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Diploid Organisms (diploid + organism)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Chromosome instability in Candida albicans

FEMS YEAST RESEARCH, Issue 1 2007
Elena Rustchenko
Abstract Candida albicans maintains genetic diversity by random chromosome alterations, and this diversity allows utilization of various nutrients. Although the alterations seem to occur spontaneously, their frequencies clearly depend on environmental factors. In addition, this microorganism survives in adverse environments, which cause lethality or inhibit growth, by altering specific chromosomes. A reversible loss or gain of one homolog of a specific chromosome in this diploid organism was found to be a prevalent means of adaptation. We found that loss of an entire chromosome is required because it carries multiple functionally redundant negative regulatory genes. The unusual mode of gene regulation in Candida albicans implies that genes in this organism are distributed nonrandomly over chromosomes. [source]

Polyploidy-Associated Genomic Instability in Arabidopsis thaliana

GENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 4 2010
Yixing Wang
Formation of polyploid organisms by fertilization of unreduced gametes in meiotic mutants is believed to be a common phenomenon in species evolution. However, not well understood is how species in nature generally exist as haploid and diploid organisms in a long evolutionary time while polyploidization must have repeatedly occurred via meiotic mutations. Here, we show that the ploidy increased for two consecutive generations due to unreduced but viable gametes in the Arabidopsis cyclin a1;2-2 (also named tardy asynchronousmeiosis-2) mutant, but the resultant octaploid plants produced progeny of either the same or reduced ploidy via genomic reductions during meiosis and pollen mitosis. Ploidy reductions through sexual reproduction were also observed in independently generated artificial octaploid and hexaploid Arabidopsis plants. These results demonstrate that octaploid is likely the maximal ploidy produced through sexual reproduction in Arabidopsis. The polyploidy-associated genomic instability may be a general phenomenon that constrains ploidy levels in species evolution. [source]

A simple method for the calculation of microsatellite genotype distances irrespective of ploidy level

MOLECULAR ECOLOGY, Issue 7 2004
ICA BRUVO
Abstract Microsatellites are powerful molecular markers, used commonly to estimate intraspecific genetic distances. With the exception of band sharing similarity index, available distance measures were developed specifically for diploid organisms and are unsuited for comparisons of polyploids. Here, we present a simple method for calculation of microsatellite genotype distances, which takes into account mutation processes and permits comparison of individuals with different ploidy levels. This method should provide a valuable tool for intraspecific analyses of polyploid organisms, which are widespread among plants and some animal taxa. An illustration is given using data from the planarian flatworm Schmidtea polychroa (Platyhelminthes). [source]

The ,-1,3-glucanosyltransferase gas4p is essential for ascospore wall maturation and spore viability in Schizosaccharomyces pombe

MOLECULAR MICROBIOLOGY, Issue 5 2008
Marķa De Medina-Redondo
Summary Meiosis is the developmental programme by which sexually reproducing diploid organisms generate haploid gametes. In yeast, meiosis is followed by spore morphogenesis. The formation of the Schizosaccharomyces pombe ascospore wall requires the co-ordinated activity of enzymes involved in the biosynthesis and modification of its components, such as glucans. During sporogenesis, the ,-1,3-glucan synthase bgs2p synthesizes linear ,-1,3-glucans, which remain unorganized and alkali-soluble until covalent linkages are set up between ,-1,3-glucans and other cell wall components. Several proteins belonging to the glycoside hydrolase family 72 (GH72) with ,-1,3-glucanosyltransferase activity have been described in other organisms, such as the Saccharomyces cerevisiae Gas1p or the Aspergillus fumigatus Gel1p. Here we describe the characterization of gas4+, a new gene that encodes a protein of the GH72 family. Deletion of this gene does not lead to any apparent defect during vegetative growth, but homozygous gas4, diploids show a sporulation defect. Although meiosis occurs normally, ascospores are unable to mature or to germinate. The expression of gas4+ is strongly induced during sporulation and a yellow fluorescent protein (YFP),gas4p fusion protein localizes to the ascospore periphery during sporulation. We conclude that gas4p is required for ascospore maturation in S. pombe. [source]

Topoisomerase II may be linked to the reduction of chromosome number in meiosis

BIOESSAYS, Issue 4 2003
Leocadia V. Paliulis
A reduction of chromosome number in meiosis is essential for genome transmission in diploid organisms. Reduction depends on a change in kinetochore configuration.1 A recent study2 connects changes in kinetochores with other changes in chromosome structure and raises the intriguing possibility that topoisomerase II, the DNA untangling enzyme, is involved. BioEssays 25:309,312, 2003. © 2003 Wiley Periodicals, Inc. [source]