Comparative post-fire water relations of selected reseeding and resprouting fynbos plants in the Jonkershoek Valley, Cape Province, South Africa

Leaf area development has been proposed as a simple predictor of post-fire streamflow response in the mountain catchments of the south-western Cape, South Africa. Implicit in this proposal is the assumption that transpiration rates per unit leaf area of reseeders and resprouters are similar. This assumption was tested by studying the water relations of selected fynbos plants after a fire in a mountain catchment in the Jonkershoek Valley near Stellenbosch for nearly two years. Stomatal conductances and xylem pressure potentials were measured and transpiration rates were estimated for three reseeding species and four resprouting species. There was no clear difference between the daily transpiration rates of reseeding and resprouting plants. The shallow-rooted resprouters responded similarly to the reseeders; moderate water stress (−3 to −4MPa) and reduced transpiration (<1mmolm−2 s−1) were experienced during the first two summers after fire. The deep-rooted resprouters did not show water stress during summer, and transpiration rates were moderate throughout the year. Annual patterns of water use per unit leaf area were similar for reseeders and resprouters. Leaf area may therefore be used as a simple predictor of post-fire streamflow response

The cataract and glucosuria associated monocarboxylate transporter MCT12 is a new creatine transporter

Creatine transport has been assigned to creatine transporter 1 (CRT1), encoded by mental retardation associated SLC6A8. Here, we identified a second creatine transporter (CRT2) known as monocarboxylate transporter 12 (MCT12), encoded by the cataract and glucosuria associated gene SLC16A12. A non-synonymous alteration in MCT12 (p.G407S) found in a patient with age-related cataract (ARC) leads to a significant reduction of creatine transport. Furthermore, Slc16a12 knockout (KO) rats have elevated creatine levels in urine. Transport activity and expression characteristics of the two creatine transporters are distinct. CRT2 (MCT12)-mediated uptake of creatine was not sensitive to sodium and chloride ions or creatine biosynthesis precursors, breakdown product creatinine or creatine phosphate. Increasing pH correlated with increased creatine uptake. Michaelis-Menten kinetics yielded a Vmax of 838.8 pmol/h/oocyte and a Km of 567.4 µm. Relative expression in various human tissues supports the distinct mutation-associated phenotypes of the two transporters. SLC6A8 was predominantly found in brain, heart and muscle, while SLC16A12 was more abundant in kidney and retina. In the lens, the two transcripts were found at comparable levels. We discuss the distinct, but possibly synergistic functions of the two creatine transporters. Our findings infer potential preventive power of creatine supplementation against the most prominent age-related vision impaired conditio

Cell fate regulation by chromatin ADP-ribosylation

ADP-ribosylation is an evolutionarily conserved complex posttranslational modification that alters protein function and/or interaction. Intracellularly, it is mainly catalyzed by diphtheria toxin-like ADP-ribosyltransferases (ARTDs), which attach one or several ADP-ribose residues onto target proteins. Several specific mono- and poly-ADP-ribosylation binding modules exist; hydrolases reverse the modification. The best-characterized ARTD family member, ARTD1, regulates various DNA-associated processes. Here, we focus on the role of ARTD1-mediated chromatin ADP-ribosylation in development, differentiation, and pluripotency, and the recent development of new methodologies that will enable more insight into these processes

Low levels of glutathione are sufficient for survival of keratinocytes after UV irradiation and for healing of mouse skin wounds

Reduced levels of the cellular antioxidant glutathione are associated with premature skin aging, cancer and impaired wound healing, but the in vivo functions of glutathione in the skin remain largely unknown. Therefore, we analyzed mice lacking the modifier subunit of the glutamate cysteine ligase (Gclm), the enzyme that catalyzes the rate-limiting step of glutathione biosynthesis. Glutathione levels in the skin of these mice were reduced by 70 %. However, neither skin development and homeostasis, nor UVA- or UVB-induced apoptosis in the epidermis were affected. Histomorphometric analysis of excisional wounds did not reveal wound healing abnormalities in young Gclm-deficient mice, while the area of hyperproliferative epithelium as well as keratinocyte proliferation were affected in aged mice. These findings suggest that low levels of glutathione are sufficient for wound repair in young mice, but become rate-limiting upon aging.ISSN:0340-3696ISSN:1432-069

New quantitative mass spectrometry approaches reveal different ADP-ribosylation phases dependent on the levels of oxidative stress

Oxidative stress is a potent inducer of protein ADP-ribosylation. Although individual oxidative stress-induced ADP-ribosylated proteins have been identified, it is so far not clear to which extent different degrees of stress severity quantitatively and qualitatively alter ADP-ribosylation. Here, we investigated both quantitative and qualitative changes of the hydrogen peroxide (H2O2)-induced ADP-ribosylome using a label-free shotgun quantification and a parallel reaction monitoring (PRM) mass spectrometry approach for a selected number of identified ADP-ribosylated peptides. Although the major part of the basal HeLa ADP-ribosylome remained unchanged upon all tested H2O2 concentrations, some selected peptides change the extent of ADP-ribosylation depending on the degree of the applied oxidative stress. Low oxidative stress (i.e. 4 μm and 16 μm H2O2) caused a reduction in ADP-ribosylation of modified proteins detected under untreated conditions. In contrast, mid to strong oxidative stress (62 μm to 1 mm H2O2) induced a significant increase in ADP-ribosylation of oxidative stress-targeted proteins. The application of the PRM approach to SKOV3 and A2780, ovarian cancer cells displaying different sensitivities to PARP inhibitors, revealed that the basal and the H2O2-induced ADP-ribosylomes of SKOV3 and A2780 differed significantly and that the sensitivity to PARP inhibitors correlated with the level of ARTD1 expression in these cells. Overall, this new PRM-MS approach has proven to be sensitive in monitoring alterations of the ADP-ribosylome and has revealed unexpected alterations in proteins ADP-ribosylation depending on the degree of oxidative stress

The cataract and Glucosuria associated monocarboxylate transporter MCT12 is a new creatine transporter

Creatine transport has been assigned to creatine transporter 1 (CRT1), encoded by mental retardation associated SLC6A8. Here, we identified a second creatine transporter (CRT2) known as monocarboxylate transporter 12 (MCT12), encoded by the cataract and glucosuria associated gene SLC16A12. A non-synonymous alteration in MCT12 (p.G407S) found in a patient with age-related cataract (ARC) leads to a significant reduction of creatine transport. Furthermore, Slc16a12 knockout (KO) rats have elevated creatine levels in urine. Transport activity and expression characteristics of the two creatine transporters are distinct. CRT2 (MCT12)-mediated uptake of creatine was not sensitive to sodium and chloride ions or creatine biosynthesis precursors, breakdown product creatinine or creatine phosphate. Increasing pH correlated with increased creatine uptake. Michaelis-Menten kinetics yielded a Vmax of 838.8 pmol/h/oocyte and a Km of 567.4 µm. Relative expression in various human tissues supports the distinct mutation-associated phenotypes of the two transporters. SLC6A8 was predominantly found in brain, heart and muscle, while SLC16A12 was more abundant in kidney and retina. In the lens, the two transcripts were found at comparable levels. We discuss the distinct, but possibly synergistic functions of the two creatine transporters. Our findings infer potential preventive power of creatine supplementation against the most prominent age-related vision impaired condition