小冰麦杂种落后染色体解凝聚过程的超微结构研究(简报)

70年代发现核小体以来,关于染色质和染色体的超微结构研究有了很大进展,对染色质的高序结构(Higher order structure)已提     

Novel Miscanthus hybrids: Modelling productivity on marginal land in Europe using dynamics of canopy development determined by light interception

New biomass crop hybrids for bioeconomic expansion require yield projections to determine their potential for strategic land use planning in the face of global challenges. Our biomass growth simulation incorporates radiation interception and conversion efficiency. Models often use leaf area to predict interception which is demanding to determine accurately, so instead we use low-cost rapid light interception measurements using a simple laboratory-made line ceptometer and relate the dynamics of canopy closure to thermal time, and to measurements of biomass. We apply the model to project the European biomass potentials of new market-ready hybrids for 2020–2030. Field measurements are easier to collect, the calibration is seasonally dynamic and reduces influence of weather variation between field sites. The model obtained is conservative, being calibrated by crops of varying establishment and varying maturity on less productive (marginal) land. This results in conservative projections of miscanthus hybrids for 2020–2030 based on 10% land use conversion of the least (productive) grassland and arable for farm diversification, which show a European potential of 80.7–89.7 Mt year⁻¹ biomass, with potential for 1.2–1.3 EJ year⁻¹ energy and 36.3–40.3 Mt year⁻¹ carbon capture, with seeded Miscanthus sacchariflorus × sinensis displaying highest yield potential. Simulated biomass projections must be viewed in light of the field measurements on less productive land with high soil water deficits. We are attempting to model the results from an ambitious and novel project combining new hybrids across Europe with agronomy which has not been perfected on less productive sites. Nevertheless, at the time of energy sourcing issues, seed-propagated miscanthus hybrids for the upscaled provision of bioenergy offer an alternative source of renewable energy. If European countries provide incentives for growers to invest, seeded hybrids can improve product availability and biomass yields over the current commercial miscanthus variety.     

GENETIC DIFFERENTIATION OF POLISH POPULATIONS OF SOREX ARANEUS L. III. INTERCHROMOSOMAL RECOMBINATION IN A HYBRID ZONE

Two parapatric chromosomal races of the common shrew (Sorex araneus) in Poland differ in their complement of metacentric arm combinations: hk, io, gr, nm (race IV), and hi, ko, gm, np (race II). In hybrids, these eight race-diagnostic metacentrics form two randomly segregating complexes. The first complex (C₁) occurs in the form of a ring configuration ok/kh/hi/io, or a chain o/ok/kh/hi/i (when there is Robertsonian polymorphism of the element io). The second complex (C₂) always takes the form of a six-element chain configuration r/rg/gm/mn/np/p. The C₂ complex may be shortened to five or even four elements, when acrocentrics g, m and n are present. In the contact zone we found shrews of pure races (race II or IV), as well as hybrids with C₁ or C₂ complexes, and recombinants hi, ko, gr, nm. Complex heterozygotes are likely to suffer reduced fertility due to malsegregation at meiosis. However, the C₁ hybrids with ring configurations occur with a high frequency throughout the contact zone. This suggest that their fitness is only slightly lowered relative to pure race individuals, in contrast to the hybrids with C₁ or C₂ chain configurations, which presumably have a more heavily reduced fertility. On the other hand, at the center of the zone there is a high proportion of recombinants, which, being chromosomal homozygotes, should display normal meiotic segregation. Furthermore, the high frequencies of recombinants within the contact zone should facilitate gene flow between the races. The occurrence of recombinants plays a similar role as the appearance of the maximum frequencies of acrocentric homozygotes described in several contact zones of S. araneus.     

REGENERATION AND SEXUAL DIFFERENTIATION OF GRIFFITHSIA JAPONICA (CERAMIACEAE,RHODOPHYTA) THROUGH SOMATIC CELL FUSION1

Hybrid cells were obtained from somatic cell fusion among male, female, and tetrasporangial plants in Griffithsia japonica Okamura by a wound-healing process. Isolated fusion cells regenerated new mature plants with mixed reproductive structures. The plants regenerated from hybrid cells between male and female plants developed into 1) spermatangiate, 2) carpogonial, 3) bisexual with spermatangia and carpogonial branches, 4) mixed-phase with spermatangia and tetrasporangia, or 5) bisexual/mixed-phase plants with spermatangia, carpogonial branches, and tetrasporangia. About 70% of the plants regenerated from hybrid cells between male and female plants produced tetrasporangia that were always formed with spermatangia on a single cell. Some of those tetrasporangia released tetraspores, six of which gave rise to mature plants. The plants regenerated from hybrid cells between male and tetrasporangial plants developed into spermatangiate, tetrasporangiate, or mixed-phase plants with spermatangia and tetrasporangia. The plants regenerated from hybrid cells between female and tetrasporangial plants developed into carpogonial, tetrasporangiate, or mixed-phase plants with carpogonial branches and tetrasporangia. All types of reproductive structures we re functional.     

The applicability of the plant vigor and resource regulation hypotheses in explaining Epiblema gall moth–Parthenium weed interactions

A basic question in insect–plant interactions is whether the insects respond to, or regulate plant traits, or a complex mixture of the two. The relative importance of the directions of the influence in insect–plant interactions has therefore been articulated through both the plant vigor hypothesis (PVH) and the resource regulation hypothesis (RRH). This study tested the applicability of these hypotheses in explaining the interactions between Parthenium hysterophorus L. (Asteraceae) and its stem‐galling moth, Epiblema strenuana Walker (Lepidoptera: Tortricidae). Parthenium plants exposed to galling were sampled at three sites in north Queensland, Australia, over a 2‐year period, and the relationship between gall abundance and plant vigor (plant height, biomass, flowers per plant, and branches per plant) was studied. To test the predictions of PVH and RRH, the vigor of parthenium plants protected from galling using insecticides was compared to galled plants and plants that escaped from galling. The vigor of ungalled plants was less than the vigor of galled plants. The higher plant vigor in galled plants was not due to galling, as was evident from insecticide exclusion trials. The insect seemed to preferentially gall the more vigorous plants. These findings support the predictions of the PVH and are contrary to those of RRH. Since gall abundance is linked to plant vigor, galling may have only a limited impact on the vigor of parthenium. This has implications for weed biological control. If the objective of biological control is to regulate the population of a plant by a galling insect, a preference for more vigorous plants by the insect is likely to limit its ability to regulate plant populations. This may explain the paucity of successes against biocontrol of annual weeds using gall insects.     

Testing the ecological relevance of Daphnia species designations

1. Molecular approaches have increasingly revealed hidden genetic structure within ecologically important species, leading to the creation of sibling species whose ecological relevance is often unclear. A prime example is Daphnia galeata mendotae, which was split into D. dentifera and D. mendotae based on differences at two allozyme loci. 2. In a set of lake populations in Michigan USA, we test the geographical and temporal consistency of the genetic structure underlying this species split. We also test the morphological relevance of this molecular variation and its ecological significance in lakes. In essence, we ask: does recognition of these new species provide valuable information for plankton ecologists? 3. We found that D. dentifera and D. mendotae represent morphologically and ecologically distinct forms that are distributed among lakes in non‐random fashion, which were remarkably stable over 6 years. Key differences between the species concern their body and head shape, vertical habitat use within lakes and distribution among lakes of different size. We hypothesise that these differences represent specialisation to habitats that differ in risk of invertebrate predation. 4. Reproductive barriers alone are insufficient to explain the pattern of genetic structure; in some lakes complete introgression is apparent. However, parent species and hybrids exhibit a stable co‐existence in many lakes, which suggests that ecological specialisation reinforces divergence within this taxon.     

Life history patterns of parental and hybrid Daphnia differ between lakes

1. We investigated whether Daphnia galeata × hyalina hybrids of Lake Constance and Lake Greifensee show the same pattern of life history parameters as previously reported for D. galeata × cucullata hybrids and whether such a pattern is consistent between Daphnia populations from those two lakes. 2. Hybrids in Lake Constance were intermediate in size compared with the parental species. Hybrids in Lake Greifensee were smaller than D. galeata. The intrinsic growth rate (r) of hybrids from Lake Constance was not significantly different from the faster growing parental taxon D. galeata. However, r of hybrids from Lake Greifensee was significantly lower than that of D. galeata. 3. The observed juvenile body length differences between the taxa varied with the clutch number. The first clutch juvenile lengths of the three taxa did not differ for Lake Constance. First clutch juveniles of Lake Greifensee D. galeata were smaller than hybrid first clutch juveniles. The third clutch juvenile length did not differ between taxa from Lake Greifensee, but D. galeata juveniles from Lake Constance were bigger than those of D. hyalina. 4. The life history pattern found in Lake Constance corresponds to previous findings from other studies. The hybrids in this lake combine the faster population growth of one parental species with a relatively small size. In the case of Lake Greifensee hybrids, the relatively large size of first clutch juveniles and the small size of the adults could be interpreted as dual adaptations to invertebrate and fish predation. We speculate that the lower population growth rate of the hybrids is a trade‐off for this twofold protection.     

Production and cytogenetics of intergeneric hybrids between Brassica napus and Orychophragmus violaceus

The intergeneric hybrid between Brassica napus and Orychophragmus violaceus was obtained by means of embryo culture technique with the latter as the pollen parent. The hybrid was morphologically intermediate between its parents, but could produce a lot of seeds when selfed. Somatic separation of the genomes from the two parental species was observed during the mitotic divisions of some of the hybrid cells. Thus, the hybrid became the mixoploid in nature, consisting of haploid and diploid cells of B. napus, and a nuclear — cytoplasmic hybrid, with the cytoplasm of B. napus and the nuclei of O. violaceus, and the hybrid cells. Pollen mother cells with 19, 12 and 6 bivalents, respectively, were produced by the hybrid. From the selfed progeny of the hybrid, mainly two kinds of plants, B. napus and the hybrid, were found. The hybrid plants of the selfed progeny again produced two kinds of plants, B. napus and the hybrid.     

Divergence in cuticular hydrocarbons between parapatric subspecies of the meadow grasshopper, Chorthippus parallelus (Orthoptera, Acrididae)

Two subspecies of the grasshopper Chorthippus parallelus (Orthoptera; Acrididae) meet and form a hybrid zone in the Pyrenees. Here we investigate whether the subspecies differ in the blend of cuticular hydrocarbons. Such differences may function as chemical signals, being detected via contact chemoreception and used during mate choice as in other insects. Gas chromatography shows that the subspecies have diverged in the composition of their cuticular hydrocarbons. This difference between subspecies exists over and above variation in cuticular hydrocarbons among individual populations. The majority of the difference can be attributed to the relative amounts of a small group of compounds present in the cuticle. The possible consequences of this chemical divergence for mating encounters between the subspecies are discussed.