Tetraploid Chromosome Research Articles

Heterogeneous circulating tumor cells correlate with responses to neoadjuvant chemotherapy and prognosis in patients with locally advanced breast cancer.

Neoadjuvant chemotherapy (NCT) is the standard treatment for patients with locally advanced breast cancer (LABC). The predictive value of heterogeneous circulating tumor cells (CTCs) in NCT response has not been determined. All patients were staged as LABC, and blood samples were collected at the time of biopsy, and after the first and eighth NCT courses. Patients were divided into High responders (High-R) and Low responders (Low-R) according to Miller-Payne system and changes in Ki-67 levels after NCT treatment. A novel SE-i·FISH strategy was applied to detect CTCs. Heterogeneities were successfully analyzed in patients undergoing NCT. Total CTCs increased continuously and were higher in Low-R group, while in High-R group, CTCs increased slightly during NCT before returning to baseline levels. Triploid and tetraploid chromosome 8 increased in Low-R but not High-R group. The number of small CTCs in Low-R group increased significantly until the last sample, however, remained constant in High-R group. The patients with more CTCs had shorter PFS and OS than those with less CTCs after the eighth course of NCT. Total CTCs following NCT could predict patients' responses. More detailed characterizations of CTC blood profiles may improve predictive capacity and treatments of LABC.

A tetraploid Echinochloa with plagiotropic tillers: Its distribution and habitat in the northern part of the main island of Japan

AbstractAn annual Echinochloa with plagiotropic tillers (semi‐erect type) was found on a paddy levee in Miyagi prefecture in Japan. This semi‐erect type had tetraploid chromosome numbers (2n = 36) and would be expected to be E. oryzicola. However, its appearance was distinct from that of E. oryzicola. To collect seed samples and clarify its distribution and habitat, exploration and collection surveys were carried out in the northern part of Honshu, the main island of Japan in 2014, 2017, and 2018. Thirty‐two populations that were assumed to be the semi‐erect type were found and their mature seeds were collected. Based on the results of chromosome counts and growth form analyses, all of them were confirmed to be the semi‐erect type. The 32 populations were distributed in the prefectures of Aomori, Iwate, Akita, Miyagi, Yamagata, Fukushima, and Niigata, and located in paddy fields, abandoned paddy fields, paddy levees, roadsides, vacant land, and scree slopes. Our surveys indicated that the semi‐erect type grew in wet and dry disturbed habitats at an early stage of secondary succession including paddy fields in the northern part of the main island of Japan.

Karyological and molecular analysis of Leucanthemum (Compositae, Anthemideae) in Corsica

Karyological, flow-cytometric and molecular analyses indicate that the genus Leucanthemum Mill. (Compositae, Anthemideae) is represented in Corsica (Corse) by two species: the tetraploid L. ircutianum DC. and the hexaploid L. corsicum (Less.) DC. The indication of the occurrence of the diploid L. vulgare Lam. on the island and of a tetraploid chromosome number for L. corsicum, given in former treatments of the genus for Corsica, could not be corroborated. AFLP fingerprinting further suggests that the infraspecific taxonomy of L. corsicum with two subspecies (L. corsicum subsp. corsicum and subsp. fenzlii) and three forms (L. corsicum f. corsicum, f. pinnatifidum and f. eschenlohrianum), which is mainly based on differences in the degree of leaf dissection, is not backed by genetic discontinuities. Owing to the observed little variation in leaf dissection within populations in the wild and the constancy of these features under cultivation, we propose the rank of varieties to taxonomically acknowledge these different stages in the broad spectrum of leaf-dissection grades exhibited by L. corsicum. As a consequence, the two new combinations L. corsicum var. eschenlohrianum (Gamisans) Vogt, Hugot & Oberpr. and L. corsicum var. fenzlii (Gamisans) Vogt, Hugot & Oberpr. are proposed.

Cytogenetics and genetic introgression from wild relatives in soybean

Cultivated soybean, wild soybean, and 23 perennial Glycine species contain 2n = 40 chromosomes. Accessions of G. hirticaulis and G. tabacina have diploid (2n = 40) and tetraploid (2n = 80) chromosome numbers. In contrast, G. tomentella includes accessions with four cytotypes (2n = 38, 40, 78, or 80). Meiosis of G. max and G. soja F1 is normal and gene exchange is easy. Occasionally, accessions of the two species differ by chromosome structural changes (reciprocal translocation/paracentric inversion). The segregating populations inherit undesirable traits such as vining, lodging susceptibility, lack of complete leaf abscission, seed shattering, and small black coated seeds because of genetic drag. The introgression of useful genes from 26 wild perennial Glycine species to soybean has been restricted because of crossability barriers and requires extensive hybridization, immature seed rescue, and cytogenetic manipulations. This review paper discusses cytogenetics, gene pools of the soybean and the production of fertile G. max plants using 78-chromosome G. tomentella (PI 441001) as a paternal and maternal parent in crosses with G. max cv. ‘Dwight’ (2n = 40). Thus, reporting breaking of the intersubgeneric crossability barriers for the first time.

Detecting and phenotyping of aneuploid circulating tumor cells in patients with various malignancies

ABSTRACTCirculating tumor cells (CTCs) have been exclusively studied and served to assess the clinical outcomes of treatments and progression of cancer. Most CTC data have mainly been derived from distinct cohorts or selected tumor types. In the present study, a total of 594 blood samples from 479 cases with 19 different carcinomas and 30 healthy samples were collected and analyzed by Subtraction enrichment method combined with immunostaining-fluorescence in situ hybridization (iFISH). Non-hematopoietic cells with aneuploid chromosome 8 (more than 2 copies) were regarded as positive CTCs. The results showed that none of CTCs was found in all 30 healthy samples. The overall positive rate of CTCs was 89.0% in diagnosed cancer patients (ranging from 75.0% to 100.0%). Average number of 11, 5, 8 and 4 CTCs per 7.5 mL was observed in lung cancer, liver cancer, renal cancer and colorectal cancer, respectively. Among 19 different carcinomas, the total number of CTCs, tetraploid chromosome 8, polyploid chromosome 8, CTM (Circulating tumor microemboli) and large CTCs in patients with stage Ⅲ and Ⅳ were statistically higher than patients with stage Ⅰ and Ⅱ (P < 0.05). Furthermore, EpCAM expression was more frequently found in most CTCs than vimentin expression, confirming that these CTCs were of epithelial origin. In addition, small and large CTCs were also classified, and the expression of vimentin was mostly observed in small CTCs and CTM. Our results revealed that there are higher numbers of CTCs, tetraploid, polyploid and large CTCs in patients with stage Ⅲ and Ⅳ, indicating that the quantification of chromosome ploidy performed by SE-iFISH for CTCs might be a useful tool to predict and evaluate therapeutic efficacy as well as to monitoring disease progression.

Abstract B12: Differences in neoplastic transformation potential between OSE and FTE

Abstract Introduction: The most common and aggressive histotype of ovarian cancer is high-grade serous carcinoma (HGSC), which accounts for approximately 90% of deaths. Furthermore, the risk of developing HGSC is increased by having a mutation in the BRCA1 and BRCA2 gene. There is considerable evidence detailing the fallopian tube epithelia (FTE) as the site of origin of the disease, yet the ovarian surface epithelium (OSE) is still proposed as the site of origin by some. Currently, no studies have compared in vivo/xenografts models derived from FTE and OSE of BRCA mutation carriers. We suggest that in vivo/xenograft models can prove a useful tool for understanding the disease origins, meanwhile accounting for the genetic characteristics of the disease. Methodology: Immortalized and transformed cell lines, from both FTE and OSE, were derived from both BRCA1 and BRCA2 mutation carriers and non-carriers. In particular, 16 OSE cell lines were created--3 from BRCA1 carriers and noncarriers. Cell lines were transfected with hTERT and SV40, and either vectors overexpressing cMYC and hRASV12. 8 of these lines with cMYC or hRASV12 were injected into the mammary fat pad of 6-week-old female NSG mice (NOD.Cg-Prkdcscid). Similarly, 16 FTE lines were generated from 2-BRCA1 and 1 BRCA2 heterozygous mutation and 3 non-BRCA carriers overexpressing hTERT and SV40 with either cMYC or hRASV12. Results: To date, tumors have developed from mice injected with ovarian surface epithelial cells and fallopian tube epithelial cells at the mammary fat pad and the intraperitoneal cavity. FTE cells injected intraperitoneally produced ascites and displayed tumors lining the abdominal cavity and major organs. The parental immortal lines of 4 cases were karyotyped: FTE-37 and FTE-19 (controls); FTE-13 (BRCA2 mutant) and FTE-98 (BRCA1 mutant) cell lines demonstrated varying types of tetraploidy while the control (BRCA wild type) had fewer tetraploid chromosomes. Western blot analyses demonstrated that tumors express PAX8 and epithelial markers associated with HGSC. STR profiling using GenePrint 10 also revealed that injected FTE cells grown in vitro clustered with xenograft tumors of the same cell line, demonstrating that cell line and tumors retained the same characteristics during tumor development. It is hypothesized that SV40 alone is sufficient to stimulate genomic instability in the FTE cells. Several cell lines grown in culture with expression of hRASV12 demonstrated increased proliferation relative to normal control cells. Conclusions: Our results suggest that tumor development occurs at different rates in vivo and is dependent on multiple factors including genetic mutation, expression of oncogenes, and patient-derived characteristics. We demonstrated that cells grown in culture exhibit unstable chromosomal architecture characteristic of ovarian carcinomas, which is one of many potential factors that promotes neoplastic change in the tissue. Understanding how these factors act in promoting tumorigenesis will enable us to understand the molecular changes that occur in vivo prior to the development of ovarian serous carcinoma. Citation Format: Ramlogan Sowamber, Mauricio Medrano, Noor Salman, Zahra Maamir, Nick Chauvin, Mahmoud Bitar, Patricia Shaw, Sophia HL George. Differences in neoplastic transformation potential between OSE and FTE. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr B12.

Morphological and cytological analysis of yellow skin dragon fruit (Selenicereus megalanthus)

Abstract. Setyowati A, Sukaya, Yuniastuti E. 2018. Morphological and cytological analysis of yellow skin dragon fruit (Selenicereus megalanthus). Cell Biol Dev 2: 8-14. Dragon fruit is a tropical fruit that has the potential to be developed. Information on morphological and cytological characters of dragon fruit plants is still small and simple, so morphological and cytological analysis is necessary. The morphological and cytological analysis yielded useful information to support the dragon fruit plant breeding program. This study aims to study the morphological and cytological characteristics (karyotype) of the yellow skin dragon fruit (Selenicereus megalanthus (Schum. ex Vaupel) Moran). This study took samples from "Kusumo Wanadri Agrotourism" Glagah Indah Beach, Yogyakarta, Indonesia. Chromosomal identification was carried out at the Plant Breeding Laboratory, Faculty of Agriculture, Universitas Sebelas Maret, Indonesia. The research was carried out from December 2006 to June 2008. The methods used were field observations and treatment methods in water for 24 hours at a temperature of 5-8ºC, fixation in 45% acetic acid solution for 2 hours at a temperature of 5-8ºC, and hydrolysis in an aqueous solution. One (1) N HCl for 3-4 minutes at 60ºC, staining in 2% aceto-orcein solution for 24 hours at 5-8ºC and squashing. Morphological and cytological data were analyzed and presented descriptively. The morphology of the plant S. megalanthus is a white thread-shaped root with a fibrous plant root system. The stem is a smooth, faceted wet stem with concave edges. The fruit is oval, surrounded by short spines, the skin is yellow, and the flesh is white. The S. megalanthus has a tetraploid chromosome 2n = 4X = 44 with a chromosome length ranging from 2 + 0.098 m to 4.75 + 0.98 m. The karyotype formula for the S. megalanthus chromosome 2n = 4X = 44 = 40 m + 4 sm.

An assessment of the genetic integrity of micropropagated raspberry and blackberry plants

In vitro clonal propagation of small fruit species has been one of the most broadly exploited approaches in biotechnology. However, the most critical aspect of this propagation technology has been the maintenance of genetic fidelity of tissue culture-raised plants. In the present study, three techniques were deployed in the assessment of genetic fidelity of micropropagated plants (TC plants) of blackberry cultivar ‘Čačanska Bestrna’ and raspberry cultivar ‘Meeker’ in the second year after planting in the open field, in comparison to plants originating from the standard planting material (ST plants). Flow cytometry analysis deployed to estimate the DNA ploidy level and relative nuclear DNA content in TC and ST plants revealed no significant differences in nuclear DNA content between plants of different origin. Chromosome counting in root/shoot tip meristems also showed a normal tetraploid chromosome number (2n=4x=28) in TC blackberry plants and a normal diploid chromosome number (2n=2x=14) in TC raspberry plants. Polyacrylamide gel electrophoresis of peroxidase (POX) extracted from the leaf tissue revealed no differences in POX profiles between TC and ST plants either. The results obtained in this study verify the suitability of micropropagation by axillary branching for commercial exploitation in blackberry and raspberry.

Abstract 21: Ploidy Alteration of Murine Cardiac Progenitor Cells in Response to Infarction Injury

Introduction: Discovery of endogenous cardiac progenitor cells (CPC) prompted intense research efforts in multiple experimental animal models and clinical trials for heart failure treatment. Our lab identified a fundamental difference in ploidy content between rodent (rat, mouse) CPCs possessing mononuclear tetraploid (4n) chromosome content versus large mammal (human, swine) CPCs with mononuclear diploid (2n) content. Ploidy differences raise provocative questions regarding translational applicability of myocardial regeneration in rodents as polyplodization often correlates with enhanced regenerative potential. Hypothesis: Mononuclear chromatin duplication in CPCs improves regenerative capacity of the heart through higher stress resistance and overriding senescence cell-cycle arrest. Methods and Results: Ploidy of cultured CPCs is consistent and stable ploidy content over increased passages with samples from eight humans, two swine strains, six mouse strains, and seven rat clonal lines as determined by karyotype, confocal microscope and flow cytometry analyses. In situ ploidy analysis of CPCs reveals diploid content in human tissue and a mixture of mononuclear diploid and tetraploid nuclei in mouse, confirmed using freshly isolated Lin- c-kit+ CPCs. Tetraploid nuclear phenotype of murine CPCs is markedly different from predominantly diploid (2n) murine c-kit+ cells located in other tissues such as intestine and bone marrow. Higher ploidy content concurrent with expansion of the CPC pool are evident in the border zone at seven days post-infarction in adult FVB mice compared to age and gender matched non-injured hearts. Conclusion: Tetraploid c-kit+ cells found within the rodent heart may contribute to species-specific characteristics of stem cells and myocardial regenerative capacity. Future studies will focus upon the biological properties of diploid versus tetraploid CPCs and advantages of polyploid content for mediating myocardial regeneration.

Karyotype and Stomatal Studies on Three Genotypes of &lt;i&gt;Morus&lt;/i&gt; spp.

Three mulberry genotypes viz., MR2, C763 and Morus macroura were analyzed for the stomatal frequency and karyotypic attributes. MR2 and C763 were found to be diploids with somatic chromosome number of 2n=28, while variety Morus cathyana revealed tetraploid chromosome number of 2n=56. Somatic chromosomes measured 1.26 to 2.86µm in length. Karyotypes of these taxa are symmetric. Only metacentric and sub-metacentric chromosomes are found in the complement. Stomatal frequency was found to be high in diploid mulberry varieties compared to tetraploid variety. © 2017 The Japan Mendel Society.

Abstract 350: Chromosome Content of Cardiac Progenitor Cells Influence on Regenerative Potential in the Heart

Discovery of endogenous stem cells found within the heart, cardiac progenitor cells (CPC), has prompted intense basic discovery in multiple experimental animal models and clinical trials in heart failure patients. A survey of the literature reveals animal or cellular models exhibiting regenerative properties are also characterized by genome duplication or polyploidization. Our lab recently discovered a fundamental difference between large and small mammalian CPCs through karyotype analysis: rodent (rat, mouse) CPCs possess mononuclear tetraploid (4n) chromosome content, whereas large animal (human, swine) CPCs are mononuclear diploid (2n). This primary distinction between large and small animals prompts provocative questions regarding regenerative potential as well as the translational applicability of regenerative studies performed in rodent models. To expand on this finding, CPCs were isolated from eight human tissue samples (normal and heart failure), two swine strains (Gottingen and Yorkshire) six mice strains (FVB, C57, CAST, SPRET, SAMP6, and SAMR1), and seven rat clonal lines (Sprague Dawley), which confirmed karyotyped ploidy content per species as characterized through flow cytometry and confocal microscopy techniques. The large (human, swine) and small (rat, mouse) mammal CPCs maintained stable chromosome content through increased passaging and positive correlations appears between chromosome content and growth rate through increased passages as well as chromosome content and unrestrained growth through increased passages. The ploidy content of endogenous CPCs was investigated in situ with heart tissue sections with comparable ploidy determinations to that of cultured CPCs. Furthermore, the unique tetraploid content of murine CPCs is reinforced by comparison with ckit+ progenitor cells of secondary tissues (intestine and bone marrow) and cardiomyocytes in situ and in vitro that exhibit mostly diploid (2n) chromosome content per nuclei. These studies suggest ploidy may play a significant role in the biological capacity of the CPC and the endogenous stem cell pool may influence the regenerative capacity of the heart. Future directions will focus on defining the advantage of polyploid content in mediating regeneration.

Cytogenetic characterization of the Arabidopsis thaliana natural tetraploid ecotype Warschau stability during in vitro regeneration

The morphological and cytogenetic features of the natural autotetraploid Arabidopsis thaliana ecotype Warschau (Wa-1) were investigated. Most of the Warschau plant organs that were analyzed showed higher size values in comparison with diploid Columbia plants. The tetraploid chromosome number was confirmed by analysis of mitotic metaphase cells and rDNA loci were localized. 35S rDNA loci were present on chromosomes 2 and 4, while 5S rDNA, which is polymorphic among A. thaliana ecotypes, were present on chromosomes 4 and 5. Well-characterized autotetraploid plant material was used for in vitro culture to investigate somaclonal variation. Efficient regeneration through organogenesis was achieved. Most of the plants obtained in vitro exhibited an unchanged ploidy level. Detailed cytogenetic analysis that included chromosome, chromocenters and rDNA signals numbers, revealed the stability of regenerants. Based on these data we recommend the ecotype Warschau as a well-characterized plant material for future investigations on the consequences of polyploidy for the genome.

How diploidization turned a tetraploid into a pseudotriploid.

Despite being highly fertile and occupying a large geographic region, the North American heartleaf bittercress (Cardamine cordifolia; Brassicaceae) has a puzzling triploid-like chromosome number (2n = 3x = 24). As most triploids are sterile, we embarked on a detailed analysis of the C. cordifolia genome to elucidate its origin and structure. Mitotic and meiotic chromosome complement of C. cordifolia was analyzed by comparative chromosome painting using chromosome-specific BAC contigs of Arabidopsis thaliana. Resulting chromosome patterns were documented by multicolor fluorescence microscopy and compared with known ancestral and extant Brassicaceae genomes. We discovered that C. cordifolia is not a triploid hybrid but a diploidized tetraploid with the prevalence of regular, diploid-like meiotic pairing. The ancestral tetraploid chromosome number (2n = 32) was reduced to a triploid-like number (2n = 24) through four terminal chromosome translocations. The structure of the pseudotriploid C. cordifolia genome results from a stepwise diploidization process after whole-genome duplication. We showed that translocation-based descending dysploidy (from n = 16 to n = 12) was mediated by the formation of five new chromosomes. The genome of C. cordifolia represents the diploidization process in statu nascendi and provides valuable insights into mechanisms of postpolyploidy rediploidization in land plants. Our data further suggest that chromosome number alone does not need to be a reliable proxy of species' evolutionary past and that the same chromosome number may originate either by polyploidization (hybridization) or due to descending dysploidy.

Molecular and cytogenetic evidence for an allotetraploid origin of Chenopodium quinoa and C. berlandieri (Amaranthaceae)

Most of the cultivated chenopods are polyploids, but their origin and evolutionary history are still poorly understood. Phylogenetic analyses of DNA sequences of four plastid regions, nrITS and nuclear 5S rDNA spacer region (NTS) of two tetraploid chenopods (2n=4x=36), Andean C. quinoa and North American C. berlandieri, and their diploid relatives allowed inferences of their origin. The phylogenetic analyses confirmed allotetraploid origin of both tetraploids involving diploids of two different genomic groups (genomes A and B) and suggested that these two might share very similar parentage.The hypotheses on the origin of the two allopolyploid species were further tested using genomic in situ hybridization (GISH). Several diploid Chenopodium species belonging to the two lineages, genome A and B, suggested by phylogenetic analyses, were tested as putative parental taxa. GISH differentiated two sets of parental chromosomes in both tetraploids and further corroborated their allotetraploid origin. Putative diploid parental taxa have been suggested by GISH for C. quinoa and C. berlandieri. Genome sizes of the analyzed allotetraploids fit nearly perfectly the expected additive values of the putative parental taxa. Directional and uniparental loss of rDNA loci of the maternal A-subgenome was revealed for both C. berlandieri and C. quinoa.

Segmental paleotetraploidy revealed in sterlet (Acipenser ruthenus) genome by chromosome painting.

BackgroundAcipenseriformes take a basal position among Actinopteri and demonstrate a striking ploidy variation among species. The sterlet (Acipenser ruthenus, Linnaeus, 1758; ARUT) is a diploid 120-chromosomal sturgeon distributed in Eurasian rivers from Danube to Enisey. Despite a high commercial value and a rapid population decline in the wild, many genomic characteristics of sterlet (as well as many other sturgeon species) have not been studied.ResultsCell lines from different tissues of 12 sterlet specimens from Siberian populations were established following an optimized protocol. Conventional cytogenetic studies supplemented with molecular cytogenetic investigations on obtained fibroblast cell lines allowed a detailed description of sterlet karyotype and a precise localization of 18S/28S and 5S ribosomal clusters. Localization of sturgeon specific HindIII repetitive elements revealed an increased concentration in the pericentromeric region of the acrocentric ARUT14, while the total sterlet repetitive DNA fraction (C0t30) produced bright signals on subtelomeric segments of small chromosomal elements. Chromosome and region specific probes ARUT1p, 5, 6, 7, 8 as well as 14 anonymous small sized chromosomes (probes A-N) generated by microdissection were applied in chromosome painting experiments. According to hybridization patterns all painting probes were classified into two major groups: the first group (ARUT5, 6, 8 as well as microchromosome specific probes C, E, F, G, H, and I) painted only a single region each on sterlet metaphases, while probes of the second group (ARUT1p, 7 as well as microchromosome derived probes A, B, D, J, K, M, and N) marked two genomic segments each on different chromosomes. Similar results were obtained on male and female metaphases.ConclusionsThe sterlet genome represents a complex mosaic structure and consists of diploid and tetraploid chromosome segments. This may be regarded as a transition stage from paleotetraploid (functional diploid) to diploid genome condition. Molecular cytogenetic and genomic studies of other 120- and 240-chromosomal sturgeons are needed to reconstruct genome evolution of this vertebrate group.

Abstract 18976: Progenitor Cell Ploidy: The Regulator of Regenerative Fate

Cellular therapy is an emerging interventional strategy to treat heart failure and has demonstrated tremendous potential in recent years. Use of endogenous stem cells found within the heart, cardiac progenitor cells (CPC), has prompted intense basic research in multiple experimental animal models as well as clinical trials in heart failure patients. Scientifically, the field continues to unravel mechanisms of CPC involvement in remodeling and repair of the heart under both normal and pathologic conditions. Research has been primarily performed in mouse models, which represent the fundamental experimental platform for a vast array of regenerative medicine research. Given the importance of mouse models for stem cell research, understanding fundamental differences between mouse and human stem cell biology are essential. Our findings show that adult murine CPCs contain tetraploid (4n) chromosome content in contrast to the normally expected diploid (2n) chromosome content as found in human CPCs by karyotype analyses. To expand the significance of this finding, CPCs were isolated from standard lab mice (FVB and C57), human telomere-length equivalent mice (CAST and SPRET) and an early onset senescence mouse (SAMP6), which revealed mononuclear tetraploid content as characterized through a combination of flow cytometry and confocal microscopy analysis using antibodies and fluorescence in situ hybridization (FISH) techniques. In comparison, isolated murine ckit+ bone marrow stem cells possess mononuclear diploid content through similar analysis. The ploidy content of endogenous murine and human CPCs was investigated in situ with heart tissue sections with comparable ploidy determinations to that of cultured CPCs. Furthermore, the unique tetraploid content of CPCs within the murine heart is reinforced by comparison with ckit+ progenitor cells of secondary tissues (intestine and bone) that exhibit diploid chromosome content. These studies reveal a fundamental difference between human and murine CPCs that is essential for functional regenerative potential since regenerative tissues commonly are polyploid. Future directions will focus on defining the advantage of polyploidy in mediating regeneration.

Comparative Life Cycle Transcriptomics Revises Leishmania mexicana Genome Annotation and Links a Chromosome Duplication with Parasitism of Vertebrates.

Leishmania spp. are protozoan parasites that have two principal life cycle stages: the motile promastigote forms that live in the alimentary tract of the sandfly and the amastigote forms, which are adapted to survive and replicate in the harsh conditions of the phagolysosome of mammalian macrophages. Here, we used Illumina sequencing of poly-A selected RNA to characterise and compare the transcriptomes of L. mexicana promastigotes, axenic amastigotes and intracellular amastigotes. These data allowed the production of the first transcriptome evidence-based annotation of gene models for this species, including genome-wide mapping of trans-splice sites and poly-A addition sites. The revised genome annotation encompassed 9,169 protein-coding genes including 936 novel genes as well as modifications to previously existing gene models. Comparative analysis of gene expression across promastigote and amastigote forms revealed that 3,832 genes are differentially expressed between promastigotes and intracellular amastigotes. A large proportion of genes that were downregulated during differentiation to amastigotes were associated with the function of the motile flagellum. In contrast, those genes that were upregulated included cell surface proteins, transporters, peptidases and many uncharacterized genes, including 293 of the 936 novel genes. Genome-wide distribution analysis of the differentially expressed genes revealed that the tetraploid chromosome 30 is highly enriched for genes that were upregulated in amastigotes, providing the first evidence of a link between this whole chromosome duplication event and adaptation to the vertebrate host in this group. Peptide evidence for 42 proteins encoded by novel transcripts supports the idea of an as yet uncharacterised set of small proteins in Leishmania spp. with possible implications for host-pathogen interactions.

Chromosome doubling in Paspalum notatum var. saure (cultivar Pensacola)

Paspalum notatum is one of the most important native grassland species of southern Brazil, and the main forage source for livestock. The native ecotypes are tetraploid and have apomictic reproduction, which prevents the registration and protection of plant varieties. However, the cultivated variety Paspalum notatum var. saurae (cultivar Pensacola) is diploid and sexual. The objective of this study was to artificially produce polyploid cv. Pensacola plants, to be used as female parents in crosses with male tetraploid and apomictic parents. Seedlings and seeds were immersed in colchicine solutions for different periods. A tetraploid chromosome number was confirmed in three plants. The reproduction mode of the resulting polyploid plants will be assessed; if confirmed to be sexual, they can be used in crosses with native apomictic plants to breed new intraspecific hybrids.

&lt;p&gt;&lt;strong&gt;&lt;em&gt;Allium occultum,&lt;/em&gt; a new species of &lt;em&gt;A.&lt;/em&gt; sect. &lt;em&gt;Codonoprasum&lt;/em&gt; (Amaryllidaceae) from Skiros Island (W Aegean, Greece)&lt;/strong&gt;&lt;/p&gt;

Allium occultum Tzanoudakis &amp; Trigas sp. nov. (Amaryllidaceae) from Skiros Island (W Aegean, Greece) is described and illustrated. It belongs to A. sect. Codonoprasum and more precisely to A. paniculatum group. Its closest relatives seem to be A. apergii and A. dirphianum, both endemic to Euboea Island (W Aegean). The new species is currently known from two neighbouring localities of Mt. Kochilas. The tetraploid chromosome number (2n = 32) was found in plants from both localities and according to the karyotype structure, the new species seems functionally diploid.

Allium occultum, a new species of A. sect. Codonoprasum (Amaryllidaceae) from Skiros Island (W Aegean, Greece)

Allium occultum Tzanoudakis &amp; Trigas sp. nov. (Amaryllidaceae) from Skiros Island (W Aegean, Greece) is described and illustrated. It belongs to A. sect. Codonoprasum and more precisely to A. paniculatum group. Its closest relatives seem to be A. apergii and A. dirphianum, both endemic to Euboea Island (W Aegean). The new species is currently known from two neighbouring localities of Mt. Kochilas. The tetraploid chromosome number (2n = 32) was found in plants from both localities and according to the karyotype structure, the new species seems functionally diploid.