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Wolf S.,French National Institute for Agricultural Research | Greiner S.,Center for Organismal Studies Heidelberg
Protoplasma | Year: 2012

Plant cell growth is controlled by the balance between turgor pressure and the extensibility of the cell wall. Several distinct classes of wall polysaccharides and their interactions contribute to the architecture and the emergent features of the wall. As a result, remarkable tensile strength is achieved without relinquishing extensibility. The control of growth and development does not only require a precisely regulated biosynthesis of cell wall components, but also constant remodeling and modification after deposition of the polymers. This is especially evident given the fact that wall deposition and cell expansion are largely uncoupled. Pectins form a functionally and structurally diverse class of galacturonic acid-rich polysaccharides which can undergo abundant modification with a concomitant change in physicochemical properties. This review focuses on homogalacturonan demethylesterification catalyzed by the ubiquitous enzyme pectin methylesterase (PME) as a growth control module. Special attention is drawn to the recently discovered role of this process in primordial development in the shoot apical meristem. © 2012 Springer-Verlag.


Wolf S.,Center for Organismal Studies Heidelberg | Hofte H.,French National Institute for Agricultural Research
Plant Cell | Year: 2014

Despite an increasingly detailed understanding of endogenous and environmental growth-controlling signals and their signaling networks, little is known on how these networks are integrated with the cell expansion machinery. Members of the CrRLK1L family control cell wall properties and cell expansion in a variety of developmental and environmental contexts. Two recent reports provide exciting new insights into the mode of action of these RLKs. One study shows that one family member, FERONIA (FER), is required for the production of hydroxyl radicals in the female gametophyte, which causes pollen tube rupture and sperm cell release during fertilization. Another study shows that FER is a receptor for a signaling peptide (Rapid Alkalinization Factor 1 [RALF1]) that triggers cell wall alkalinization and growth arrest, possibly through the inhibition of plasma membrane H+-ATPase activity. RALF1 belongs to a large gene family, with a wide range of expression patterns. Other CrRLK1L family members therefore may also be receptors for RALF-like peptides. These findings have important implications for our understanding of the control of cell wall integrity during growth and raise new intriguing questions. © 2014 American Society of Plant Biologists. All rights reserved.


Mau M.,Leibniz Institute of Plant Genetics and Crop Plant Research | Lovell J.T.,University of Texas at Austin | Corral J.M.,Coburg University of Applied Sciences | Kiefer C.,Max Planck Institute for Plant Breeding Research | And 4 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2015

Asexual reproduction is expected to reduce the adaptive potential to novel or changing environmental conditions, restricting or altering the ecological niche of asexual lineages. Asexual lineages of plants and animals are typically polyploid, an attribute that may influence their genetic variation, plasticity, adaptive potential, and niche breadth. The genus Boechera (Brassicaceae) represents an ideal model to test the relative ecological and biogeographic impacts of reproductive mode and ploidy because it is composed of diploid sexual and both diploid and polyploid asexual (i.e., apomictic) lineages. Here, we demonstrate a strong association between a transcriptionally conserved allele and apomictic seed formation. We then use this allele as a proxy apomixis marker in 1,649 accessions to demonstrate that apomixis is likely to be a common feature across the Boechera phylogeny. Phylogeographic analyses of these data demonstrate (i) species-specific niche differentiation in sexuals, (ii) extensive niche conservation between differing reproductive modes of the same species, (iii) ploidy-specific niche differentiation within and among species, and (iv) occasional niche drift between apomicts and their sexual ancestors. We conclude that ploidy is a substantially stronger and more common driver of niche divergence within and across Boechera species although variation in both traits may not necessarily lead to niche evolution on the species scale. © 2015, National Academy of Sciences. All rights reserved.


Mikosch M.,Center for Organismal Studies Heidelberg
Photosynthesis research | Year: 2012

The Fabaceae tree Butea monosperma (TAUB.; syn. Erythrina monosperma (LAM.)) is widely distributed in Central and West-India. We studied it at three sites, i.e. at two locations with contrasting exposure (NE and SW, respectively) in a small mountain range with poor soil on highly drained rocky slopes and at a third location in a plane with deeper soils and better water supply. The two mountain range sites differed in the light climate where the NE-slope obtained more day-integrated irradiance. Chlorophyll fluorescence was measured with a portable fluorometer and leaf samples for stable isotope analyses (δ(13)C, δ(15)N, δ(18)O) were collected. No differences were seen in carbon and nitrogen contents of leaves at the three sites. N and O isotope signatures of the leaves were similar at the two rocky hill slope sites. More positive values for both signatures were obtained in the leaves in the plane. For all sites saturation of ETR was only achieved well above a PPFD of 1,000 μmol m(-2) s(-1) indicating that the leaves were sun-type leaves. The photosynthetic performance of Butea at the plane was very similar to that at the SW-slope of the mountain range and higher ETRs were obtained at the NE-slope. Ecophysiological flexibility allows Butea to perform well in a variety of habitats and yet gives it particular fitness at specific sites. The best performance was observed in the highly insolated steep rocky hill site (NE-slope) underlining the suitability of the tree for reforestation.


Famatinanthus, a recently established monotypic genus, has a unique style type with a cobblestone-like surface. These cobblestonelike units comprise several epidermal cells that often have periclinal walls, resulting in a partially "double epidermis." The particular epidermis supports the exclusion from the genus Aphyllocladus (based on morphological data) as well as the elevation of the genus Famatinanthus to tribe and subfamily rank (based on chloroplast DNA data). To demonstrate the uniqueness of the stylar morphology of Famatinanthus, its styles and those of the remaining four species of Aphyllocladus were studied by SEM and histological sections. In addition, representatives of the basal tribes that share non-stylar characters with Famatinanthus, namely Gochnatieae, Hyalideae, Onoserideae, and Stifftieae, were studied in comparison. Due to the lack of stylar hairs, Famatinanthus is clearly distinct from Aphyllocladus, Onoseris (Onoserideae), and Hyaloseris (Stifftieae), which have stylar hairs on the entire dorsal side or only on the upper part of the stylar branches. Famatinanthus shares the glabrous stylar surface with Gochnatieae and Hyalideae, but in the latter tribes the rounded stylar branches are dorsally thickened (Gochnatia style type). A partially "double epidermis" can episodically be observed in the genus Stifftia, which has not been previously mentioned as a relative of Famatinanthus. The extensive sclerenchymatic tissue present in the stylar branches of Famatinanthus, however, is not found in Stifftia. © 2016 by the American Society of Plant Taxonomists.


Centanin L.,Center for Organismal Studies Heidelberg | Wittbrodt J.,Center for Organismal Studies Heidelberg
Development (Cambridge) | Year: 2014

A unique feature of humans is the complexity of our central nervous system. A fully functional brain requires that billions of neurons make specific contacts in a highly coordinated way, an issue that is still not well understood. The neural retina constitutes an excellent system with which to analyze key aspects of neurogenesis and circuit formation in the central nervous system. Here, we provide an overview of retinal neurogenesis in vertebrates and discuss implications of the developmental mechanisms involved for regenerative therapy approaches. © 2014. Published by The Company of Biologists Ltd.


Erbar C.,Center for Organismal Studies Heidelberg | Leins P.,Center for Organismal Studies Heidelberg
International Journal of Plant Sciences | Year: 2015

Premise of research. In the course of a detailed comparative study concerning style morphology (including 395 species of 258 genera covering all 44 tribes of the Asteraceae), we found a new microstructural feature, namely, often conspicuous cuticular patterns on the stylar hairs (involved in secondary pollen presentation) and stylar appendages. The observations raised questions as to whether the different striation patterns can be arranged in structural types and whether this new microcharacter could be of value in phylogenetic considerations. Methodology. Styles from liquid-preserved flowers or from herbarium material were studied by using scanning electron microscopy. Pivotal results. Five different patterns of cuticular striation can be discerned: crested pattern, triple pattern, double pattern, longitudinal pattern, and transverse pattern. By plotting the different cuticular patterns onto a generalized phylogenetic tree based on molecular data, it becomes obvious that there is considerable homoplasy in these features. Nevertheless, the cuticular patterns are still useful in characterizing some clades within the family. It is noteworthy that the small monogeneric subfamily Corymbioideae is characterized by a particular triple cuticular pattern on the stylar hairs that is otherwise found only rarely and isolated in some tribes (namely Mutisieae, Helenieae, Coreopsideae, and Heliantheae). The subfamily Mutisioideae is remarkable in the absence of simple patterns. A crested cuticular pattern is found only within the Mutisioideae (in Onoserideae and Mutisieae). Quite diverse in their cuticular patterns are the tribes Helenieae and Heliantheae within the Asteroideae. Conclusions. In comparison with the known influence of cuticular microstructures of petal cells on the wettability, we speculate that the cuticular striations of the stylar hairs increase the repellence of water drops in the flower, which would harm the viability of the pollen grains (due to osmosis, most pollen grains burst in pure water). © 2015 by The University of Chicago. All rights reserved.


Knezevic P.,University of Novi Sad | Curcin S.,Center for Organismal Studies Heidelberg | Aleksic V.,University of Novi Sad | Petrusic M.,University of Novi Sad | Vlaski L.,University of Novi Sad
Research in Microbiology | Year: 2013

Pseudomonas aeruginosa is a highly resistant opportunistic pathogen and an important etiological agent of various types of infections. During the last decade, P. aeruginosa phages have been extensively examined as alternative antimicrobial agents. The aim of the study was to determine antimicrobial effectiveness of combining subinhibitory concentrations of gentamicin, ceftriaxone, ciprofloxacin or polymyxin B with P. aeruginosa-specific bacteriophages belonging to families Podoviridae and Siphoviridae. The time-kill curve method showed that a combination of bacteriophages and subinhibitory concentrations of ceftriaxone generally reduced bacterial growth, and synergism was proven for a Siphoviridae phage σ-1 after 300 min of incubation. The detected alteration in morphology after ceftriaxone application, resulting in cell elongation, along with its specific mode of action, seemed to be a necessary but was not a sufficient reason for phage-antibiotic synergism. The phenomenon offers an opportunity for future development of treatment strategies for potentially lethal infections caused by P. aeruginosa. © 2012 Institut Pasteur.


Erbar C.,Center for Organismal Studies Heidelberg
Systematic Botany | Year: 2015

Bi- (to tri-) seriate stylar sweeping hairs are well-known from both genera (Eremothamnus, Hoplophyllum) of Eremothamneae (Asteraceae-Cichorioideae), and their assumed exclusive occurrence has been used in defining the tribe. In order to proof the phylogenetic/ taxonomic relevance of this character, I comprehensively studied genera of all tribes with respect to the occurrence of multi-seriate hairs. I describe for the first time bi- to even multi-seriate stylar hairs in the Hyaloseris clade (Stifftioideae-Stifftieae), in Oldenburgieae (Carduoideae), and in Wunderlichieae (Wunderlichioideae), formerly placed in a broadly circumscribed Mutisieae. The clusters of two to variable numbers of hairs, tightly linked together by their longitudinal cell walls, differ in the length of the tips of the individual cells, which remain separate during ontogeny and in the extent to which they cover the stylar branches and the stylar shaft. Stifftia exhibits papillate epidermal cells at the dorsal flanks of the stylar branches arranged in a line. On the basis of this observation, one can imagine that bi- to multi-seriate hairs result, if the walls of adjacent cells remain tightly linked during further elongation growth. Although the bi- to multi-seriate hairs are homoplasious, such hairs are not found in sister clades. Depending on their length and location on the styles, the bi- to multi-seriate stylar hairs are involved either in a brushing mechanism, in a pump mechanism, or in a combination of a brushing and a deposition mechanism of secondary pollen presentation. © Copyright 2015 by the American Society of Plant Taxonomists.


Dalakouras A.,AlPlanta Institute for Plant Research | Wassenegger M.,AlPlanta Institute for Plant Research | Wassenegger M.,Center for Organismal Studies Heidelberg
RNA Biology | Year: 2013

RNA-directed DNA methylation (RdDM) involves sequence-specific guiding of the de novo methylation machinery to complementary genomic DNA by RNA molecules. It is still elusive whether guide RNAs bind directly to DNA or to nascent transcripts produced from it. Even the nature of the guide RNAs is not elucidated. RNA interference (RNAi) studies provided a link between RNAi and RdDM indicating that small interfering RNAs (siRNAs) trigger and guide cytosine methylation. The "siRNA hypothesis" is generally accepted. However, recent data demonstrated that RdDM is not always associated with the accumulation of corresponding siRNAs. RdDM triggers may differ from guide RNAs and further studies are needed to clarify if guide RNAs are small or long RNAs, if they are single or double stranded and if they target DNA or nascent transcript. © 2013 Landes Bioscience.

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