title: DICER-LIKE3 activity in Physcomitrella patens DICER-LIKE4 mutants causes severe developmental dysfunction and sterility.
abstract: Trans-acting small interfering RNAs (ta-siRNAs) are plant-specific siRNAs released from TAS precursor transcripts after microRNA-dependent cleavage, conversion into double-stranded RNA, and Dicer-dependent phased processing. Like microRNAs (miRNAs), ta-siRNAs direct site-specific cleavage of target RNAs at sites of extensive complementarity. Here, we show that the DICER-LIKE 4 protein of Physcomitrella patens (PpDCL4) is essential for the biogenesis of 21 nucleotide (nt) ta-siRNAs. In ΔPpDCL4 mutants, off-sized 23 and 24-nt ta-siRNAs accumulated as the result of PpDCL3 activity. ΔPpDCL4 mutants display severe abnormalities throughout Physcomitrella development, including sterility, that were fully reversed in ΔPpDCL3/ΔPpDCL4 double-mutant plants. Therefore, PpDCL3 activity, not loss of PpDCL4 function per se, is the cause of the ΔPpDCL4 phenotypes. Additionally, we describe several new Physcomitrella trans-acting siRNA loci, three of which belong to a new family, TAS6. TAS6 loci are typified by sliced miR156 and miR529 target sites and are in close proximity to PpTAS3 loci.
authors.affiliation: Plant Biotechnology, University of Freiburg, Schaenzlestraβe 1, D-79104 Freiburg, Germany.
authors.forename: M Asif
authors.initials: MA
authors.lastname: Arif
authors.forename: Isam
authors.initials: I
authors.lastname: Fattash
authors.forename: Zhaorong
authors.initials: Z
authors.lastname: Ma
authors.forename: Sung Hyun
authors.initials: SH
authors.lastname: Cho
authors.forename: Anna K
authors.initials: AK
authors.lastname: Beike
authors.forename: Ralf
authors.initials: R
authors.lastname: Reski
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Axtell
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Frank
mesh_terms: D001483:Base Sequence; D019068:Bryopsida / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D056426:Genetic Loci / Q000235:genetics; D023281:Genomics; D035683:MicroRNAs / Q000235:genetics; D009154:Mutation; D010641:Phenotype; D051479:Plant Infertility / Q000235:genetics*; D034741:RNA, Small Interfering / Q000096:biosynthesis; D043244:Ribonuclease III / Q000235:genetics* / Q000378:metabolism*
chemical_list: D035683:MicroRNAs; D034741:RNA, Small Interfering; D043244:Ribonuclease III