Quercitol and osmotic adaptation of field-grown Eucalyptus under seasonal drought stress

This study investigated the role of quercitol in osmotic adjustment in field-grown Eucalyptus astringens Maiden subject to seasonal drought stress over the course of 1 year. The trees grew in a native woodland and a farm plantation in the semi-arid wheatbelt region of south Western Australia. Plantation trees allocated relatively more biomass to leaves than woodland trees, but they suffered greater drought stress over summer, as indicated by lower water potentials, CO₂ assimilation rates and stomatal conductances. In contrast, woodland trees had relatively fewer leaves and suffered less drought stress. Plantation trees under drought stress engaged in osmotic adjustment, but woodland trees did not. Quercitol made a significant contribution to osmotic adjustment in drought-stressed trees (25% of total solutes), and substantially more quercitol was measured in the leaves of plantation trees (5% dry matter) than in the leaves of woodland trees (2% dry matter). We found no evidence that quercitol was used as a carbon storage compound while starch reserves were depleted under drought stress. Differences in stomatal conductance, biomass allocation and quercitol production clearly indicate that E. astringens is both morphologically and physiologically 'plastic' in response to growth environment, and that osmotic adjustment is only one part of a complex strategy employed by this species to tolerate drought.     

Activation of NK cell-mediated cytotoxicity by a SAP-independent receptor of the CD2 family.

Some CD2 family receptors stimulate NK cell-mediated cytotoxicity through a signaling pathway, which is dependent on the recruitment of an adapter protein called SLAM-associated protein (SAP). In this work we identify a novel leukocyte cell surface receptor of the CD2 family called CD2-like receptor activating cytotoxic cells (CRACC). CRACC is expressed on cytotoxic lymphocytes, activated B cells, and mature dendritic cells, and activates NK cell-mediated cytotoxicity. Remarkably, although CRACC displays cytoplasmic motifs similar to those recruiting SAP, CRACC-mediated cytotoxicity occurs in the absence of SAP and requires activation of extracellular signal-regulated kinases-1/2. Thus, CRACC is a unique CD2-like receptor which mediates NK cell activation through a SAP-independent extracellular signal-regulated kinase-mediated pathway.     

Precursor cystatin C in cultured retinal pigment epithelium cells: evidence for processing through the secretory pathway.

Evidence was recently reported that the cysteine proteinase inhibitor, cystatin C, is highly expressed by cultured human retinal pigment epithelial (RPE) cells. As a step towards understanding possible functions of this protein associated with the RPE, the localization, targetting and trafficking of cystatin C were investigated. Constructs encoding an enhanced variant of green fluorescent protein (EGFP) fused to precursor cystatin C and to mature cystatin C were made and transfected into cultured human RPE cells. Expression of fusion proteins was monitored in vivo by fluorescence confocal microscopy. In cells transfected with precursor cystatin C-EGFP, fluorescence was initially targetted to the perinuclear zone, co-localizing with the Golgi apparatus. Transfected cells were observed at intervals over a period of up to 3 weeks, during which time fluorescent vesicles developed peripherally and basally while fluorescence continued to be detected in the Golgi region. Immunochemical analysis of cell lysates confirmed the expression of a fusion protein recognized by antibodies to both cystatin C and EGFP. Cells transfected with the construct lacking the leader peptide of precursor cystatin C presented a diffuse and weak fluorescence. Together, these results imply a leader sequence-dependent processing of cystatin C through the secretory pathway of RPE cells. This was confirmed by the detection, by Western blotting, of the chimaeric protein alongside endogenous cystatin C in the medium of transfected RPE cells.     

The Role of <Emphasis Type="Italic">Habitus</Emphasis> in the Maintenance of Traditional Noongar Plant Knowledge in Southwest Western Australia

We examine the role that habitus, an individual’s or group’s dispositions, has played in the retention of traditional ecological knowledge among the Noongar people of south-western Australia. We sought to determine if current plant knowledge reflects Noongar habitus or, alternatively, the use of fall-back species that were important due to the intermittency of agricultural employment and the social exclusion of Aboriginal people up until at least the 1960s in Western Australia. We compared the seasonal availability of Noongar food plant resources currently known by Noongar Elders to those described at the time of European settlement. We used non-metric Multidimensional Scaling (nMDS) and multivariate statistics to compare the seasonal availability of plant resources with the seasonal availability of work prior to the introduction of civil rights for Aboriginal Australians in the 1960s. We show that the seasonal pattern of plant knowledge has changed little since settlement and that there was no significant relationship between the seasonal availability of work and plant knowledge. This result suggests that prior to 1960 Noongars maintained a reasonably traditional round of seasonal activities involving traditional plant use. We suggest that Noongar habitus guided their response to the colonising culture and helped preserve traditional ecological knowledge.