title: A single dicer gene is required for efficient gene silencing associated with two classes of small antisense RNAs in Mucor circinelloides.
abstract: RNA silencing in the zygomycete Mucor circinelloides exhibits uncommon features, such as induction by self-replicative sense transgenes and the accumulation of two size classes of antisense small interfering RNAs (siRNAs). To investigate whether this silencing phenomenon follows the rules of a canonical RNA-silencing mechanism, we used hairpin RNA (hpRNA)-producing constructs as silencing triggers and analyzed the efficiency and stability of silencing in different genetic backgrounds. We show here that the dsRNA-induced silencing mechanism is also associated with the accumulation of two sizes of antisense siRNAs and that this mechanism is not mediated by the previously known dcl-1 (dicer-like) gene, which implies the existence of an additional dicer gene. An M. circinelloides dcl-2 gene was cloned and characterized, and the corresponding null mutant was generated by gene replacement. This mutant is severely impaired in the silencing mechanism induced by self-replicative sense or inverted-repeat transgenes, providing the first genetic evidence of a canonical silencing mechanism in this class of fungus and pointing to a role for dcl-2 in the mechanism. Moreover, a functional dcl-2 gene is required for the normal accumulation of the two sizes of antisense RNAs, as deduced from the analysis of dcl-2(-) transformants containing hpRNA-expressing plasmids. In addition to its critical role in transgene-induced silencing, the dcl-2 gene seems to play a role in the control of vegetative development, since the dcl-2 null mutants showed a significant decrease in their production of asexual spores.
authors: Departamento de Genética y Microbiología, Facultad de Biología, Universidad de Murcia, 30100 Murcia, Spain. rmruiz@um.es.
authors: Juan P
authors: JP
authors: de Haro
authors: Silvia
authors: S
authors: Calo
authors: María
authors: M
authors: Cervantes
authors: Francisco E
authors: FE
authors: Nicolás
authors: Santiago
authors: S
authors: Torres-Martínez
authors: Rosa M
authors: RM
authors: Ruiz-Vázquez
mesh_terms: D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D009089:Mucor / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D034622:RNA Interference; D016372:RNA, Antisense / Q000378:metabolism*; D012331:RNA, Fungal / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism*; D043244:Ribonuclease III / Q000235:genetics* / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D016372:RNA, Antisense; D012331:RNA, Fungal; D034741:RNA, Small Interfering; D043244:Ribonuclease III