A block in degradation of MHC class II-associated invariant chain correlates with a reduction in transport from endosome carrier vesicles to the prelysosome compartment

Invariant chain (Ii) associated with MHC class II molecule is processed proteolytically via several distinct intermediates during its intracellular transport through endosomal compartments. Leupeptin added to the culture medium blocks processing of Ii, prevents its dissociation from the class II molecules and leads to an intracellular accumulation of a 22 kDa intermediate form of Ii. We show here that leupeptin has a very general effect on protein transport in the endocytic pathway. When added to Mel Juso cells leupeptin reduces the transport of endocytosed material from multivesicular body-like, endosome carrier vesicles (ECV) to the prelysosomal compartment (late endosome) and leads to a concomitant increase in the number of ECV. Our results argue that one effect of leupeptin, related to antigen processing and presentation, is to block transport of antigen and/or MHC class II molecules to prelysosomal compartments

WEL Gene Bank: The National Gene Bank for German Crop Wild Relative Species

Die "Genbank Wildpflanzen für Ernährung und Landwirtschaft" (Genbank WEL) wurde 2009 als ein bundesweites Netzwerk gegründet, um die Nutzung wildlebender pflanzengenetischer Ressourcen in Deutschland zu sichern und deren Verfügbarkeit als Saatgut gewährleisten zu können. Wildpflanzen für Ernährung und Landwirtschaft (WEL-Arten, im englischen crop wild relatives) stellen mit mehr als 2.800 Arten einen beachtlichen Anteil der ca. 4.300 heimischen Farn- und Blütenpflanzen dar. Mit der Saatgutgenbank WEL wurde eine wertvolle Ressource für zukünftige Forschungsprojekte und Anwendungen in der Pflanzenzüchtung geschaffen, die derzeit über 4.500 Akzessionen von 272 WEL-Arten umfasst. An dem Netzwerk sind die Botanischen Gärten Berlin, Karlsruhe, Osnabrück und Regensburg sowie die Pädagogische Hochschule Karlsruhe beteiligt. Der WEL-Genbankbestand soll durch weitere Sammlungsaktivitäten ausgebaut werden. Aufgrund fehlender Finanzierungsmittel kann dies nicht zielgerichtet durchgeführt werden und es besteht dringender Handlungsbedarf zur Weiterentwicklung der WEL-Genbank.The German “Genbank für Wildpflanzen für Ernährung und Landwirtschaft” (WEL) is a gene bank for crop wild relatives for which the German term ‘WEL’ species has been coined. The WEL gene bank was established in 2009 as a national network to protect wild plant genetic resources in Germany to protect and ensure availability of WEL seed material. The 2,800 species of wild plants used for nutrition and agriculture (crop wild relatives) represent a substantial proportion of our native 4,300 fern and flowering plant species. The WEL gene bank project has produced a valuable resource for future research projects and for use in crop breeding. Participating in this network are the Botanical Gardens of Berlin, Karlsruhe, Osnabrück and Regensburg, as well as the Educational College of Karlsruhe. The WEL gene bank is under management of the Botanical Garden of Osnabrück, Germany. The Information and coordination centre of the Federal Office for Agriculture and Food (BLE) is responsible for the integration of the WEL gene bank in the “National Specialist Programme for Plant Genetic Resources” (PGDEU). There are currently 4,500 accessions of 272 species in the WEL gene bank. Currently no further funding is available, although the WEL gene bank needs further development

Conserved redox-dependent DNA binding of ROXY glutaredoxins with TGA transcription factors

peer-reviewedThe Arabidopsis thaliana CC‐type glutaredoxin (GRX) ROXY1 and the bZIP TGA transcription factor (TF) PERIANTHIA (PAN) interact in the nucleus and together regulate petal development. The CC‐type GRXs exist exclusively in land plants, and in contrast to the ubiquitously occurring CPYC and CGFS GRX classes, only the CC‐type GRXs expanded strongly during land plant evolution. Phylogenetic analyses show that TGA TFs evolved before the CC‐type GRXs in charophycean algae. MpROXY1/2 and MpTGA were isolated from the liverwort Marchantia polymorpha to analyze regulatory ROXY/TGA interactions in a basal land plant. Homologous and heterologous protein interaction studies demonstrate that nuclear ROXY/TGA interactions are conserved since the occurrence of CC‐type GRXs in bryophytes and mediated by a conserved ROXY C‐terminus. Redox EMSA analyses show a redox‐sensitive binding of MpTGA to the cis‐regulatory as‐1‐like element. Furthermore, we demonstrate that MpTGA binds together with MpROXY1/2 to this motif under reducing conditions, whereas this interaction is not observed under oxidizing conditions. Remarkably, heterologous complementation studies reveal a strongly conserved land plant ROXY activity, suggesting an ancestral role for CC‐type GRXs in modulating the activities of TGA TFs. Super‐resolution microscopy experiments detected a strong colocalization of ROXY1 with the active form of the RNA polymerase II in the nucleus. Together, these data shed new light on the function of ROXYs and TGA TFs and the evolution of redox‐sensitive transcription regulation processes, which likely contributed to adapt land plants to novel terrestrial habitats

The Naming of Names: Guidelines for Gene Nomenclature in Marchantia.

While Marchantia polymorpha has been utilized as a model system to investigate fundamental biological questions for over almost two centuries, there is renewed interest in M. polymorpha as a model genetic organism in the genomics era. Here we outline community guidelines for M. polymorpha gene and transgene nomenclature, and we anticipate that these guidelines will promote consistency and reduce both redundancy and confusion in the scientific literature

Insights into Land Plant Evolution Garnered from the Marchantia polymorpha Genome.

The evolution of land flora transformed the terrestrial environment. Land plants evolved from an ancestral charophycean alga from which they inherited developmental, biochemical, and cell biological attributes. Additional biochemical and physiological adaptations to land, and a life cycle with an alternation between multicellular haploid and diploid generations that facilitated efficient dispersal of desiccation tolerant spores, evolved in the ancestral land plant. We analyzed the genome of the liverwort Marchantia polymorpha, a member of a basal land plant lineage. Relative to charophycean algae, land plant genomes are characterized by genes encoding novel biochemical pathways, new phytohormone signaling pathways (notably auxin), expanded repertoires of signaling pathways, and increased diversity in some transcription factor families. Compared with other sequenced land plants, M. polymorpha exhibits low genetic redundancy in most regulatory pathways, with this portion of its genome resembling that predicted for the ancestral land plant. PAPERCLIP

Transformation of Riccia fluitans, an Amphibious Liverwort Dynamically Responding to Environmental Changes

The colonization of land by streptophyte algae, ancestors of embryophyte plants, was a fundamental event in the history of life on earth. Bryophytes are early diversifying land plants that mark the transition from freshwater to terrestrial ecosystems. The amphibious liverwort Riccia fluitans can thrive in aquatic and terrestrial environments and thus represents an ideal organism to investigate this major transition. Therefore, we aimed to establish a transformation protocol for R. fluitans to make it amenable for genetic analyses. An Agrobacterium transformation procedure using R. fluitans callus tissue allows to generate stably transformed plants within 10 weeks. Furthermore, for comprehensive studies spanning all life stages, we demonstrate that the switch from vegetative to reproductive development can be induced by both flooding and poor nutrient availability. Interestingly, a single R. fluitans plant can consecutively adapt to different growth environments and forms distinctive and reversible features of the thallus, photosynthetically active tissue that is thus functionally similar to leaves of vascular plants. The morphological plasticity affecting vegetative growth, air pore formation, and rhizoid development realized by one genotype in response to two different environments makes R. fluitans ideal to study the adaptive molecular mechanisms enabling the colonialization of land by aquatic plants

The N-Terminus of the Floral Arabidopsis TGA Transcription Factor PERIANTHIA Mediates Redox-Sensitive DNA-Binding.

The Arabidopsis TGA transcription factor (TF) PERIANTHIA (PAN) regulates the formation of the floral organ primordia as revealed by the pan mutant forming an abnormal pentamerous arrangement of the outer three floral whorls. The Arabidopsis TGA bZIP TF family comprises 10 members, of which PAN and TGA9/10 control flower developmental processes and TGA1/2/5/6 participate in stress-responses. For the TGA1 protein it was shown that several cysteines can be redox-dependently modified. TGA proteins interact in the nucleus with land plant-specific glutaredoxins, which may alter their activities posttranslationally. Here, we investigated the DNA-binding of PAN to the AAGAAT motif under different redox-conditions. The AAGAAT motif is localized in the second intron of the floral homeotic regulator AGAMOUS (AG), which controls stamen and carpel development as well as floral determinacy. Whereas PAN protein binds to this regulatory cis-element under reducing conditions, the interaction is strongly reduced under oxidizing conditions in EMSA studies. The redox-sensitive DNA-binding is mediated via a special PAN N-terminus, which is not present in other Arabidopsis TGA TFs and comprises five cysteines. Two N-terminal PAN cysteines, Cys68 and Cys87, were shown to form a disulfide bridge and Cys340, localized in a C-terminal putative transactivation domain, can be S-glutathionylated. Comparative land plant analyses revealed that the AAGAAT motif exists in asterid and rosid plant species. TGA TFs with N-terminal extensions of variable length were identified in all analyzed seed plants. However, a PAN-like N-terminus exists only in the rosids and exclusively Brassicaceae homologs comprise four to five of the PAN N-terminal cysteines. Redox-dependent modifications of TGA cysteines are known to regulate the activity of stress-related TGA TFs. Here, we show that the N-terminal PAN cysteines participate in a redox-dependent control of the PAN interaction with a highly conserved regulatory AG cis-element, emphasizing the importance of redox-modifications in the regulation of flower developmental processes

Evolution of the N-terminal PAN extension and the <i>AAGAAT</i> motif.

<p>Cladogram of evolutionary informative species from seed plants indicating <i>AAGAAT</i> motifs and N-terminal extensions of the respective PAN and <i>AG</i> homologs. Orange boxes indicate presence of an <i>AAGAAT</i> motif comprising the AAGAAT sequence and core TGA binding site. Beige boxes label partial <i>AAGAAT</i> motifs, which possess only the AAGAAT sequence and lack the core TGA binding sequence TGACG. Schematic representation of PAN protein homologs shows N-terminal extensions with significant (grey bar) or low sequence homology (striped bar) to the PAN N-terminus or its absence. Presence (C) or absence (X) of cysteines equivalent to the five N-terminal PAN cysteines is depicted. Stars indicate that the definition of a magnoliid PAN homolog start codon was not possible and that no genome sequencing data were available.</p