior. Putative F₁ hybrids contained all or most of the parental marker components; markers of the non-recurrent parent were absent in the two classes of putative backcross progeny. The characters of P. maculata ssp. pyramidalis are a composite of those present in P. maculata ssp. maculata and P. glaberrima ssp. interior, and the former is virtually identical to certain hybrids from the population in question. The contention that P. maculata ssp. pyramidalis is a stabilized derivative of natural hybridization between these taxa is substantiated by the presence of all of the diagnostic constituents of the putative parents on its chromatograms. It is the author's opinion that the definitive data which chromatography affords will be invaluable in elucidating the complex pathways of evolution in Phlox.     

EFFECTS OF HYBRIDIZATION AND INBREEDING ON FITNESS IN PHLOX

The effects of interpopulation hybridization, and self-fertilization and immigration on fitness in Phlox drummondii were analyzed in 5 natural field sites. Germination rates, survivorship to flowering, fecundity, and net reproductive rates (R_o) were determined for planted populations of natives, hybrids, aliens, and the products of one and two generations of self-fertilization. At all sites, seed germination was 36% for natives, 35% for hybrids and 28% for aliens. Survivorship for natives was 50%, compared to 49% for hybrids and 41% for aliens. The mean fecundity was 34, 35, and 39 seeds per plant for natives, hybrids, and aliens, respectively. The R_o of natives averaged 5.2 vs. 6.4 for hybrids and 4.2 aliens. At all the sites, germination averaged 25% for self-1 plants and 19% for self-2 plants compared to 24% for open-pollinated controls. Survivorship progressed from 50% in the controls to 46% in self-1 and 44% in self-2 plants. Seed production per plant averaged 35% in the control vs. 32% in the self-1 and 25% in the self-2 plants. The mean R_o of the control was 3.8 vs. 3.3 in the self-1 and 2.14 in the self-2 plants. Our results demonstrate that the genetic variable may have a substantial effect on plant fitness in the field.     

HYBRIDIZATION AND FLORAL VASCULARIZATION

Hillson, Charles J. (Pennsylvania State U., University Park.) Hybridization and floral vascularization. Amer. Jour. Bot. 50(10): 971–978. Illus. 1963.—The floral steles of 6 synthetic hybrid mints, representing the F₁ generation of a cross between Mentha spicata strain 199 and Mentha aquatica, were compared with each other and with the steles of the parents. Comparisons of the level of trace divergence, ovary wall vascularization, presence or absence of a nectary, and the nature of the gaps associated with dorsal carpellary bundles show that floral vascularization is an inherited character. Although slight male dominance is indicated in the hybrid steles, anatomical features of both parents are evident. Thus, while vascular tissue may be conservative when phylogenetic reduction of floral parts takes place through adnation and/or connation, stelar modification through hybridization is documented.     

杂交在进化中的作用及杂种的识别和分类处理

所谓杂交和杂种,可以有不同的概念。从最广义的角度来理解,凡基因型不同的个体之间的交配都叫杂交。基因杂合状态是自然界正常的现象。互交繁育的生物体,在正常情况下,在许多位点上都是不同等位基因的杂合体,也就是杂种,它们在自交和杂合时都产生有变异和分离的子代。但杂交最常用的含义是指已有生殖隔离的异种个体或甚至异     

贝壳状革耳菌和黄孢平革菌固体培养酶系比较

白腐菌黄孢平革菌(Phanerochaete chrysosporium) 与贝壳状革耳菌(Panus conchatus)在类似自然状态的固体培养条件下酶的分泌情况有 较大差异。P.conchatus和P.chrysosporium的主要木素降解酶分别是漆酶和锰过氧化物酶 ;两种菌均产生较高水平的木聚糖酶;P.conchatus在整个培养过程中所产生的内切葡 聚糖酶、微晶纤维素酶和纤维二糖酶活力均比P.chrysosporium相应酶的活力低得多, 尤其是内切葡聚糖酶。研究结果初步揭示了P.conchaus降解木素的主要酶系及选择性降 解木素的原因。     

CALLING SONG DISPLACEMENT IN A ZONE OF OVERLAP AND HYBRIDIZATION

The ground crickets Allonemobius fasciatus and A. socius meet in a mosaic zone of overlap and hybridization stretching from the East Coast to at least Illinois. To test whether male calling song differences were enhanced in sympatry, we analyzed the songs of crickets from inside and outside the zone of overlap along two transects. No evidence of calling song displacement was found in A. socius males from populations within the zone of overlap. On the other hand, A. fasciatus displayed calling song displacement in three populations. Our results are consistent with the hypothesis that the selective pressure exerted by the challenge from a related species is frequency dependent. While not a conclusive demonstration, the observed shifts in calling song are strongly suggestive of reproductive character displacement.     

SYNTHESIS AND HYBRIDIZATION OF NOVEL CHIRAL PYRROLIDINE BASED PNA ANALOGUE

Four different PNA fragments containing units of either the R- or S- isomer of N-(2-pyrrolidine-methyl)-N-(thymine-1-acetyl)-glycine (Pmg) were synthesized on a solid support. UV thermal melting experiments with complementary RNAs were performed and it was found that R-Pmg containing PNAs bind better to RNA than those containing the S-Pmg units.     

PHYSIOLOGICAL EVIDENCE OF HYBRIDIZATION AND RETICULATE EVOLUTION IN PHLOX MACULATA

A comparative physiological analysis was conducted on a hybrid swarm involving P. maculata subsp. maculata and P. glaberrima subsp. interior. The population contained an array of segregates and introgressants. Hybrids displayed a high degree of heterogeneity in their physiological attributes, some characters being intermediate to, similar to, or transgressing those of the parental taxa. For example, both net photosynthetic rates and net photosynthetic/dark respiratory ratios were enhanced in the hybrids, and the level of enhancement was associated with the level of morphological intermediacy. Conversely, no enhancement was noted in either respiration rates or foliar fresh weight/ovendry weight ratios of the hybrids. Because of physiological imbalance, about one-third of the hybrids were eliminated early in their development. Representatives of P. maculata subsp. pyramidalis, a putative stabilized derivative of hybridization between the above two parental species, were intermediate in most physiological features and closely resembled some natural hybrids. The data verify that the physiological features of subspecies pyramidalis can be assembled through recombination of the P. maculata and P. glaberrima genomes.     

大鼠颌下腺促性腺激素释放激素及其mRNA的免疫组织化学与原位杂交研究

用免疫组织化学及原位杂交法,研究了促性腺激素释放激素及其ｍＲＮＡ在大鼠颌下腺的分布。结果显示,大鼠颌下腺的浆液性腺泡的上皮细胞,各级导管的上皮细胞及副交感神经节细胞均呈促性腺激素释放激素免疫反应阳性,阳性反应物质分布在胞质,胞核呈阴性反应。颌下腺的浆液性腺泡上皮细胞,各级导管上皮细胞同样被检测到很强的促性腺激素释放激素ｍＲＮＡ杂交信号。以上结果提示,大鼠颌下腺能自身合成促性腺激素释放激素,促性腺激素释放激素对消化功能可能有重要调节作用。