No abstract

Ageing is a phenomenon where the accumulation of all the stresses that alter the functions of living organisms, halter them from maintaining their physiological balance and eventually lead to death. The emergence of epigenetic tremendously contributed to the knowledge of ageing. Epigenetic changes in cells or tissues like deoxyribonucleic acid (DNA) methylation, modification of histone proteins, transcriptional modification and also the involvement of non-coding DNA has been documented to be associated with ageing. In order to study ageing, scientists have taken advantage of several potential organisms to aid them in their study. Drosophila melanogaster has been an essential model in establishing current understanding of the mechanism of ageing as they possess several advantages over other competitors like having homologues to more than 75% of human disease genes, having 50% of Drosophila genes are homologues to human genes and most importantly they are genetically amenable. Here, we would like to summarise the extant knowledge about ageing and epigenetic process and the role of Drosophila as an ideal model to study epigenetics in association with ageing process.

Rhodotorula sp. (USM-PSY62) is a psychrophilic yeast isolated from Antarctic sea ice and it grows optimally at 15 °C. This study was set up to observe how USM-PSY62 adapted to fluctuations in temperature. During cold adaptation, an elevated transcription of the CorA magnesium transporter gene in USM-PSY62 indicated a higher requirement for magnesium ions in order to gain additional enzyme cofactors or maintain cytoplasmic fluidity. The HepA homologue coding for DNA/RNA helicase was also over-expressed in cold condition possibly to reorganize secondary structures of DNA and RNA. An up-regulation of the catalase gene was also observed reflecting an increment in the concentration of reactive oxygen species and fluctuations in the associated antioxidant system. The YOP1 gene, which encodes a membrane protein associated with protein transport and membrane traffic, was the most down-regulated under cold shock condition. The genes responsible for the structural maintenance of chromosome (SMC) were also down-regulated when the temperature was shifted to 0 ⁰C. Upon cold shock, the gene for heat shock factor protein 1 (HSF1) was also down-regulated. Hsf1 is a transcriptional regulator which regulate the heat shock responses. Although USM-PSY62 showed some common adaptive strategies as in several other psychrophilic organisms, new mechanisms were also uncovered.