Abstract

Unlike in Arabidopsis, loss of function of Polymerase IV in the Brassicaceae species Capsella rubella causes microspore arrest, revealing an important role for Polymerase IV in pollen development.In Arabidopsis (Arabidopsis thaliana), DNA-dependent RNA polymerase IV (Pol IV) is required for the formation of transposable element (TE)-derived small RNA transcripts. These transcripts are processed by DICER-LIKE3 into 24-nucleotide small interfering RNAs (siRNAs) that guide RNA-directed DNA methylation. In the pollen grain, Pol IV is also required for the accumulation of 21/22-nucleotide epigenetically activated siRNAs, which likely silence TEs via post-transcriptional mechanisms. Despite this proposed role of Pol IV, its loss of function in Arabidopsis does not cause a discernible pollen defect. Here, we show that the knockout of NRPD1, encoding the largest subunit of Pol IV, in the Brassicaceae species Capsella (Capsella rubella), caused postmeiotic arrest of pollen development at the microspore stage. As in Arabidopsis, all TE-derived siRNAs were depleted in Capsella nrpd1 microspores. In the wild-type background, the same TEs produced 21/22-nucleotide and 24-nucleotide siRNAs; these processes required Pol IV activity. Arrest of Capsella nrpd1 microspores was accompanied by the deregulation of genes targeted by Pol IV-dependent siRNAs. TEs were much closer to genes in Capsella compared with Arabidopsis, perhaps explaining the essential role of Pol IV in pollen development in Capsella. Our discovery that Pol IV is functionally required in Capsella microspores emphasizes the relevance of investigating different plant models.

Published in

Plant Cell
2020, Volume: 32, number: 4, pages: 950-966
Publisher: AMER SOC PLANT BIOLOGISTS

SLU Authors

• Wang, Zhenxing

  • Department of Plant Biology, Swedish University of Agricultural Sciences
    

• Butel, Nicolas

  • Department of Plant Biology, Swedish University of Agricultural Sciences
    

• Santos-González, Juan

  • Department of Plant Biology, Swedish University of Agricultural Sciences
    

• Yi, Jun

  • Department of Plant Biology, Swedish University of Agricultural Sciences
    

• Martinez-Arias, Germán

  • Department of Plant Biology, Swedish University of Agricultural Sciences
    

• Köhler, Claudia

  • Department of Plant Biology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Agricultural Science
Cell Biology


Publication identifier

DOI: https://doi.org/10.1105/tpc.19.00938

Permanent link to this page (URI)

https://res.slu.se/id/publ/105731