Hammond T M, Keller N P
Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin 53706, USA.
Genetics. 2005 Feb;169(2):607-17. doi: 10.1534/genetics.104.035964. Epub 2004 Nov 15.
The versatility of RNA-dependent RNA polymerases (RDRPs) in eukaryotic gene silencing is perhaps best illustrated in the kingdom Fungi. Biochemical and genetic studies of Schizosaccharomyces pombe and Neurospora crassa show that these types of enzymes are involved in a number of fundamental gene-silencing processes, including heterochromatin regulation and RNA silencing in S. pombe and meiotic silencing and RNA silencing in N. crassa. Here we show that Aspergillus nidulans, another model fungus, does not require an RDRP for inverted repeat transgene (IRT)-induced RNA silencing. However, RDRP requirements may vary within the Aspergillus genus as genomic analysis indicates that A. nidulans, but not A. fumigatus or A. oryzae, has lost a QDE-1 ortholog, an RDRP associated with RNA silencing in N. crassa. We also provide evidence suggesting that 5' --> 3' transitive RNA silencing is not a significant aspect of A. nidulans IRT-RNA silencing. These results indicate a lack of conserved kingdom-wide requirements for RDRPs in fungal RNA silencing.
RNA依赖的RNA聚合酶（RDRP）在真核生物基因沉默中的多功能性在真菌界或许体现得最为淋漓尽致。对粟酒裂殖酵母和粗糙脉孢菌的生化及遗传学研究表明，这类酶参与了许多基本的基因沉默过程，包括粟酒裂殖酵母中的异染色质调控和RNA沉默，以及粗糙脉孢菌中的减数分裂沉默和RNA沉默。在此我们表明，另一种模式真菌构巢曲霉在反向重复转基因（IRT）诱导的RNA沉默中并不需要RDRP。然而，由于基因组分析表明构巢曲霉而非烟曲霉或米曲霉已经失去了QDE - 1直系同源基因（一种与粗糙脉孢菌RNA沉默相关的RDRP），RDRP的需求在曲霉属内可能存在差异。我们还提供了证据表明5'→3'传递性RNA沉默并非构巢曲霉IRT - RNA沉默的一个重要方面。这些结果表明，真菌RNA沉默中对RDRP缺乏全界保守的需求。
