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Showing papers by "Braunschweig University of Technology published in 1998"


Journal ArticleDOI
05 Mar 1998-Nature
TL;DR: A new hypothesis for the origin of eukaryotic cells is proposed, based on the comparative biochemistry of energy metabolism, to have arisen through symbiotic association of an anaerobic, strictly hydrogen-dependent, strictly autotrophic archaebacterium with a eubacterium.
Abstract: A new hypothesis for the origin of eukaryotic cells is proposed, based on the comparative biochemistry of energy metabolism. Eukaryotes are suggested to have arisen through symbiotic association of an anaerobic, strictly hydrogen-dependent, strictly autotrophic archaebacterium (the host) with a eubacterium (the symbiont) that was able to respire, but generated molecular hydrogen as a waste product of anaerobic heterotrophic metabolism. The host's dependence upon molecular hydrogen produced by the symbiont is put forward as the selective principle that forged the common ancestor of eukaryotic cells.

1,154 citations


Journal ArticleDOI
14 May 1998-Nature
TL;DR: The process of gene loss from chloroplast genomes across the inferred tree is mapped and it is found that independent parallel gene losses in multiple lineages outnumber phylogenetically unique losses by more than 4:1.
Abstract: Photosynthetic eukaryotes, particularly unicellular forms, possess a fossil record that is either wrought with gaps or difficult to interpret, or both. Attempts to reconstruct their evolution have focused on plastid phylogeny, but were limited by the amount and type of phylogenetic information contained within single genes. Among the 210 different protein-coding genes contained in the completely sequenced chloroplast genomes from a glaucocystophyte, a rhodophyte, a diatom, a euglenophyte and five land plants, we have now identified the set of 45 common to each and to a cyanobacterial outgroup genome. Phylogenetic inference with an alignment of 11,039 amino-acid positions per genome indicates that this information is sufficient--but just rarely so--to identify the rooted nine-taxon topology. We mapped the process of gene loss from chloroplast genomes across the inferred tree and found that, surprisingly, independent parallel gene losses in multiple lineages outnumber phylogenetically unique losses by more that 4:1. We identified homologues of 44 different plastid-encoded proteins as functional nuclear genes of chloroplast origin, providing evidence for endosymbiotic gene transfer to the nucleus in plants.

754 citations


Journal ArticleDOI
TL;DR: From the functional standpoint, both organelles have retained much more of their eubacterial biochemistry than is reflected in their DNA.
Abstract: Chloroplasts were once free-living cyanobacteria, mitochondria were once free-living proteobacteria, and both have preserved remnants of eubacterial genomes. But from the functional standpoint, both organelles have retained much more of their eubacterial biochemistry than is reflected in their DNA.

695 citations


Journal ArticleDOI
TL;DR: In this paper, the authors constructed the unique optimal quantum device for turning a finite number of d-level quantum systems in the same unknown pure state σ into M systems of the same kind, in an approximation of the M-fold tensor product of σ.
Abstract: We construct the unique optimal quantum device for turning a finite number of d-level quantum systems in the same unknown pure state \sigma into M systems of the same kind, in an approximation of the M-fold tensor product of the state \sigma.

468 citations


Journal ArticleDOI
TL;DR: Biosurfactants may find applications in the near future in the environmental remediation industries, where the requirement for purified molecules is of less importance and the cost of production is considerably higher than for synthetic surfactants.
Abstract: Like other hydrocarbon-oxidising bacteria, rhodococci respond to the presence of alkanes by producing biosurfactant molecules to improve their ability to utilise these hydrophobic compounds as growth substrates. In the rhodococci these surfactants are predominantly glycolipids, the majority of which remain cell-bound during unrestricted growth. Most work has been done on the trehalose mycolates formed by Rhodococcus erythropolis, but nitrogen- limited conditions lead to the production of anionic trehalose tetraesters also.

228 citations


Journal ArticleDOI
TL;DR: The results suggest that BMP-2 is part of the complex of cardiogenic signals and is involved in the patterning of early mesoderm similar to the role of dpp in Drosophila.

209 citations


Journal ArticleDOI
TL;DR: It is argued that new methodologies and AD tools support an integrated hardware software codesign process that begins before the system architecture is finalised.
Abstract: Ever increasing embedded system design complexity combined with a very tight time-to-market window has revolutionized the embedded-system design process. The concurrent design of hardware and software has displaced traditional sequential design. Further, hardware and software design now begins before the system architecture (or even the specification) is finalised. System architects, customers, and marketing departments develop requirement definitions and system specifications together. System architects define a system architecture consisting of cooperating system functions that form the basis of concurrent hardware and software design. Interface design requires the participation of both hardware and software developers. The next step integrates and tests hardware and software-this phase consists of many individual steps. Reusing components taken from previous designs or acquired from outside the design group is a main design goal to improve productivity and reduce design risk. It is argued that new methodologies and AD tools support an integrated hardware software codesign process.

200 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that if the quality judgement is based solely on measurements of single output clones, there is again a unique optimal cloning device, which coincides with the one found previously.
Abstract: We consider quantum devices for turning a finite number N of d-level quantum systems in the same unknown pure state \sigma into M>N systems of the same kind, in an approximation of the M-fold tensor product of the state \sigma. In a previous paper it was shown that this problem has a unique optimal solution, when the quality of the output is judged by arbitrary measurements, involving also the correlations between the clones. We show in this paper, that if the quality judgement is based solely on measurements of single output clones, there is again a unique optimal cloning device, which coincides with the one found previously.

186 citations


Journal ArticleDOI
TL;DR: In this article, four different methods of mechanical cell disintegration were used to investigate the influence of the degree of disintegration and the digestion parameters on the performance of the anaerobic process.

172 citations


Proceedings ArticleDOI
16 May 1998
TL;DR: A novel control scheme that guarantees a lower bound of the end-effector stiffness (LBSC) is presented and is compared with a traditional control scheme for high-speed applications using the minimal 2-norm of actuator torques.
Abstract: A 2-DOF parallel manipulator with actuation redundancy is examined for high-speed and stiffness-controlled operation. Advantages of actuation redundancy are outlined. The kinematics and singularity-free workspace of the manipulator are presented together with a force transmission analysis. Finally, a novel control scheme that guarantees a lower bound of the end-effector stiffness (LBSC) is presented. Simulation results are compared with a traditional control scheme for high-speed applications using the minimal 2-norm of actuator torques.

172 citations


Journal ArticleDOI
TL;DR: It is proposed that PIP2-dependent signalling modulates microfilament organization at cellular adhesion sites by regulating vinculin-VASP complexes.

Proceedings ArticleDOI
01 Jul 1998
TL;DR: This paper extends the well known structures of the control flow graph and the program dependencc graph for threaded programs with interference and calculates more precise static slices which does not require serialization of threaded programs.
Abstract: Static program slicing is an established method for analyzing sequential programs, especially for program understanding, debugging and testing. Until now, there was no slicing method for threaded programs which handles interference correctly. We present such a method which also calculates more precise static slices. This paper extends the well known structures of the control flow graph and the program dependencc graph for threaded programs with interference. This new technique does not require serialization of threaded programs.

Proceedings ArticleDOI
18 May 1998
TL;DR: A method is proposed which considerably reduces the peak-to-average power ratio of the OFDM signal by means of signal processing.
Abstract: An important difficulty which has to be solved in OFDM transmission systems is the large peak-to-average power ratio of the OFDM signal. Without any measures, the signal is limited by the power amplifier in the transmitter which causes interference both of the signal itself and in adjacent frequency bands. A method is proposed which considerably reduces the peak-to-average power ratio of the OFDM signal by means of signal processing.

Journal ArticleDOI
24 Aug 1998-Planta
TL;DR: It is suggested that in constitutive plant defence, without significant turnover of its components, such a highly plastic system provides a powerful strategy to successfully defend and possibly escape herbivory.
Abstract: Laboratory and field tracer experiments with 14C-labelled senecionine N–oxide (SO) and distant biosynthetic precursors such as [14C]putrescine revealed that pyrrolizidine alkaloid N-oxides (PAs) in Senecio vernalis Waldstr. & Kit. (Asteraceae) show no significant turnover over periods of up to 29 d. However, PAs are spatially mobile, they are continuously allocated, and labelled PAs are even detectable in leaves and capitula developed weeks after tracer application. Chemical diversification of SO, the common product of PA biosynthesis in roots, was studied in five Senecio species (i.e. S. vernalis Waldstr. & Kit., S. vulgaris L, S. inaequidens DC, two chemotypes of S. jacobaea L. and S. erucifolius L.). Tracer experiments revealed that shoots are capable of transforming [14 C]SO into the unique species–specific PA patterns. Within a plant, the transformation efficiency of SO can vary quantitatively and qualitatively between shoot organs (i.e. leaves, stems and inflorescences). All transformations proceed position-specifically and stereoselectively. They comprise simple one-step or two-step reactions such as hydroxylations, epoxidations, dehydrogenations, and O-acetylations, as well as the more complex conversion of the retronecine into the otonecine base moiety (e.g. SO into senkirkine). Taking all the evidence together, the qualitative and quantitative composition of the Senecio PA pattern is a dynamic and sensitive equilibrium between a number of interacting processes: (i) constant rate of de-novo synthesis of SO in roots, (ii) continuous long-distance translocation of SO into shoots, (iii) efficiency of SO transformations which may vary between plant organs, (iv) continuous allocation of PAs in the plant, and (v) efficiency and tissue selectivity of vacuolar storage. We suggest that in constitutive plant defence, without significant turnover of its components, such a highly plastic system provides a powerful strategy to successfully defend and possibly escape herbivory.

Journal ArticleDOI
TL;DR: The data show that the age or gonadotropin‐dependent expression of PHGPx in testis does not result from direct transcriptional gene activation by testosterone, but is due to differentiation stage‐specific expression in late spermatids, which are under the control of Leydig cell‐derived testosterone.
Abstract: Selenium deficiency is known to be associated with male infertility, and the selenoprotein PHGPx has been shown to increase in rat testis after puberty and to depend on gonadotropin stimulation in hypophysectomized rats [Roveri et al. (1992) J. Biol. Chem. 267, 6142 6146]. Exposure of decapsulated whole testis, however, failed to reveal any transcriptional activation or inhibition of the PHGPx gene by testosterone, human chorionic gonadotropin, or forskolin. Nevertheless, it was verified that the specific activity of PHGPx in testis, but not of cGPx, correlated with sexual maturation. Leydig cell destruction in vivo by ethane dimethane sulfonate (EDS) resulted in a delayed decrease in PHGPx activity and mRNA that could be completely prevented by testosterone substitution. cGPx transiently increased upon EDS treatment, probably as a result of reactive macrophage augmentation. In situ mRNA hybridization studies demonstrated an uncharacteristic low level of cGPx transcription in testis, whereas PHGPx mRNA was abundantly and preferentially expressed in round spermatids. The data show that the age or gonadotropin-dependent expression of PHGPx in testis does not result from direct transcriptional gene activation by testosterone, but is due to differentiation stage-specific expression in late spermatids, which are under the control of Leydig cell-derived testosterone. The striking burst of PHGPx expression at the transition of round to elongated spermatids suggests an involvement of this selenoprotein in sperm maturation.

Journal ArticleDOI
TL;DR: Nkx5-1 is the first ear-specific molecule identified to play a crucial role in the formation of the mammalian vestibular system by inactivation of the homeobox gene by homologous recombination in mice.
Abstract: The inner ear develops from the otic vesicle, a one-cell-thick epithelium, which eventually transforms into highly complex structures including the sensory organs for balance (vestibulum) and hearing (cochlea). Several mouse inner ear mutations with hearing and balance defects have been described but for most the underlying genes have not been identified, for example, the genes controlling the development of the vestibular organs. Here, we report the inactivation of the homeobox gene, Nkx5-1, by homologous recombination in mice. This gene is expressed in vestibular structures throughout inner ear development. Mice carrying the Nkx5-1 null mutation exhibit behavioural abnormalities that resemble the typical hyperactivity and circling movements of the shaker/waltzer type mutants. The balance defect correlates with severe malformations of the vestibular organ in Nkx5-1(-/-) mutants, which fail to develop the semicircular canals. Nkx5-1 is the first ear-specific molecule identified to play a crucial role in the formation of the mammalian vestibular system.

Journal ArticleDOI
TL;DR: In this paper, the authors evaluated thirteen existing plants in six European countries and showed that the yearly solar gains of the systems are between 300 and 550 kWh per m2 collector area, while the investment cost of solar plants with short-term storage varies from 300 up to 600 ECU per m 2.

Journal ArticleDOI
TL;DR: The performance of the convolutional codes is analyzed for the two modulation techniques and a new metric is developed for soft decision decoding of DAPSK modulated signals.
Abstract: The multilevel modulation techniques of 64-quadrature amplitude modulation (QAM) and 64-differential amplitude and phase-shift keying (DAPSK) have been proposed in combination with the orthogonal frequency-division multiplexing (OFDM) scheme for digital terrestrial video broadcasting (DTVB). With this system a data rate of 34 Mb/s can be transmitted over an 8-MHz radio channel. A comparison of these modulation methods in the uncoded case has been presented by Engels and Rohling (see European Trans. Telecommun., vol.6, p.633-40, 1995). The channel coding scheme proposed for DTVB by Schafer (see Proc. Int. Broadcasting Convention, Amsterdam, The Netherlands, p.79-84, 1995) consists of an inner convolutional code concatenated with an outer Reed-Solomon (RS) code. In this paper the performance of the convolutional codes is analyzed for the two modulation techniques. This analysis includes soft decision Viterbi (1971) decoding of the convolutional code. For soft decision decoding of DAPSK modulated signals a new metric is developed.

Journal ArticleDOI
TL;DR: In this paper, the ground signatures of dynamic substorm features with particular emphasis on the event interpretation capabilities provided by the IMAGE magnetometer network were presented, and the authors stressed the importance of multi-instrument observation for a reliable interpretation of dynamic auroral processes.
Abstract: We present the ground signatures of dynamic substorm features with particular emphasis on the event interpretation capabilities provided by the IMAGE magnetometer network. This array covers the high latitudes from the sub-auroral to the cusp/cleft region. An isolated substorm on 11 Oct. 1993 during the late evening hours exhibited many of well-known features such as the Harang discontinuity, westward travelling surge and poleward leap, but also discrete auroral forms, known as auroral streamers, appeared propagating westward along the centre of the electrojet. Besides the magnetic field measurements, there were auroral observations and plasma flow and conductivity measurements obtained by EISCAT. The data of all three sets of instruments are consistent with the notion of upward field-aligned currents associated with the moving auroral patches. A detailed analysis of the electro-dynamic parameters in the ionosphere, however, reveals that they do not agree with the expectations resulting from commonly used simplifying approximations. For example, the westward moving auroral streamers which are associated with field-aligned current filaments, are not collocated with the centres of equivalent current vortices. Furthermore, there is a clear discrepancy between the measured plasma flow direction and the obtained equivalent current direction. All this suggests that steep conductivity gradients are associated with the transient auroral forms. Also self-induction effects in the ionosphere may play a role for the orientation of the plasma flows. This study stresses the importance of multi-instrument observation for a reliable interpretation of dynamic auroral processes.

Proceedings ArticleDOI
18 May 1998
TL;DR: It is shown that a orthogonal frequency division multiplexing system is technically equivalent to a single-carrier system with a guard interval if the columns of a Fourier matrix are used as spreading codes.
Abstract: The combination of orthogonal frequency division multiplexing (OFDM) and code division multiplexing (CDM) has found great interest. In contrast to a conventional OFDM system the information is spread over several subcarriers using orthogonal codes which leads to a diversity gain in frequency-selective channels. In this paper it is shown that such a system is technically equivalent to a single-carrier system with a guard interval if the columns of a Fourier matrix are used as spreading codes. The pros and cons of such a system compared to an OFDM-CDM system with arbitrary spreading matrix are described and discussed.

Journal ArticleDOI
TL;DR: The character of the mechanically induced structural disorder and nature of the metastability of mechanosynthesized zinc ferrite were elucidated by investigation of its structure in this paper, where the authors concentrated on the explanation of an origin of mechanically induced changes in magnetic properties of the nanoscale mechanoSynthesised ferrite.

Journal ArticleDOI
TL;DR: Fourteen Rhodobacter capsulatus mutants unable to grow with xanthine as sole nitrogen source were isolated by random Tn5 mutagenesis and revealed a higher degree of similarity to eukaryotic x anthine dehydrogenases than to the xanthin dehydrogenase‐related aldehyde oxidoreductase from Desulphovibrio gigas.
Abstract: Fourteen Rhodobacter capsulatus mutants unable to grow with xanthine as sole nitrogen source were isolated by random Tn5 mutagenesis. Five of these Tn5 insertions were mapped within two adjacent chromosomal EcoRI fragments hybridizing to oligonucleotides synthesized according to conserved amino acid sequences of eukaryotic xanthine dehydrogenases. DNA sequence analysis of this region revealed two open reading frames, designated xdhA and xdhB, encoding xanthine dehydrogenase. The deduced amino acid sequence of XDHA contains binding sites for two [2Fe-2S] clusters and FAD, whereas XDHB is predicted to contain the molybdopterin cofactor. In contrast to R. capsulatus, these three cofactor binding sites reside within a single polypeptide chain in eukaryotic xanthine dehydrogenases. The amino acid sequence of xanthine dehydrogenase from R. capsulatus showed a higher degree of similarity to eukaryotic xanthine dehydrogenases than to the xanthine dehydrogenase-related aldehyde oxidoreductase from Desulphovibrio gigas. The expression of an xdhA-lacZ fusion was induced when hypoxanthine or xanthine was added as sole nitrogen source. Mutations in nlfR1 (ntrC) and nifR4 (rpoN, encoding σ) had no influence on xdh gene expression. A putative activator sensing the availability of substrate seems to respond to xanthine but not to hypoxanthine. The transcriptional start site of xdhA was mapped by primer extension analysis. Comparison with known promoter elements revealed no significant homology. Xanthine dehydrogenase from R. capsulatus was purified to homogeneity. The enzyme consists of two subunits with molecular masses of 85 kDa and 50 kDa respectively. N-terminal amino acid sequencing of both subunits confirmed the predicted start codons. The molecular mass of the native enzyme was determined to be 275 kDa, indicating an αβ-subunit structure. Analysis of the molybdenum cofactor of xanthine dehydrogenase from R. capsulatus revealed that it contains the molybdopterin cofactor and not a molybdopterin dinucleotide derivative.

Journal ArticleDOI
TL;DR: In this paper, the authors studied how synchronization is initially established, using an experimental paradigm in which the metronome is activated after the subject has executed a series of self-paced finger taps.
Abstract: Most studies of synchronization have focused on how an established phase relationship between self-produced events (e.g., finger taps) and the clicks of a metronome is maintained when the metronome is regular or subject to unpredictable perturbations. Here we study how synchronization is initially established, using an experimental paradigm in which the metronome is activated after the subject has executed a series of self-paced finger taps. In Exp. 1, the metronome period was constant and equal to the mean of the self-paced inter-response intervals, whereas the initial phase difference of the metronome from the taps varied across trials. The synchronization error patterns could be predicted by a linear phase correction model. Experiment 2 involved both period and phase correction. The initial phase difference was constant, whereas the metronome period varied across trials. The observed synchronization error patterns suggest that the subjects achieved synchronization either by reacting to the second metronome signal or by aiming at the third metronome signal. The pattern of the residual synchronization errors was consistent with the linear phase correction model. These results support the notion that period and phase correction mechanisms are called for by different task variables and contribute differently to sensorimotor synchronization.

Journal Article
TL;DR: It is illustrated that only some aspects of gene expression and presumably pattern formation during inner ear development can be established and maintained ectopically and the dorsal vestibular structures seem to be programmed earlier and differently from the ventral cochlear part.
Abstract: The early stages of otic placode development depend on signals from neighbouring tissues including the hindbrain. The identity of these signals and of the responding placodal genes, however, is not known. We have identified a chick homeobox gene cNkx5-1, which is expressed in the otic placode beginning at stage 10 and exhibits a dynamic expression pattern during formation and further differentiation of the otic vesicle. In a series of heterotopic transplantation experiments, we demonstrate that cNkx5-1 can be activated in ectopic positions. However, significant differences in otic development and cNkx5-1 gene activity were observed when placodes were transplanted into the more rostral positions within the head mesenchyme or into the wing buds of older hosts. These results indicate that only the rostral tissues were able to induce and/or maintain ear development. Ectopically induced cNkx5-1 expression always reproduced the endogenous pattern within the lateral wall of the otocyst that is destined to form vestibular structures. In contrast, cPax2 which is expressed in the medial wall of the early otic vesicle later forming the cochlea never resumed its correct expression pattern after transplantation. Our experiments illustrate that only some aspects of gene expression and presumably pattern formation during inner ear development can be established and maintained ectopically. In particular, the dorsal vestibular structures seem to be programmed earlier and differently from the ventral cochlear part.

Journal ArticleDOI
TL;DR: Genomic Southern hybridizations show that Cyclops is abundant not only in pea but also in common bean, mung bean, broad bean, soybean and the pea nut suggesting that cyclops may be an useful genetic tool for analyzing the genomes of agronomically important legumes.
Abstract: We characterized a novel giant Gypsy-like retrotransposon, Cyclops, present in about 5000 copies in the genome of Pisum sativum The individual element Cyclops-2 measures 12 314 bp including long terminal repeats (LTRs) of 1504 bp and 1594 bp, respectively, showing 41% sequence divergence between one another Cyclops-2 carries a polypurine tract (PPT) and an unusual primer binding site (PBS) complementary to tRNA-Glu The element is bounded by 5 bp target site duplications and harbors three successive internal regions with homology to retroviral genes gag (424 codons) and pol (1382 codons) and an additional open reading frame (423 codons) of unknown function indicating the element's potential capacity for gene transduction The pol region contains sequence motifs related to the enzymes protease, reverse transcriptase, RNAse H and integrase in the same typical order (5′-PR-RT-RH-IN-3′) known for retroviruses and Gypsy-like retrotransposons The reading frame of the pol region is disrupted by several mutations suggesting that Cyclops-2 does not encode functional enzymes A phylogenetic analysis of the reverse transcriptase domain confirms our differential genetic assessment that Cyclops from pea is a novel element with no specific relationship to the previously described Gypsy-like elements from plants Genomic Southern hybridizations show that Cyclops is abundant not only in pea but also in common bean, mung bean, broad bean, soybean and the pea nut suggesting that Cyclops may be an useful genetic tool for analyzing the genomes of agronomically important legumes

Journal ArticleDOI
TL;DR: The dynamic expression pattern of Nkx2-9 in ventral domains of the CNS is consistent with a possible role in the specification of a distinct subset of neurons.

Journal ArticleDOI
TL;DR: The dynamic and periodically reiterated expression of cMeso-1 along theAnteroposterior axis is not dependent on anterior structures or the propagation of a signal along the anteropostior axis but seems to follow an intrinsic patterning program which is already set up in the segmental plate.

Journal ArticleDOI
TL;DR: In this article, a modified version of the original procedure by H.-W. Wanzlick et al. for the synthesis of the imidazolium salt starting material, 1 has now been isolated as a stable crystalline solid at room temperature.
Abstract: Questions remain as to why the title compound 1 was never isolated before; contrary to long-held opinion, this compound is not unstable. With a modified version of the original procedure by H.-W. Wanzlick et al. for the synthesis of the imidazolium salt starting material, 1 has now been isolated as a stable crystalline solid at room temperature.

Journal ArticleDOI
01 Feb 1998
TL;DR: In this article, a new wide slot antenna with capacitively coupled CPW feed and metallic strips in the apertures is presented, and numerical analysis is based on the Galerkin moment method in the spectral domain approach.
Abstract: A new wide slot antenna with capacitively coupled CPW-feed and metallic strips in the apertures is presented. The numerical analysis is based on the Galerkin moment method in the spectral domain approach. A simplified formula to calculate the input impedance is proposed. Theoretical and experimental results demonstrate the significant performance improvement of this modified structure. The influence of various design parameters is investigated. A 50% impedance bandwidth (SWR<2.0) and cross-polarisation levels below -20 dB are demonstrated.

Journal ArticleDOI
TL;DR: Abbreviations: bind.
Abstract: Abbreviations: bind., binding; Chl, Chlorella vulgaris ;C pa,Cyanophora paradoxa ;E pi, Epifagus virginiana; Eug, Euglena gracilis; hom., homologue; Mar, Marchantia polymorpha ; Nic, Nicotiana tabacum; Odo, Odontella sinensis ;O ry,Oryza sativa ;P in,Pinus thunbergii; Pla, Plasmodium falciparum ;P or,Porphyra purpurea; prot., protein; RT, reverse transcriptase; sim., similar to; SU, subunit; Syn, Synechocystis sp. PCC6803; Zea, Zea mays