Asymptotic optimal SINR performance bound for space-time beamforming

International audienceIn many detection applications, the main performance criterion is the signal to interference plus noise ratio (SINR). After linear filtering, the optimal SINR corresponds to the maximum value of a Rayleigh quotient, which can be interpreted as the largest generalized eigenvalue of two covariance matrices. Using an extension of Szegö's theorem for the generalized eigenvalues of Hermitian block Toeplitz matrices, an expression of the theoretical asymptotic optimal SINR w.r.t. the number of taps is derived for arbitrary arrays with a limited but arbitrary number of sensors and arbitrary spectra. This bound is interpreted as an optimal zero-bandwidth spatial SINR in some sense. Finally, the speed of convergence of the optimal wideband SINR for a limited number of taps is analyzed for several interference scenario

Antibrouillage radar en contexte de rotation d'antenne

- Nous nous intéressons dans cet article à l'algorithme Opposition dans les Lobes Secondaires (OLS) utilisé en traitement d'antenne RADAR dans un but d'antibrouillage en contexte de rotation d'antenne. Nous montrons que l'utilisation de la méthode Extended Sample Matrix Inversion (ESMI) [2] conduit alors à des performances supérieures à la méthode standard

Field-Based Metabolomics of Vitis vinifera L. Stems Provides New Insights for Genotype Discrimination and Polyphenol Metabolism Structuring

Grape accumulates numerous polyphenols with abundant health benefit and organoleptic properties that in planta act as key components of the plant defense system against diseases. Considerable advances have been made in the chemical characterization of wine metabolites particularly volatile and polyphenolic compounds. However, the metabotyping (metabolite-phenotype characterization) of grape varieties, from polyphenolic-rich vineyard by-product is unprecedented. As this composition might result from the complex interaction between genotype, environment and viticultural practices, a field experiment was setting up with uniform pedo-climatic factors and viticultural practices of growing vines to favor the genetic determinism of polyphenol expression. As a result, UPLC-MS-based targeted metabolomic analyses of grape stems from 8 Vitis vinifera L. cultivars allowed the determination of 42 polyphenols related to phenolic acids, flavonoids, procyanidins, and stilbenoids as resveratrol oligomers (degree of oligomerization 1–4). Using a partial least-square discriminant analysis approach, grape stem chemical profiles were discriminated according to their genotypic origin showing that polyphenol profile express a varietal signature. Furthermore, hierarchical clustering highlights various degree of polyphenol similarity between grape varieties that were in agreement with the genetic distance using clustering analyses of 22 microsatellite DNA markers. Metabolite correlation network suggested that several polyphenol subclasses were differently controlled. The present polyphenol metabotyping approach coupled to multivariate statistical analyses might assist grape selection programs to improve metabolites with both health-benefit potential and plant defense traits

A single gene encodes isopentenyl diphosphate isomerase isoforms targeted to plastids, mitochondria and peroxisomes in Catharanthus roseus

Isopentenyl diphosphate isomerases (IDI) catalyze the interconversion of the two isoprenoid universal C5 units, isopentenyl diphosphate and dimethylally diphosphate, to allow the biosynthesis of the large variety of isoprenoids including both primary and specialized metabolites. This isomerisation is usually performed by two distinct IDI isoforms located either in plastids/peroxisomes or mitochondria/peroxisomes as recently established in Arabidopsis thaliana mainly accumulating primary isoprenoids. By contrast, almost nothing is known in plants accumulating specialized isoprenoids. Here we report the cloning and functional validation of an IDI encoding cDNA (CrIDI1) from Catharanthus roseus that produces high amount of monoterpenoid indole alkaloids. The corresponding gene is expressed in all organs including roots, flowers and young leaves where transcripts have been detected in internal phloem parenchyma and epidermis. The CrIDI1 gene also produces long and short transcripts giving rise to corresponding proteins with and without a N-terminal transit peptide (TP), respectively. Expression of green fluorescent protein fusions revealed that the long isoform is targeted to both plastids and mitochondria with an apparent similar efficiency. Deletion/fusion experiments established that the first 18-residues of the N-terminal TP are solely responsible of the mitochondria targeting while the entire 77-residue long TP is needed for an additional plastid localization. The short isoform is targeted to peroxisomes in agreement with the presence of peroxisome targeting sequence at its C-terminal end. This complex plastid/mitochondria/peroxisomes triple targeting occurring in C. roseus producing specialized isoprenoid secondary metabolites is somehow different from the situation observed in A. thaliana mainly producing housekeeping isoprenoid metabolites.This work was financially supported by the “Ministère de l’Enseignement Supérieur et de la Recherche” (MESR) and by a grant from the University of Tours. Grégory Guirimand and Anthony Guihur were financed by MESR fellowships.Peer reviewe

Triple subcellular targeting of isopentenyl diphosphate isomerases encoded by a single gene

Isopentenyl diphosphate isomerase (IDI) is a key enzyme of the isoprenoid pathway, catalyzing the interconversion of isopentenyl diphosphate and dimethylallyl diphosphate, the universal precursors of all isoprenoids. In plants, several subcellular compartments, including cytosol/ER, peroxisomes, mitochondria and plastids, are involved in isoprenoid biosynthesis. Here, we report on the unique triple targeting of two Catharanthus roseus IDI isoforms encoded by a single gene (CrIDI1). The triple localization of CrIDI1 in mitochondria, plastids and peroxisomes is explained by alternative transcription initiation of CrIDI1, by the specificity of a bifunctional N-terminal mitochondria/plastid transit peptide and by the presence of a C-terminal peroxisomal targeting signal. Moreover, bimolecular fluorescence complementation assays revealed self-interactions suggesting that the IDI likely acts as a multimer in vivo.Peer reviewe

Asymptotic generalized eigenvalue distribution of Toeplitz block Toeplitz matrices

International audienceIn many detection and estimation problems associated with processing of second order stationary 2-D discrete random processes, the observation data are the sum of two zero-mean second order stationary processes: the process of interest and the noise process. In particular, the main performance criterion is the Signal to Noise Ratio (SNR). After linear filtering, the optimal SNR corresponds to the maximal value of a Rayleigh quotient which can be interpreted as the largest generalized eigenvalue of the covariance matrices associated with the signal and noise processes, which are Toeplitz block Toeplitz structured. In this paper, an extension of Szego's theorem to the generalized eigenvalues of Hermitian Toeplitz block Toeplitz matrices is given, under the hypothesis of absolutely summable elements, providing information about the asymptotic distribution of those generalized eigenvalues and in particular of the optimal SNR after linear filtering

Synthetic Biology in the Candida (CTG) Clade

International audiencePlant specialized metabolites are widely used in the pharmaceutical industry, including the monoterpene indole alkaloids (MIAs) vinblastine and vincristine, which both display anticancer activity. Both compounds can be obtained through the chemical condensation of their precursors vindoline and catharanthine extracted from leaves of the Madagascar periwinkle. However, the extensive use of these molecules in chemotherapy increases precursor demand and results in recurrent shortages, explaining why the development of alternative production approaches, such microbial cell factories, is mandatory. In this context, the precursor-directed biosynthesis of vindoline from tabersonine in yeast-expressing heterologous biosynthetic genes is of particular interest but has not reached high production scales to date. To circumvent production bottlenecks, the metabolic flux was channeled towards the MIA of interest by modulating the copy number of the first two genes of the vindoline biosynthetic pathway, namely tabersonine 16-hydroxylase and tabersonine-16-O-methyltransferase. Increasing gene copies resulted in an optimized methoxylation of tabersonine and overcame the competition for tabersonine access with the third enzyme of the pathway, tabersonine 3-oxygenase, which exhibits a high substrate promiscuity. Through this approach, we successfully created a yeast strain that produces the fourth biosynthetic intermediate of vindoline without accumulation of other intermediates or undesired side-products. This optimization will probably pave the way towards the future development of yeast cell factories to produce vindoline at an industrial scale