Interaction of nitrogen and phosphorus nutrition in determining growth

In this paper we discuss the differences and similarities in the growth response of tomato plants to N and P limitation, and to their interaction. Two detailed growth experiments, with varied N or P supply, were conducted in order to unravel the effects of N and P limitation on growth of young tomato plants (Lycopersicon esculentum Mill.). Relative growth rate (RGR) initially increased sharply with increasing plant P concentration but leveled off at higher plant P concentrations. In contrast, RGR increased gradually with increasing plant N concentration before it leveled off at higher plant N concentrations. The relationship of RGR with organic leaf N and P showed the same shape as with total N and P concentrations, respectively. The difference in response is most likely due to the different roles of N and P in the machinery of the plant's energy metabolism (e.g., photosynthesis, respiration). Plant N concentration decreased with increasing P limitation. We show that this decrease cannot be explained by a shift in dry-mass partitioning. Our results suggest that the decrease in N concentration with increasing P limitation may be mediated by a decrease in leaf cytokinin levels and is less likely due to decreased energy availability at low P conditions. Dry-mass partitioning to the roots was closely linearly related to the leaf reduced-N concentration. However, treatments that were severely P limited deviated from this relationship.     

Aqua bridge cleavage and metal ion extrusion by thiocyanate anions in a dicopper complex

Reaction of the imidazolidinyl phenolate-based ligand, H₃L [(2-(2′-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine)] with Cu(ClO₄)₂·6H₂O produces an aqua-bridged cationic reactant complex [Cu₂(μ-H₂O)(μ-L)][ClO₄]·1.5H₂O (1·1.5H₂O). Solution phase interaction of 1·1.5H₂O with SCN⁻ anions in 1:1 molar ratio leads to [Cu₂(μ-L)(NCS)]·2H₂O (2·2H₂O) that does not possess anymore the reactive aqua bridge but instead a terminal SCN⁻ anion coordinated only to one Cu^II ion. Whereas in 1:2 molar ratio, partial extrusion of the Cu^II ions takes place to generate in situ [Cu(NCS)₃(OH₂)]⁻ anions. These complex anions then quantitatively replace anions in 1·1.5H₂O via ‘anion metathesis’ and concurrently remove the aqua bridge by coordination of linear MeCN to one of the Cu^II ions to give [Cu₂(μ-L)(CH₃CN)][Cu(NCS)₃(OH₂)] (3). The literature unknown [Cu(NCS)₃(OH₂)]⁻ anion forms an intimate H-bonded assembly with the cationic part of 3 to yield a novel [Cu₃] isosceles triangle. The precursor complex is known as antiferromagnetic whereas in 2·2H₂O, the Cu^II (S = 1/2) ions in a dinuclear entity exhibit ferromagnetic interactions (J/k_B = +15.0 K and g = 2.22) to yield an S_T = 1 spin ground state in good agreement with the M versus H data below 8 K.     

Ovarian Cancer Cell Line Panel (OCCP): Clinical Importance of In Vitro Morphological Subtypes

Epithelial ovarian cancer is a highly heterogeneous disease and remains the most lethal gynaecological malignancy in the Western world. Therapeutic approaches need to account for inter-patient and intra-tumoural heterogeneity and detailed characterization of in vitro models representing the different histological and molecular ovarian cancer subtypes is critical to enable reliable preclinical testing. There are approximately 100 publicly available ovarian cancer cell lines but their cellular and molecular characteristics are largely undescribed. We have characterized 39 ovarian cancer cell lines under uniform conditions for growth characteristics, mRNA/microRNA expression, exon sequencing, drug response for clinically-relevant therapeutics and collated all available information on the original clinical features and site of origin. We tested for statistical associations between the cellular and molecular features of the lines and clinical features. Of the 39 ovarian cancer cell lines, 14 were assigned as high-grade serous, four serous-type, one low-grade serous and 20 non-serous type. Three morphological subtypes: Epithelial (n = 21), Round (n = 7) and Spindle (n = 12) were identified that showed distinct biological and molecular characteristics, including overexpression of cell movement and migration-associated genes in the Spindle subtype. Comparison with the original clinical data showed association of the spindle-like tumours with metastasis, advanced stage, suboptimal debulking and poor prognosis. In addition, the expression profiles of Spindle, Round and Epithelial morphologies clustered with the previously described C1-stromal, C5-mesenchymal and C4 ovarian subtype expression profiles respectively. Comprehensive profiling of 39 ovarian cancer cell lines under controlled, uniform conditions demonstrates clinically relevant cellular and genomic characteristics. This data provides a rational basis for selecting models to develop specific treatment approaches for histological and molecular subtypes of ovarian cancer.     

Synthesis of Tricyclic Phenylpyrrole Lactams, New Models of Antitubulin Agents

The tricyclic lactams 3 and 4 having a phenylpyrrole framework have been prepared from the arylpyrroles 5 and 16 respectively. These structural analogs of rhazinilam 1 present, like the latter, an interesting antitubulin and cytotoxic activity.     

Contrasting effects of N and P deprivation on the regulation of photosynthesis in tomato plants in relation to feedback limitation

The effects were studied of both nitrogen and phosphorus limitation and irradiance on the performance and operation of photosynthesis in tomato leaves (Lycopersicon esculentum Mill.). Plants were grown at low N, high N, low P or high P supply and at two irradiances. Using mature leaves, measurements were made of the irradiance dependencies of the relative quantum efficiencies of photosystems I and II, and of the rate of carbon dioxide fixation. Measurements were also made of foliar starch and chlorophyll concentrations. The results showed that photosynthetic light-harvesting and electron-transport activity acclimate to nutrient stress and growth irradiance such that the internal relationships between electron transport by photosystems I and II do not change; the linear relationship between PhiPSII, and PhiPSI was not affected. It was also evident that under N stress photosynthesis was reduced by a decreased light absorption and by the decreased utilization of assimilates, while P stress mainly affected the carboxylation capacity. Under N stress foliar starch levels increased and the oxygen sensitivity of CO2 fixation decreased, whereas P stress resulted in decreased starch levels and increased oxygen sensitivity of CO2 fixation. The relationship between starch accumulation and oxygen sensitivity (increased starch correlated with decreased oxygen sensitivity) was always the same across the nutrient treatments. These results are consistent with N deprivation producing an increasing limitation of photosynthesis, possibly by feedback from the leaf carbohydrate pool, whereas, although P deprivation produces a decreased rate of CO2 fixation, this is accompanied by a increase in oxygen sensitivity, suggesting that feedback limitation is decreased under P stress.