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DICER-LIKE3 activity in Physcomitrella patens DICER-LIKE4 mutants causes severe developmental dysfunction and
M Asif Arif1, Isam Fattash, Zhaorong Ma
1Plant Biotechnology, University of Freiburg, Schaenzlestraβe 1, D-79104 Freiburg, Germany.
Molecular Plant
|April 19, 2012
Summary
Physcomitrella patens DICER-LIKE 4 (PpDCL4) is crucial for 21-nt ta-siRNA production. Loss of PpDCL4 causes developmental defects due to PpDCL3 activity, not PpDCL4 absence.
Area of Science:
- Plant molecular biology
- RNA interference pathways
- Small RNA biogenesis
Background:
- Trans-acting small interfering RNAs (ta-siRNAs) are plant-specific small RNAs regulating gene expression.
- ta-siRNAs are generated from TAS precursor transcripts through microRNA-guided cleavage and Dicer processing.
- ta-siRNAs function similarly to microRNAs (miRNAs) in directing target RNA cleavage.
Purpose of the Study:
- To investigate the role of Physcomitrella patens DICER-LIKE 4 (PpDCL4) in ta-siRNA biogenesis.
- To elucidate the cause of developmental abnormalities observed in PpDCL4 mutants.
- To identify novel ta-siRNA loci in Physcomitrella patens.
Main Methods:
- Gene knockout studies in Physcomitrella patens (ΔPpDCL4 and ΔPpDCL3/ΔPpDCL4 mutants).
- Analysis of small interfering RNA (siRNA) size distribution and accumulation.
- Identification and characterization of new ta-siRNA loci (TAS6).
Main Results:
- PpDCL4 is essential for producing 21-nt ta-siRNAs in Physcomitrella.
- Absence of PpDCL4 leads to accumulation of 23/24-nt ta-siRNAs due to PpDCL3 activity.
- Developmental defects in ΔPpDCL4 mutants are caused by PpDCL3 activity and are reversible.
- Discovery of new ta-siRNA loci, including the TAS6 family with specific miRNA target sites.
Conclusions:
- PpDCL3 activity, not the loss of PpDCL4, underlies the observed phenotypes in ΔPpDCL4 mutants.
- The study clarifies the distinct roles of DCL proteins in ta-siRNA pathway and plant development.
- Identification of TAS6 loci expands the known diversity of ta-siRNA pathways in plants.
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