The role of SYN1 in early Arabidopsis meiosis

SYN1 is a meiosis-specific Arabidopsis homologue of yeast REC8. REC8 is an important component of the meiotic cohesion complex which maintains cohesion between sister chromatids. Cytological analysis of syn1$^{-/-}$ has shown chromosome fragmentation at metaphase I. To determine the basis of chromosome fragmentation in the syn1$^{-/-}$, three double mutants were constructed. I have demonstrated that chromosome fragmentation in syn1 is AtSPO11-1-dependent. Moreover, I have also shown that SYN1 has a role in DSB repair by analysing Atdmc1$^{-/-}$/syn1$^{-/-}$ meiocytes. To investigate this further, immunolocalization studies in wild-type and syn1$^{-/-}$ were conducted. Distribution of ASY1 and AtZYP1 was affected in syn1$^{-/-}$. Both proteins appeared as aggregates, developing into an abnormal short linear signal in early prophase I, suggesting that both axis formation and synapsis are compromised. Distribution of the recombination proteins AtRAD51 and AtMLH1 was also aberrant. Localization of SYN1 in wild-type nuclei revealed a continuous signal along the chromosome axes. However, careful inspection revealed that this was accompanied by patches of more intense signals, possibly corresponding to DSB regions. To investigate this further I analysed SYN1 distribution in an Atspo11-1-4$^{-/-}$ mutant. Whilst faint SYN1 signals were apparent along the axis, no patches of intense signals were visible. Cisplatin-induced DSBs restored AtZYP1 foci in Atspo11-1-4$^{-/-}$ and also resulted in restoration of intense patches of the SYN1 signals. This is consistent with the recruitment of SYN1 to DSB sites

Chromosome segregation in plant meiosis

Faithful chromosome segregation in meiosis is essential for ploidy stability over sexual life cycles. In plants, defective chromosome segregation caused by gene mutations or other factors leads to the formation of unbalanced or unreduced gametes creating aneuploid or polyploid progeny, respectively. Accurate segregation requires the coordinated execution of conserved processes occurring throughout the two meiotic cell divisions. Synapsis and recombination ensure the establishment of chiasmata that hold homologous chromosomes together allowing their correct segregation in the first meiotic division, which is also tightly regulated by cell-cycle dependent release of cohesin and monopolar attachment of sister kinetochores to microtubules. In meiosis II, bi-orientation of sister kinetochores and proper spindle orientation correctly segregate chromosomes in four haploid cells. Checkpoint mechanisms acting at kinetochores control the accuracy of kinetochore-microtubule attachment, thus ensuring the completion of segregation. Here we review the current knowledge on the processes taking place during chromosome segregation in plant meiosis, focusing on the characterization of the molecular factors involved

Singapore office and private residential property market : an industry and company analysis

The motivation for this research project stems from interest in (1) ,the rapid development of the local office property market buoyant about the growth in the financial and business sectors and, (2) the recent boom in the private residential property sector. This research is carried out with the objectives of assessing the outlook for the office and private residential property markets in Singapore ( through an industry analysis) and their impacts on selected property companies (through a company analysis). Our industry analysis revealed that the office property market in Singapore is currently experiencing a boom which is likely to persist until 1998. This is due to limited new office space supply in the near to medium term and strong demand driven by favourable economic fundamentals in Singapore as well as Southeast Asian region. On the other hand, the outlook of the private residential property market is mixed, depending on the type and locality of the properties concerned. Supply, though huge, is expected to be met by the demand for private housing. Prices for related categories, such as those with freehold or 999-year tenure and prime locations, are likely to increase while others are expected to be mo~e affordable in the near future. Our company analysis revealed that Straits Steamship Land and Singapore Land Limited are strong office property market players while Malayan Credit Limited and First Capital Corporation are highly exposed to the private residential property sector. City Development Land is active in both sectors. In addition. Straits Steamship Land and City Development Land are expected to outperform the rest in the future in view of their overall exposure to the local property market and their regionalisation drive.ACCOUNTANC

Chromosome segregation in plant meiosis

Faithful chromosome segregation in meiosis is essential for ploidy stability over sexual life cycles. In plants, defective chromosome segregation caused by gene mutations or other factors leads to the formation of unbalanced or unreduced gametes creating aneuploid or polyploid progeny, respectively. Accurate segregation requires the coordinated execution of conserved processes occurring throughout the two meiotic cell divisions. Synapsis and recombination ensure the establishment of chiasmata that hold homologous chromosomes together allowing their correct segregation in the first meiotic division, which is also tightly regulated by cell-cycle dependent release of cohesin and monopolar attachment of sister kinetochores to microtubules. In meiosis II, bi-orientation of sister kinetochores and proper spindle orientation correctly segregate chromosomes in four haploid cells. Checkpoint mechanisms acting at kinetochores control the accuracy of kinetochore-microtubule attachment, thus ensuring the completion of segregation. Here we review the current knowledge on the processes taking place during chromosome segregation in plant meiosis, focusing on the characterization of the molecular factors involved.status: publishe

Large-Scale Whole-Genome Sequencing of Three Diverse Asian Populations in Singapore

Because of Singapore's unique history of immigration, whole-genome sequence analysis of 4,810 Singaporeans provides a snapshot of the genetic diversity across East, Southeast, and South Asia.</p