Legumes mitigate ecological consequences of a topographic gradient in a northern Mongolian steppe

Topography should create spatial variation in water and nutrients and play an especially important role in the ecology of water-limited systems. We use stable isotopes to discern how plants respond both to ecological gradients associated with elevation and to neighboring legumes on a south-facing slope in the semi-arid, historically grazed steppe of northern Mongolia. Out of three target species, Potentilla acaulis, Potentilla sericea, and Festuca lenensis, when >30 cm from a legume, all showed a decrease in leaf δ¹⁵N with increasing elevation. This, together with measures of soil δ¹⁵N, suggests greater N processing at the moister, more productive, lower elevation, and more N fixation at the upper elevation, where cover of legumes and lichens and plant-available nitrate were greater. Total soil N was greater at the lower elevation, but not lichen biomass or root colonization by AMF. Leaf δ¹³C values for P. acaulis and F. lenensis are consistent with increasing water stress with elevation; δ¹³C values indicated the greatest intrinsic water use efficiency for P. sericea, which is more abundant at the upper elevation. Nearby legumes (<10 cm) moderate the effect of elevation on leaf δ¹⁵N, confirming legumes’ meaningful input of N, and affect leaf δ¹³C for two species, suggesting an influence on the efficiency of carbon fixation. Variation in leaf %N and %C as a function of elevation and proximity to a legume differs among species. Apparently, most N input is at upper elevations, pointing to the possible importance of grazers, in addition to hydrological processes, as transporters of N throughout this landscape.     

Bradykinin B2 type receptor activation regulates fluid and electrolyte transport in the rabbit kidney

Bradykinin is an important autacoid produced in the kidney, regulating both renal function and blood pressure. In vivo studies in anesthetized rabbits, revealed that BK induced diuresis (UV), natriuresis (U(Na)V) and was not associated with renal hemodynamic changes. These diuretic and natriuretic effects were blocked by the BK-B2 antagonist HOE-140. BK also inhibits vasopressin (AVP)-stimulated water flow (L(p)) in microperfused rabbit cortical collecting ducts (rCCD), in a concentration-dependent fashion, consistent with its in vivo diuretic effects. BK-B1 antagonist Leu8-des-Arg9-BK did not alter the effect of BK on Lp, but HOE-140 completely blocked the inhibitory effects of BK on Lp. While BK did not increase [Ca2+]i in fura-2 loaded freshly microdissected rCCD, BK increased [Ca2+]i in immortalized cultured rCCD cells demonstrating different signaling mechanisms are activated by BK in microdissected versus cultured rCCD. In microperfused rCCD, neither the protein kinase C inhibitor staurosporine nor the phospholipase C (PLC) inhibitor U-73,122 attenuated the BK response arguing against activation of PLC/PKC by BK in rCCD. We conclude: (1) BK induces UV and U(Na)V by a BK-B(2) receptor; (2) BK inhibits AVP-stimulated Lp by a BK-B2 receptor suggesting that its effects on Lp are not via a PLC/PKC; (3) finally, BK raises [Ca2+]i in rCCD cells by a BK-B2 receptor mechanism.     

Ligand-dependent differences in estrogen receptor beta-interacting proteins identified in lung adenocarcinoma cells corresponds to estrogenic responses

Background

A recent epidemiological study demonstrated a reduced risk of lung cancer mortality in breast cancer patients using antiestrogens. These and other data implicate a role for estrogens in lung cancer, particularly nonsmall cell lung cancer (NSCLC). Approximately 61% of human NSCLC tumors express nuclear estrogen receptor β (ERβ); however, the role of ERβ and estrogens in NSCLC is likely to be multifactorial. Here we tested the hypothesis that proteins interacting with ERβ in human lung adenocarcinoma cells that respond proliferatively to estradiol (E₂) are distinct from those in non-E₂-responsive cells.

Methods

FLAG affinity purification of FLAG-ERβ-interacting proteins was used to isolate ERβ-interacting proteins in whole cell extracts from E₂ proliferative H1793 and non-E₂-proliferative A549 lung adenocarcinoma cell lines. Following trypsin digestion, proteins were identified using liquid chromatography electrospray ionization tandem mass spectrometry (LC-MS/MS). Proteomic data were analyzed using Ingenuity Pathway Analysis. Select results were confirmed by coimmunoprecipitation.

Results

LC-MS/MS identified 27 non-redundant ERβ-interacting proteins. ERβ-interacting proteins included hsp70, hsp60, vimentin, histones and calmodulin. Ingenuity Pathway Analysis of the ERβ-interacting proteins revealed differences in molecular and functional networks between H1793 and A549 lung adenocarcinoma cells. Coimmunoprecipitation experiments in these and other lung adenocarcinoma cells confirmed that ERβ and EGFR interact in a gender-dependent manner and in response to E₂ or EGF. BRCA1 interacted with ERβ in A549 cell lines and in human lung adenocarcinoma tumors, but not normal lung tissue.

Conclusion

Our results identify specific differences in ERβ-interacting proteins in lung adenocarcinoma cells corresponding to ligand-dependent differences in estrogenic responses.

     

Root distribution of different mature tree species growing on contrasting textured soils in temperate windbreaks

Aim

We studied the vertical and lateral root distribution of tree species from three genera (Populus spp. - poplar, Picea spp. - spruce, Salix spp. - willow) that were planted in temperate windbreaks and assessed the effects of soil texture on root density.

Methods

Root distribution to depths of up to 1 m was assessed using the trench-profile method at different distances from the tree rows (2, 6 and 9 m) in 18 mature (average age, 25 years-old) windbreak-sites that were located on light- or heavy-textured agricultural soils in southeastern Québec, Canada. Roots were classified into three diameter classes: fine (<1 mm), medium-size (1–5 mm), and coarse (>5 mm).

Results

Tree fine-root density in poplar and willow windbreaks was higher than in spruce windbreaks at 2 m from the tree row. Root densities were higher in light compared to heavy soils, but these differences were specific to poplar and spruce. Across species groups and soil types, 67 % of the roots occurred in the uppermost 30 cm. In this soil zone, different soil fertility variables (pH, clay content, CEC) were negatively correlated with root density. Densities of spruce and willow roots at 6 m from the tree row were much lower (and often unobserved) than that of poplar. At 9 m, low root densities were observed at only two sites.

Conclusions

We conclude that tree identity and soil type are important drivers of root distribution in temperate agroforestry systems. These results may have important implications for the management of tree competition in agroforestry systems and several ecosystem services that are provided by roots, including C-sequestration, erosion control and water infiltration.