Chromosome numbers in Malawian Commelinaceae

In this account chromosome numbers of 22 species and varieties from five genera of Commelinaceae occurring in Malawi are given. For 14 of them this is the first time their chromosome numbers have been reported. A wide range of chromosome numbers of 2n = 26 , 28, 30. 44. 52 and 60 is noted in Commelina.     

Self-incompatibility in the Commelinaceae

This paper reports on a survey of self-incompatibility in 110species of 22 genera in the family Commelinaceae. Genera fromboth tribes, Tradescantieae and Commelineae are included. Fifty-fivespecies were found to be self-incompatible, 50 species self-compatible,and five species comprised individuals which were self-incompatibleand individuals which were self-compatible. This variabilityand its possible evolutionary significance are discussed. Self-incompatible species had actinomorphic flowers and themajority of these were in the Tradescantieae. Species with zygomorphicflowers which were more commonly found in the Commelineae wereself-compatible. The ubiquitous presence of binucleate pollengrains supports previous data that self-incompatibility is ofthe gametophytic type. The site of pollen tube arrest, however,was on the stigma at or near the base of the stigma papillacells. There were two exceptions to this viz. an unnamed Dichorisandraspecies and Siderasis fuscata where pollen tube arrest was stylar. The significance of these data to taxonomy also receives comment. Commelinaceae, incompatibility, self-compatibility     

孔药花属(鸭跖草科)的核型研究

本文首次对鸭跖草科孔药花属Porandra Hong进行染色体研究。孔药花P．ramosa Hong和攀缘孔药花P．scandens Hong在染色体的大小、数目和形态上都十分相似,核型公式为2n＝36＝4m+26sm+6st(2sat),核型类型属于3B。染色体证据支持孔药花属与穿鞘花属Amischotolype和Coleotrype属相近的观点。     

Karyotype differentiation in three species of Tripogandra Raf. (Commelinaceae) with different ploidy levels

Most species of the genus Tripogandra (Commelinaceae) are taxonomically poorly circumscribed, in spite of having a relatively stable basic number x = 8. Aiming to estimate the cytological variation among Tripogandra species carrying this base number, several structural karyotypic characters were investigated in the diploid T. glandulosa, the hexaploid T. serrulata, and the octoploid T. diuretica. A careful evaluation of chromosome size and morphology did not reveal clear chromosome homeologies among karyotypes. The mean chromosome size was strongly reduced in the octoploid species, but not in the hexaploid species. They also differed largely in the CMA(+) banding pattern and in the number of 5S and 45S rDNA sites per monoploid chromosome complement. All three species showed proximal DAPI (+) heterochromatin, although in T. serrulata this kind of heterochromatin was only visible after FISH. Further, the meiosis in T. serrulata was highly irregular, suggesting that this species has a hybrid origin. The data indicate that, in spite of the conservation of the base number, these species are karyologically quite different from each other.     

竹叶吉祥草（鸭跖草科）的核型研究

本文对鸭跖草科的竹叶吉祥草（Ｓｐａｔｈｏｌｉｒｉｏｎｌｏｎｇｉｆｏｌｉｕｍ（Ｇａｇｎｅｐ．）Ｄｕｎｎ）进行了染色体研究．其染色体大型,数目为２ｎ＝２０;核型公式为２ｎ＝４ｓｍ＋１４ｓｔ＋２ｔ（ｓａｔ）．为首次报道。这支持了竹叶吉祥草属和竹叶子属是两个亲缘关系较近,但同时又是两个分明不同的属的观点。     

Systematic significance of cell inclusions in Haemodoraceae and allied families: silica bodies and tapetal raphides

This paper presents the first record of silica deposits in tissues of Haemodoraceae and adds new records of tapetal raphides in this family. Within the order Commelinales, silica is present in leaves of three families (Hanguanacaeae, Haemodoraceae and Commelinaceae), but entirely absent from the other two (Pontederiaceae and Philydraceae). Presence or absence of characteristic cell inclusions may have systematic potential in commelinid monocotyledons, although the existing topology indicates de novo gains and losses in individual families. Silica sand was observed in leaves of five out of nine genera examined of Haemodoraceae, predominantly in vascular bundle sheath cells and epidermal cells. Within Haemodoraceae, silica is limited to subfamily Conostylidoideae. The occurrence of silica in Phlebocarya supports an earlier transfer of this genus from Haemodoroideae to Conostylidoideae. The presence of raphides (calcium oxalate crystals) in the anther tapetum represents a rare character, only reported in a few monocot families of the order Commelinales, and possibly representing a mechanism for regulation of cytoplasmic free calcium levels. Tapetal raphides were observed here in Anigozanthus and Conostylis (both Haemodoraceae), and Tradescantia (Commelinaceae), thus supplementing two earlier records in Haemodoraceae, Philydraceae and Commelinaceae.     

Cytotaxonomy of Commelinaceae: chromosome numbers of some African and Asiatic species

Chromosome counts are reported for 32 taxa (31 species and 1 subspecies) belonging to 10 genera of Commelinaceae from seven African and Asiatic countries. Counts for 13 species and 1 subspecies are recorded for the first time. Published chromosome numbers for Anhicopsis and Polyspatha are confirmed. It is suggested that Pdisota, Pollia and Stanfieldidla each has a single basic number (x = 20, 16 and 11, respectively). The known cytological diversity in Floscopa is extended. The third continental African species of Coleolrype is found to have the same chromosome number (2n = 36) as the other two. The preponderance of the basic number x = 15 in Commelina is supported. The uncommon basic number x = 13 is reported in four taxa of Cyanotis together with karyotypic differences. The basic number x = 6 is found in a second species of Murdannia . Karyotypic data in addition to chromosome numbers are presented for 24 of the 32 taxa investigated. Karyotypes are found to be useful in assessing relationships in the family, and evolutionary trends in the karyotype are noted.     

Two distinctive anthocyanin patterns in the commelinaceae

A survey of lead and flower anthocyanins in a representative sample (28 spp./10 genera) of the Commelinaceae has shown that the dominant anthocyanin is cyanidin 3,7,3′-triglucoside, acylated with caffeic acid. Acylation with other hydroxycinnamic acids also occurs. As a flower pigment, this anthocyanin is stabilized at the pH of the cell sap by the presence of the three acyl substituents attached through glucose. In Gibasis, the related delphinidin triglucoside is also present. By contrast, the genus Commelina is distinguished by uniformly containing p-coumaroyl-delphinidin 3,5-diglucoside, which is stabilized in flowers as a copigment complex with glycoflavone. There are thus two distinctive sources of blue flower colour in the family. Furthermore, the presence of these rare acylated glucosides clearly separates the Commelinaceae from all other monocotyledonous groups.     

鸭跖草科杜若(Pollia japonica Thunb.)的减数分裂研究

首次对鸭跖草科杜若(Pollia japonicaThunb.)进行了花粉母细胞减数分裂观察,并重新报道了该种的染色体数目为2n=32。结果显示,减数分裂中期I构型为16Ⅱ,并且观察到次级联会现象。减数分裂后期I和后期Ⅱ存在落后染色体、染色体断片、二次分裂不同步等异常现象,统计各时期畸形率都低于10%。随机统计花粉粒活性,成熟率达到90%以上。这说明杜若的减数分裂过程基本正常,也证明了2n=32的体细胞染色体数目是可信的。     

Chromosomal evolution in the South American Riodinidae (Lepidoptera: Papilionoidea)

We give the haploid chromosome numbers of 173 species or subspecies of Riodinidae as well as of 17 species or subspecies of neotropical Lycaenidae for comparison. The chromosome numbers of riodinids have thus far been very poorly known. We find that their range of variation extends from n =?9 to n =?110 but numbers above n =?31 are rare. While lepidopterans in general have stable chromosome numbers, or variation is limited at most a subfamily or genus, the entire family Riodinidae shows variation within genera, tribes and subfamilies with no single modal number. In particular, a stepwise pattern with chromosome numbers that are about even multiples is seen in several unrelated genera. We propose that this variation is attributable to the small population sizes, fragmented populations with little migration, and the behavior of these butterflies. Small and isolated riodinid populations would allow for inbreeding to take place. Newly arisen chromosomal variants could become fixed and contribute to reproductive isolation and speciation. In contrast to the riodinids, the neotropical Lycaenidae (Theclinae and Polyommatinae) conform to the modal n =?24 that characterizes the family.     

A Synopsis of Chromosome Number Variation in the Cyperaceae

The Cyperaceae are well known for having a large amount of variation in chromosome numbers both within and among genera. Most of this variation has been previously attributed to agmatoploid or qualitative aneuploid chromosome number change. To date there have been 4,231 reported chromosome number counts in the family. Despite the large number of counts made, they only represent approximately 16% of the species currently recognized. These counts are here presented in an indexed list with standardized nomenclature following a draft copy of the World Checklist of Cyperaceae. Additionally, I explore variation within genera where a significant number of counts have been made. Given the distributions of counts within genera there is evidence for both agmatoploid and polyploid chromosome number changes.     

Evidence for Balanced Linkage of X Chromosome Polygenes in a Natural Population of Drosophila

Extensive levels of polygenic variation can be maintained in a population without creating a severe segregational load. One way to account for this is that the alleles are arranged on a chromosome so that different regions balance each other phenotypically. To test whether this occurs in a natural population, we isolated ten Drosophila melanogaster X chromosomes and mapped regions of polygenic activity affecting sternopleural bristle number. The chromosomes fell into a small number of groups based upon the similarity of their distributions of polygenic activity. The results are consistent with a model in which a large proportion of the variation can be attributed to a small number of segregating chromosome regions and in which the chromosomes show internal balance.     

Quantitative analysis of the variability of nucleolar organizer regions in Salmo trutta

A quantitative analysis combined with Ag staining was carried out to study the size variation of the main nucleolar organizer region (NOR) bearing chromosome pair 11 of Salmo trutta. A standardized NOR size measurement was developed by comparing the length of the short arm (NOR-bearing region) to the total chromosome length. Statistical procedures support arguments for the existence of a large and structural polymorphism within this species for this chromosome region. A minimum of five different chromosome classes were identified, which account for the total variation found. Size variation among classes was due both to changes in the number of NOR clusters as well as to the amount of rDNA genes within each cluster. NOR size values were normally distributed in the sample analyzed.     

Isolation and characterization of a major tandem repeat family from the human X chromosome.

We report the identification and characterization of a family of repeated restriction fragments whose molecular organization is apparently specific to the human X chromosome. This fragment, identified as an ethidium bromide-staining 2.0 kilobase (kb) band in BamHI-digested DNA from a Chinese hamster-human somatic cell hybrid containing a human X chromosome, has been cloned into pBR325 and characterized. The 2.0 kb repeated family has been assigned to the Xp11 leads to Xq12 region on the X by Southern blot analysis of somatic cell hybrids and is predominantly arranged in tandem clusters of up to seven 2.0 kb monomers. Homologous DNA sequences, not organized as 2.0 kb BamHI fragments, are found elsewhere on the X chromosome and on at least some autosomes, but are not found on the Y chromosome. From a dosing experiment using various amounts of the cloned repeat, we estimate that there are 5,000-7,500 copies of the 2.0 kb BamHI repeat per haploid genome. Since the vast majority, if not all, of these are confined to the X chromosome, this repeated DNA family must account for 5-10% of all X chromosome DNA and must constitute the major sequence component of the pericentromeric region of the X.     

Organizational variation of DYZ1 repeat sequences on the human Y chromosome and its diagnostic potentials

The long arm of the human Y chromosome is flecked with various fractions of repetitive DNA. DYZ1 is one such fraction, which is organized tandemly as an array of a 3.4-kb repeat ranging from 2000-4000 copies in normal males. We have studied the organizational variation of the DYZ1 fraction on the human Y chromosome using DNA samples from CEPH family members and the random population employing the RFLP approach, fluorescence in situ hybridization (FISH), and conducted a similarity search with GenBank sequences. Typing of genomic DNA using DYZ1 as a probe showed an allele length and copy number variations even between two male siblings. Hybridization of DNA from monochromosome hybrids with this probe showed its presence on chromosome 15 in addition to the Y chromosome. Fluorescence in situ hybridization of metaphase chromosomes from an apparently normal male showed DYZ1 sequences in the proximal region of chromosome 11 in addition to the long arm of the Y chromosome. Typing of sets of semen and blood DNA samples from the same human individuals showed discernible allelic variation between the two samples, indicating tissue-specific programmed sequence modulation. DYZ1 seems to be the first probe having the unique potential to discriminate unequivocally the difference between the DNA originating from semen and blood samples, and may be exploited in forensic cases. This probe may also be used as a diagnostic tool to ascertain Y chromosome mosaicism in patients (e.g., Turner), its aberrant status in somatic cells, and possible sequence modulation/rearrangement in the germline samples. Additionally, this can be used to uncover sequence polymorphism in the human population.     

Nucleotide Variation and Divergence in the Histone Multigene Family in Drosophila Melanogaster

Nucleotide differences in the histone H3 gene family in Drosophila melanogaster were studied on three levels: (1) within a chromosome, (2) within a population and (3) between species (D. melanogaster and Drosophila simulans). The average difference within the H3 gene within a chromosome was 0.0040 per nucleotide site, about 52% of that within a population (0.0077). The proportion of divergent sites between the two species was 0.0575, which is about 8.5 times the difference within a species. The distribution of divergence between species was similar to that of variation within a species. Divergence and variation were noted to be greatest in the 3' noncoding region and least in the coding region. Values intermediate between these were found for the 5' noncoding region. Divergence and variation in silent sites exceeded those in the total coding region, thus indicating possible purifying selection for amino-acid-altering change. Phylogenetic relations among H3 genes and genetic differences on these three levels are evidence for the concerted evolution of the histone gene family. The molecular mechanism by which variation is produced and maintained is discussed.     

Population genetics of the Y chromosome of Drosophila melanogaster: rDNA variation and phenotypic correlates

One means of examining the evolutionary significance of molecular variation on the Y chromosome is to identify phenotypes specifically affected by Y-linked genes, and to quantify the phenotypic variation and its correlation to the molecular variation. The functional importance of the Y-linked array of rRNA genes is demonstrated by the ability of Y chromosome to rescue X-linked bobbed lethal alleles, whose lethality is seen in homozygous females. Because low numbers of X-linked rDNA gene copies result in increased developmental time and shortened bristles, and because there is considerable natural variation in Y-linked copy number, a careful examination of Y-linked variation in these two traits may uncover a mode of selection acting on the multigene family. In this study, 36 Y-chromosome replacement lines were tested to detect subtle variation in bristle phenotypes and developmental rates. Correlations among these traits, rDNA gene copy number, and intergenic sequence length were quantified. The absence of significant correlations between phenotypic characters and rDNA copy number of intergenic sequence length suggests that the extant molecular variation in Y-linked rDNA can have at most very small selective effects.     

A Survey of Karyological Phenomena in the Juncaceae with Emphasis on Chromosome Number Variation and Evolution

The order Poales is well known for the presence of holocentric chromosomes, agmatoploidy, symploidy, polyploidy and high variation in chromosome numbers among and within species and genera. The second largest family of this order, Cyperaceae, is very well characterized both karyologicaly and cytologicaly. On the other hand, a smaller family Juncaceae is not so widely investigated from this point of view. The currently known chromosome numbers of the species of all eight genera of the Juncaceae are presented and variation among them is explored. Distribution of diploids, agmatoploids, agmatopolyploids, polyploids, symploids and aneuploids in the family is discussed in the phylogenetic context. Luzula is the best explored group followed by Juncus and Oreojuncus. However, only very little is known for five other Southern hemisphere genera. Fifty-eight percent of taxa from the Juncaceae are still completely unknown. Three different series of chromosome counts have been found in the Juncaceae, one for Luzula (x?=?6), the second for Oreojuncus (x?=?15) and the third for Juncus (x?=?20) with many agmatoploid and aneuploid derivates. This outline summarizes current knowledge in chromosome count variation and karyological research in the family Juncaceae.     

Localization of the restriction fragment length polymorphism D14S1 (pAW-101) to chromosome 14q32.1 leads to 32.2 by in situ hybridization

The restriction fragment length polymorphism D14S1 is delineated by the cloned, single-copy DNA fragment pAW-101. This cloned fragment can therefore serve as a useful marker for gene linkage studies, and the exact location on the gene map is of great interest. pAW-101 was 3H-labeled and hybridized in situ to normal, prometaphase chromosome preparations. Analysis of the grain distribution shows this fragment to be localized to the long arm of chromosome 14 at band q32. Using lymphoid cell lines with 8;14 reciprocal translocations (q24.1;q32.3) from patients with Burkitt lymphoma, we found that the DNA fragment hybridizes to the rearranged chromosome 14 proximal to the breakpoint. These results localize D14S1 to the region 14q32.1 leads to 32.2 This is consistent with localization of this fragment utilizing somatic cell hybrids and family studies.     

Floral anthocyanins in the genus Puya

A survey of floral anthocyanins among ten species of Puya shows the predominant pigment to be delphinidin 3,7,3′-triglucoside. This is the first report of the natural occurrence of this pigment in a non-acylated form. The occurrence of this unusual glucosylation pattern in Puya supports a close alliance between the Bromeliaceae and Commelinaceae.