Carpeloidy in flower evolution and diversification: a comparative study in Carica papaya and Arabidopsis thaliana

Background and Aims

Bisexual flowers of Carica papaya range from highly regular flowers to morphs with various fusions of stamens to the ovary. Arabidopsis thaliana sup1 mutants have carpels replaced by chimeric carpel–stamen structures. Comparative analysis of stamen to carpel conversions in the two different plant systems was used to understand the stage and origin of carpeloidy when derived from stamen tissues, and consequently to understand how carpeloidy contributes to innovations in flower evolution.

Methods

Floral development of bisexual flowers of Carica was studied by scanning electron microscopy and was compared with teratological sup mutants of A. thaliana.

Key Results

In Carica development of bisexual flowers was similar to wild (unisexual) forms up to locule initiation. Feminization ranges from fusion of stamen tissue to the gynoecium to complete carpeloidy of antepetalous stamens. In A. thaliana, partial stamen feminization occurs exclusively at the flower apex, with normal stamens forming at the periphery. Such transformations take place relatively late in development, indicating strong developmental plasticity of most stamen tissues. These results are compared with evo-devo theories on flower bisexuality, as derived from unisexual ancestors. The Arabidopsis data highlight possible early evolutionary events in the acquisition of bisexuality by a patchy transformation of stamen parts into female parts linked to a flower axis-position effect. The Carica results highlight tissue-fusion mechanisms in angiosperms leading to carpeloidy once bisexual flowers have evolved.

Conclusions

We show two different developmental routes leading to stamen to carpel conversions by late re-specification. The process may be a fundamental aspect of flower development that is hidden in most instances by developmental homeostasis.     

PIN polarity maintenance by the cell wall in Arabidopsis

A central question in developmental biology concerns the mechanism of generation and maintenance of cell polarity, because these processes are essential for many cellular functions and multicellular development. In plants, cell polarity has an additional role in mediating directional transport of the plant hormone auxin that is crucial for multiple developmental processes. In addition, plant cells have a complex extracellular matrix, the cell wall, whose role in regulating cellular processes, including cell polarity, is unexplored. We have found that polar distribution of PIN auxin transporters in plant cells is maintained by connections between polar domains at the plasma membrane and the cell wall. Genetic and pharmacological interference with cellulose, the major component of the cell wall, or mechanical interference with the cell wall disrupts these connections and leads to increased lateral diffusion and loss of polar distribution of PIN transporters for the phytohormone auxin. Our results reveal a plant-specific mechanism for cell polarity maintenance and provide a conceptual framework for modulating cell polarity and plant development via endogenous and environmental manipulations of the cellulose-based extracellular matrix.     

Exact low-force kinetics from high-force single-molecule unfolding events

Mechanical forces play a key role in crucial cellular processes involving force-bearing biomolecules, as well as in novel single-molecule pulling experiments. We present an exact method that enables one to extrapolate, to low (or zero) forces, entire time-correlation functions and kinetic rate constants from the conformational dynamics either simulated numerically or measured experimentally at a single, relatively higher, external force. The method has twofold relevance: 1), to extrapolate the kinetics at physiological force conditions from molecular dynamics trajectories generated at higher forces that accelerate conformational transitions; and 2), to extrapolate unfolding rates from experimental force-extension single-molecule curves. The theoretical formalism, based on stochastic path integral weights of Langevin trajectories, is presented for the constant-force, constant loading rate, and constant-velocity modes of the pulling experiments. For the first relevance, applications are described for simulating the conformational isomerization of alanine dipeptide; and for the second relevance, the single-molecule pulling of RNA is considered. The ability to assign a weight to each trace in the single-molecule data also suggests a means to quantitatively compare unfolding pathways under different conditions.     

Kabuki syndrome: description of a 2-year old Roumanian boy and review of the literature

We report on a 2-year-old boy presenting the cardinal features of the Kabuky syndrome i.e. peculiar face, short stature moderate mental retardation, padded fingers, padded toes and shawl scrotum. Karyotype was 46, XY. Fish tests for microdeletion: 22q11 and 16q (Rubinstein Tayby) were normal.     

Nonionic, Water Self-Dispersible "Hairy-Rod" Poly(p-phenylene)-g-poly(ethylene glycol) Copolymer/Carbon Nanotube Conjugates for Targeted Cell Imaging

The generation and fabrication of nanoscopic structures are of critical technological importance for future implementations in areas such as nanodevices and nanotechnology, biosensing, bioimaging, cancer targeting, and drug delivery. Applications of carbon nanotubes (CNTs) in biological fields have been impeded by the incapability of their visualization using conventional methods. Therefore, fluorescence labeling of CNTs with various probes under physiological conditions has become a significant issue for their utilization in biological processes. Herein, we demonstrate a facile and additional fluorophore-free approach for cancer cell-imaging and diagnosis by combining multiwalled CNTs with a well-known conjugated polymer, namely, poly(p-phenylene) (PP). In this approach, PP decorated with poly(ethylene glycol) (PEG) was noncovalently (π-π stacking) linked to acid-treated CNTs. The obtained water self-dispersible, stable, and biocompatible f-CNT/PP-g-PEG conjugates were then bioconjugated to estrogen-specific antibody (anti-ER) via -COOH functionalities present on the side-walls of CNTs. The resulting conjugates were used as an efficient fluorescent probe for targeted imaging of estrogen receptor overexpressed cancer cells, such as MCF-7. In vitro studies and fluorescence microscopy data show that these conjugates can specifically bind to MCF-7 cells with high efficiency. The represented results imply that CNT-based materials could easily be fabricated by the described approach and used as an efficient "fluorescent probe" for targeting and imaging, thereby providing many new possibilities for various applications in biomedical sensing and diagnosis.     

Hybrid repair of a very late, post-aortic coarctation surgery thoracic aneurysm: a case report

ABSTRACT: INTRODUCTION: Local aneurysms after surgical repair of coarctation of the aorta occur mainly in patients surgically treated by Dacron patch plasty during adulthood. The management of these patients is always problematic, with frequent complications and increased mortality rates. Percutaneous stent-graft implantation avoids the need for surgical reintervention. CASE PRESENTATION: We report a case involving the hybrid treatment by stent-graft implantation and transposition of the left subclavian artery to the left common carotid artery of an aneurysmal dilatation of the thoracic aorta that occurred in a 64-year-old Caucasian man, operated on almost 40 years earlier with a Dacron patch plasty for aortic coarctation. Our patient presented to our facility for evaluation with back pain and shortness of breath after minimal physical effort. A physical examination revealed stony dullness to percussion of the left posterior thorax, with no other abnormalities. The results of chest radiography, followed by contrast-enhanced computed tomography and aortography, led to a diagnosis of giant aortic thoracic aneurysm. Successful treatment of the aneurysm was achieved by percutaneous stent-graft implantation combined with transposition of the left subclavian artery to the left common carotid artery. His post-procedural recovery was uneventful. Three months after the procedure, computed tomography showed complete thrombosis of the excluded aneurysm, without any clinical signs of left lower limb ischemia or new onset neurological abnormalities. CONCLUSIONS: Our patient's case illustrates the clinical outcomes of surgical interventions for aortic coarctation. However, the very late appearance of a local aneurysm is rather unusual. Management of such cases is always difficult. The decision-making should be multidisciplinary. A hybrid approach was considered the best solution for our patient.     

DFT and the electromerism in complexes of iron with diatomic ligands

A reliable procedure is proposed for assigning the electronic structures for large biologically-relevant systems, where the size of the model confines one to the use of density functional theory (DFT) methods, and where the risk of over-interpreting DFT-derived molecular orbitals and spin densities still exists. The proposed approach focuses on the use of the only DFT-derived parameter that is unanimously recognized to be reliable: the geometry. We examine DFT-derived O-O bond lengths in formally ferrous-dioxygen models, and compare them to bond lengths in free, non metal-bound, dioxygen, superoxide and peroxide moieties. Likewise, we compare the N-O bond lengths within ferrous-nitrosyl {FeNO}7 models, with the same parameter in free NO+, NO*, and HNO species. This allows a calibrated, straightforward way of assigning the electronic structure in systems where electromerism makes detailed single-reference molecular orbital analysis unreliable.     

Mechanistic mathematical model for in vivo aroma release during eating of semiliquid foods

The paper describes a mechanistic mathematical model for aroma release in the oropharynx to the nasal cavity during food consumption. The model is based on the physiology of the swallowing process and is validated with atmospheric pressure chemical ionization coupled with mass spectrometry measurements of aroma concentration in the nasal cavity of subjects eating flavored yogurt. The study is conducted on 3 aroma compounds representative for strawberry flavor (ethyl acetate, ethyl butanoate, and ethyl hexanoate) and 3 panelists. The model provides reasonably accurate time predictions of the relative aroma concentration in the nasal cavity and is able to simulate successive swallowing events as well as imperfect velopharyngeal closure. The most influent parameters are found to be the amount of the residual product in the pharynx and its contact area with the air flux, the volume of the nasal cavity, the equilibrium air/product partition coefficient of the volatile compound, the breath airflow rate, as well as the mass transfer coefficient of the aroma compound in the product, and the amount of product in the mouth. This work constitutes a first step toward computer-aided product formulation by allowing calculation of retronasal aroma intensity as a function of transfer and volatility properties of aroma compounds in food matrices and anatomophysiological characteristics of consumers.