RESUMEN
BACKGROUND: Volvox carteri (V. carteri) is a multicellular green alga used as model system for the evolution of multicellularity. So far, the contribution of small RNA pathways to these phenomena is not understood. Thus, we have sequenced V. carteri Argonaute 3 (VcAGO3)-associated small RNAs from different developmental stages. RESULTS: Using this functional approach, we define the Volvox microRNA (miRNA) repertoire and show that miRNAs are not conserved in the closely related unicellular alga Chlamydomonas reinhardtii. Furthermore, we find that miRNAs are differentially expressed during different life stages of V. carteri. In addition to miRNAs, transposon-associated small RNAs or phased siRNA loci, which are common in higher land plants, are highly abundant in Volvox as well. Transposons not only give rise to miRNAs and other small RNAs, they are also targets of small RNAs. CONCLUSION: Our analyses reveal a surprisingly complex small RNA network in Volvox as elaborate as in higher land plants. At least the identified VcAGO3-associated miRNAs are not conserved in C. reinhardtii suggesting fast evolution of small RNA systems. Thus, distinct small RNAs may contribute to multicellularity and also division of labor in reproductive and somatic cells.
Asunto(s)
Evolución Molecular , Regulación de la Expresión Génica de las Plantas , Silenciador del Gen , ARN Pequeño no Traducido/genética , Volvox/genética , Proteínas Argonautas/metabolismo , Secuencia de Bases , Sitios de Unión , Biología Computacional/métodos , Elementos Transponibles de ADN , Perfilación de la Expresión Génica , MicroARNs/genética , Anotación de Secuencia Molecular , Motivos de Nucleótidos , Unión Proteica , Reproducibilidad de los Resultados , TranscriptomaAsunto(s)
Biotecnología/métodos , Lisina/química , Péptidos/química , Dióxido de Silicio/química , Secuencia de Aminoácidos , Cromatina/metabolismo , Diatomeas , Modelos Químicos , Datos de Secuencia Molecular , Mapeo Peptídico , Polímeros/química , Ingeniería de Proteínas , Estructura Terciaria de Proteína , Proteínas Protozoarias/química , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Estrés MecánicoAsunto(s)
Proteínas/química , Compuestos de Amonio Cuaternario/química , Dióxido de Silicio/química , Animales , Diatomeas/química , Péptidos/química , Conformación Proteica , Espectrometría de Masa por Ionización de Electrospray/métodos , Espectrometría de Masa por Ionización de Electrospray/normasRESUMEN
The alga Volvox carteri is one of the simplest multicellular organisms, yet it has a surprisingly complex extracellular matrix (ECM), making Volvox suitable as a model system in which to study ECM self-assembly. Here, we analyze the primary structures and post-translational modifications of two main ECM components synthesized in response to sexual induction as well as wounding. These proteins are members of the pherophorin family with as yet unknown properties. They contain polyhydroxyproline spacers as long as 500 and 2750 residues. Even the highly purified proteins retain the capacity to self-assemble and cross-link, producing an insoluble fibrous network in an apparently autocatalytic reaction. This pherophorin-based network is located within the deep zone of the ECM. A molecular genetic search for additional members of the pherophorin family indicates that at least nine different pherophorin species can be expected to serve as precursors for ECM substructures. Therefore, the highly diversified members of the pherophorin family represent region-specific morphological building blocks for ECM assembly and cross-linking.
