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Publikationen - Molekulare Signalverarbeitung

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Publikation

Asquini, E.; Gerdol, M.; Gasperini, D.; Igic, B.; Graziosi, G.; Pallavicini, A.; S-RNase-like Sequences in Styles of Coffea (Rubiaceae). Evidence for S-RNase Based Gametophytic Self-Incompatibility? Trop. Plant Biol. 4, 237-249, (2011) DOI: 10.1007/s12042-011-9085-2

Although RNase-based self-incompatibility (SI) is suspected to operate in a wide group of plant families, it has been characterized as the molecular genetic basis of SI in only three distantly related families, Solanaceae, Plantaginaceae, and Rosaceae, all described over a decade ago. Previous studies found that gametophytic SI, controlled by a multi-allelic S-locus, operates in the coffee family (Rubiaceae). The molecular genetic basis of this mechanism remains unknown, despite the immense importance of coffee as an agricultural commodity. Here, we isolated ten sequences with features of T2-S-type RNases from two Coffea species. While three of the sequences were identified in both species and clearly do not appear to be S-locus products, our data suggest that six sequences may be S-alleles in the self-incompatible C. canephora, and one may be a relict in the self-compatible C. arabica. We demonstrate that these sequences show style-specific expression, display polymorphism in C. canephora, and cluster with S-locus products in a phylogenetic analysis that includes other plant families with RNase-based SI. Although our results are not definitive, in part because the available plant materials were limited and data patterns relatively complex, our results strongly hint that RNase-based SI mechanism operates in the Rubiaceae family.
Publikation

Flores, R.; Grubb, D.; Elleuch, A.; Nohales, M.-?.; Delgado, S.; Gago, S.; Rolling-circle replication of viroids, viroid-like satellite RNAs and hepatitis delta virus: Variations on a theme RNA Biol. 8, 200-206, (2011) DOI: 10.4161/rna.8.2.14238

Viroids and viroid-like satellite RNAs from plants, and the human hepatitis delta virus (HDV) RNA share some properties that include small size, circularity and replication through a rolling-circle mechanism. Replication occurs in different cell compartments (nucleus, chloroplast and membrane-associated cytoplasmatic vesicles) and has three steps: RNA polymerization, cleavage and ligation. The first step generates oligomeric RNAs that result from the reiterative transcription of the circular templates of one or both polarities, and is catalyzed by either the RNA-dependent RNA polymerase of the helper virus on which viroid-like satellite RNAs are functionally dependent, or by host DNA-dependent RNA polymerases that, remarkably, viroids and HDV redirect to transcribe RNA templates. Cleavage is mediated by host enzymes in certain viroids and viroid-like satellite RNAs, while in others and in HDV is mediated by cis-acting ribozymes of three classes. Ligation appears to be catalyzed mainly by host enzymes. Replication most likely also involves many other non-catalytic proteins of host origin and, in HDV, the single virus-encoded protein.
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