Plant hydraulics as a central hub integrating plant and ecosystem function: meeting report for ‘Emerging Frontiers in Plant Hydraulics’ (Washington,DC, May 2015)

Water plays a central role in plant biology and the efficiency of water transport throughout the plant affects both photosynthetic rate and growth, an influence that scales up deterministically to the productivity of terrestrial ecosystems. Moreover, hydraulic traits mediate the ways in which plants interact with their abiotic and biotic environment. At landscape to global scale, plant hydraulic traits are important in describing the function of ecological communities and ecosystems. Plant hydraulics is increasingly recognized as a central hub within a network by which plant biology is connected to palaeobiology, agronomy, climatology, forestry, community and ecosystem ecology and earth‐system science. Such grand challenges as anticipating and mitigating the impacts of climate change, and improving the security and sustainability of our food supply rely on our fundamental knowledge of how water behaves in the cells, tissues, organs, bodies and diverse communities of plants. A workshop, ‘Emerging Frontiers in Plant Hydraulics’ supported by the National Science Foundation, was held in Washington DC, 2015 to promote open discussion of new ideas, controversies regarding measurements and analyses, and especially, the potential for expansion of up‐scaled and down‐scaled inter‐disciplinary research, and the strengthening of connections between plant hydraulic research, allied fields and global modelling efforts.     

Antagonistic Effect of a Salivary Proline-Rich Peptide on the Cytosolic Ca2+ Mobilization Induced by Progesterone in Oral Squamous Cancer Cells

A salivary proline-rich peptide of 1932 Da showed a dose-dependent antagonistic effect on the cytosolic Ca²⁺ mobilization induced by progesterone in a tongue squamous carcinoma cell line. Structure-activity studies showed that the activity of the peptide resides in the C-terminal region characterized by a proline stretch flanked by basic residues. Furthermore, lack of activity of the retro-inverso peptide analogue suggested the involvement of stereospecific recognition. Mass spectrometry-based shotgun analysis, combined with Western blotting tests and biochemical data obtained with the Progesterone Receptor Membrane Component 1 (PGRMC1) inhibitor AG205, showed strong evidence that p1932 performs its modulatory action through an interaction with the progesterone receptor PGRMC1, which is predominantly expressed in this cell line and, clearly, plays a role in progesterone induced Ca²⁺ response. Thus, our results point to p1932 as a modulator of the transduction signal pathway mediated by this protein and, given a well-established involvement of PGRMC1 in tumorigenesis, highlight a possible therapeutic potential of p1932 for the treatment of oral cancer.     

Evidence for a Selective Localization of Voltage-Sensitive Ca2+ Channels in Nerve Cell Bodies of Corpus Striatum

Specific binding sites for [3H]nitrendipine, an organic Ca2+ channel antagonist, were abolished in crude synaptosomal membranes of kainic acid-lesioned caudate nuclei. In contrast, specific lesions of dopaminergic or serotonergic axon terminals in caudate nuclei failed to alter the density or the affinity of [3H]nitrendipine binding sites. In addition, the basal and veratridine-stimulated 45Ca2+ accumulations were greatly impaired in slices prepared from kainic acid-lesioned caudate nuclei. The veratridine-elicited accumulation of 45Ca2+ in control slices was attenuated by addition of tetrodotoxin in the incubation medium. The present data provide evidence that most of the [3H]nitrendipine binding sites and the voltage-dependent Ca2+ channels are located in intrinsic neurons or interneurons in caudate nucleus. In contrast, destruction of dopaminergic or serotonergic nerve terminals emanating from other brain areas and innervating the caudate nucleus failed to change the apparent Bmax value for [3H]nitrendipine binding.     

Foot-shock stress enhances the increase of [35S]TBPS binding in the rat cerebral cortex and the convulsions induced by isoniazid

We report earlier that isoniazid and foot-shock stress individually increase the maximal number of [³⁵S]TBPS binding sites (B_max) measured ex vivo in unwashed membranes from rat cerebral cortex and that the increase due to both treatments are prevented by pretreatment in vivo with diazepam which alone induced a significant decrease in the total number of [³⁵S]TBPS binding sites. In the present paper, the effect of stress was studied on both the increase in [³⁵S]TBPS binding and the convulsant activity induced by isoniazid in unstressed rats. Isoniazid induced a time dependent increase in [³⁵S]TBPS binding. The isoniazid-induced increase in [³⁵S]TBPS binding was markedly potentiated by foot-shock stress. Moreover, foot-shock stress markedly reduced the latency to the appearance of generalized seizures induced by isoniazid (300 mg/kg s.c.). The results provide evidence that the in vivo inhibition of GABAergic transmission elicited by isoniazid results in an increase of [³⁵S]TBPS binding in the rats cerebral cortex. The finding that stress, like isoniazid, enhances [³⁵S]TBPS binding suggests that this treatment also inhibits the function of GABAergic synapses.     

Inhibition of GGTase‐I and FTase disrupts cytoskeletal organization of human PC‐3 prostate cancer cells

The mevalonate synthesis pathway produces intermediates for isoprenylation of small GTPases, which are involved in the regulation of actin cytoskeleton and cell motility. Here, we investigated the role of the prenylation transferases in the regulation of the cytoskeletal organization and motility of PC‐3 prostate cancer cells. This was done by using FTI‐277, GGTI‐298 or NE‐10790, the specific inhibitors of FTase (farnesyltransferase), GGTase (geranylgeranyltransferase)‐I and ‐II, respectively. Treatment of PC‐3 cells with GGTI‐298 and FTI‐277 inhibited migration and invasion in a time‐ and dose‐dependent manner. This was associated with disruption of F‐actin organization and decreased recovery of GFP–actin. Immunoblot analysis of various cytoskeleton‐associated proteins showed that the most striking change in GGTI‐298‐ and FTI‐277‐treated cells was a markedly decreased level of total and phosphorylated cofilin, whereas the level of cofilin mRNA was not decreased. The treatment of PC‐3 cells with GGTI‐298 also affected the dynamics of GFP–paxillin and decreased the levels of total and phosphorylated paxillin. The levels of phosphorylated FAK (focal adhesion kinase) and PAK (p‐21‐associated kinase)‐2 were also lowered by GGTI‐298, but levels of paxillin or FAK mRNAs were not affected. In addition, GGTI‐298 had a minor effect on the activity of MMP‐9. RNAi knockdown of GGTase‐Iβ inhibited invasion, disrupted F‐actin organization and decreased the level of cofilin in PC‐3 cells. NE‐10790 did not have any effect on PC‐3 prostate cancer cell motility or on the organization of the cytoskeleton. In conclusion, our results demonstrate the involvement of GGTase‐I‐ and FTase‐catalysed prenylation reactions in the regulation of cytoskeletal integrity and motility of prostate cancer cells and suggest them as interesting drug targets for development of inhibitors of prostate cancer metastasis.     

Distinct Muscle Biopsy Findings in Genetically Defined Adult-Onset Motor Neuron Disorders

The objective of this study was to characterize and compare muscle histopathological findings in 3 different genetic motor neuron disorders. We retrospectively re-assessed muscle biopsy findings in 23 patients with autosomal dominant lower motor neuron disease caused by p.G66V mutation in CHCHD10 (SMAJ), 10 X-linked spinal and bulbar muscular atrophy (SBMA) and 11 autosomal dominant c9orf72-mutated amyotrophic lateral sclerosis (c9ALS) patients. Distinct large fiber type grouping consisting of non-atrophic type IIA muscle fibers were 100% specific for the late-onset spinal muscular atrophies (SMAJ and SBMA) and were never observed in c9ALS. Common, but less specific findings included small groups of highly atrophic rounded type IIA fibers in SMAJ/SBMA, whereas in c9ALS, small group atrophies consisting of small-caliber angular fibers involving both fiber types were more characteristic. We also show that in the 2 slowly progressive motor neuron disorders (SMAJ and SBMA) the initial neurogenic features are often confused with considerable secondary “myopathic” changes at later disease stages, such as rimmed vacuoles, myofibrillar aggregates and numerous fibers reactive for fetal myosin heavy chain (dMyHC) antibodies. Based on our findings, muscle biopsy may be valuable in the diagnostic work-up of suspected motor neuron disorders in order to avoid a false ALS diagnosis in patients without clear findings of upper motor neuron lesions.     

Influence of genetic drift on patterns of genetic variation: The footprint of aquaculture practices in Sparus aurata (Teleostei: Sparidae)

Aquaculture finfish production based on floating cage technology has raised increasing concerns regarding the genetic integrity of natural populations. Accidental mass escapes can induce the loss of genetic diversity in wild populations by increasing genetic drift and inbreeding. Farm escapes probably represent an important issue in the gilthead sea bream (Sparus aurata), which accounted for 76.4% of total escapees recorded in Europe during a 3‐year survey. Here, we investigated patterns of genetic variation in farmed and wild populations of gilthead sea bream from the Western Mediterranean, a region of long gilthead sea bream farming. We focused on the role that genetic drift may play in shaping these patterns. Results based on microsatellite markers matched those observed in previous studies. Farmed populations showed lower levels of genetic diversity than wild populations and were genetically divergent from their wild counterparts. Overall, farmed populations showed the smallest effective population size and increased levels of relatedness compared to wild populations. The small broodstock size coupled with breeding practices that may favour the variance in individual reproductive success probably boosted genetic drift. This factor appeared to be a major driver of the genetic patterns observed in the gilthead sea bream populations analysed in the present study. These results further stress the importance of recommendations aimed at maintaining broodstock sizes as large as possible and equal sex‐ratios among breeders, as well as avoiding unequal contributions among parents.     

Impaired gap junction formation and intercellular calcium signaling in urinary bladder cancer cells can be improved by Gö6976

PURPOSE: Calcium wave propagation and connexin 26, 32 and 43 expression were studied in normal and malignant urothelial cells. MATERIALS AND METHODS: Human urothelial cell cultures were established from tissue biopsies obtained from three healthy control persons and compared to human transitional cell carcinoma (TCC) cell line 5637. Fluo-3 was used to study intercellular calcium signaling in urothelial cells. The cells were stimulated mechanically in the presence of inhibitors of gap-junctional or ATP-mediated communication to determine which pathways are operative in intercellular calcium signaling. In addition, G?6976 was used to determine the effects of PKC alpha and betaI inhibition on intercellular calcium signaling. RESULTS: In normal urothelial cells, the primary pathway for intercellular calcium mediated cell signaling was gap junctional intercellular communication (GJIC), but the paracrine ATP-mediated signaling was also operative. In 5637 TCC cells, GJIC and ATP-mediated signaling routes were altered when compared to normal urothelial cells. More specifically, inhibition of GJIC resulted in a complete block of intercellular calcium signaling, while inhibition of ATP-mediated signaling decreased signal transduction in 5637 TCC cells. The results of the present study also demonstrated that connexin 26 was the most abundant gap junction plaque protein in cultured normal human urothelial cells and that it did not form gap junction plaques in 5637 TCC cell culture. Treatment with G?6976 induced gap junction plaque formation by connexin 26 in 5637 TCC cells. In addition, the exposure to G?6976 enhanced intercellular calcium mediated signaling in 5637 TCC cells, but not in normal cells. CONCLUSIONS: The results of the present study suggest that gap junctions play a major role in intercellular calcium signaling in urothelial cells. In addition, intercellular calcium signaling is altered in urinary bladder carcinoma cells, and it can be improved by PKC alpha and betaI inhibition. (Supplementary materials are available for this article. Go to the publisher's online edition of Cell Communication and Adhesion for the following free supplemental resources; Movie files of Fig. 2normal G?6976-, normal G?6976+, TCC G?6976-, TCC G?6976+ and image of Supplementary Figure 1).     

The GLUT9 gene is associated with serum uric acid levels in Sardinia and Chianti cohorts

High serum uric acid levels elevate pro-inflammatory–state gout crystal arthropathy and place individuals at high risk for cardiovascular morbidity and mortality. Genome-wide scans in the genetically isolated Sardinian population identified variants associated with serum uric acid levels as a quantitative trait. They mapped within GLUT9, a Chromosome 4 glucose transporter gene predominantly expressed in liver and kidney. SNP rs6855911 showed the strongest association (p = 1.84 × 10⁻¹⁶), along with eight others (p = 7.75 × 10⁻¹⁶ to 6.05 × 10⁻¹¹). Individuals homozygous for the rare allele of rs6855911 (minor allele frequency = 0.26) had 0.6 mg/dl less uric acid than those homozygous for the common allele; the results were replicated in an unrelated cohort from Tuscany. Our results suggest that polymorphisms in GLUT9 could affect glucose metabolism and uric acid synthesis and/or renal reabsorption, influencing serum uric acid levels over a wide range of values.