ALMA observations of the variable 12CO/13CO ratio around the asymptotic giant branch star R Sculptoris

[abridged] The 12CO/13CO ratio is often used as a measure of the 12C/13C ratio in the circumstellar environment, carrying important information about the stellar nucleosynthesis. External processes can change the 12CO and 13CO abundances, and spatially resolved studies of the 12CO/13CO ratio are needed to quantify the effect of these processes on the globally determined values. Additionally, such studies provide important information on the conditions in the circumstellar environment. The detached-shell source R Scl, displaying CO emission from recent mass loss, in a binary-induced spiral structure as well as in a clumpy shell produced during a thermal pulse, provides a unique laboratory for studying the differences in CO isotope abundances throughout its recent evolution. We observed both the 12CO(J=3-2) and the 13CO(J=3-2) line using ALMA. We find significant variations in the 12CO/13CO intensity ratios and consequently in the abundance ratios. The average CO isotope abundance ratio is at least a factor three lower in the shell (~19) than that in the present-day (60). Additionally, variations in the ratio of more than an order of magnitude are found in the shell itself. We attribute these variations to the competition between selective dissociation and isotope fractionation in the shell, of which large parts cannot be warmer than ~35 K. However, we also find that the 12CO/13CO ratio in the present-day mass loss is significantly higher than the 12C/13C ratio determined in the stellar photosphere from molecular tracers (~19). The origin of this discrepancy is still unclear, but we speculate that it is due to an embedded source of UV-radiation that is primarily photo-dissociating 13CO. This radiation source could be the hitherto hidden companion. Alternatively, the UV-radiation could originate from an active chromosphere of R Scl itself....Comment: 6 pages, 5 figures, online data available at http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=J/A+A/556/L

Cloning of Phenylalanine ammonia-lyase (PAL) gene fragment from Aquilaria malaccensis Lam. (karas).

Current practice of indiscriminate and illegal felling of 'karas' trees (Aquilaria malaccensis) to extract 'gaharu' in the wild have caused the population to dwindle drastically. 'Gaharu' formed as a result of natural defense mechanism in trees, which unfortunately happens over a long period of time. To better understand natural processes of gaharu-making, we sought to study the roles of defense genes in 'karas' by cloning a gene that synthesizes secondary compounds. The phenylalanine ammonia-lyase (PAL) gene encodes an enzyme in the metabolism of phenylpropanoid compounds, which are produced in response to stress, such as damage by wounding and pathogen attack. We report a cloned PAL gene fragment from A. malaccensis using the polymerase chain reaction (PCR) technique. The fragment was amplified from genomic DNA of a wounded 2-year old tree and cloned into the pGEM-T Easy Vector. The cloned fragment had a length of 610bp and an uninterrupted open reading frame of 201 amino acids. When searched against the Genebank database using BLAST tools, the cloned fragment shared 92% sequence similarity at amino acid level to known PAL proteins. This work will serve as a foundation in identifying important genes for triggering 'gaharu' synthesis