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Discrimintion and Mapping of the Primary and Processed Transcripts in Maize Mitochondrion Using a Circular RT-PCR-based Strategy
Published on: July 29, 2019
Plant mitochondrial polyadenylated mRNAs are degraded by a 3'- to 5'-exoribonuclease activity, which proceeds
D Gagliardi1, R Perrin, L Marechal-Drouard
1Institut de Biologie Moléculaire des Plantes, CNRS, 12 rue du Général Zimmer, 67084 Strasbourg Cedex, France. dominique.gagliardi@ibmp-ulp.u-strasbg.fr
Abstract:
Recently, we and others have reported that mRNAs may be polyadenylated in plant mitochondria, and that polyadenylation accelerates the degradation rate of mRNAs. To further characterize the molecular mechanisms involved in plant mitochondrial mRNA degradation, we have analyzed the polyadenylation and degradation processes of potato atp9 mRNAs. The overall majority of polyadenylation sites of potato atp9 mRNAs is located at or in the vicinity of their mature 3'-extremities. We show that a 3'- to 5'-exoribonuclease activity is responsible for the preferential degradation of polyadenylated mRNAs as compared with non-polyadenylated mRNAs, and that 20-30 adenosine residues constitute the optimal poly(A) tail size for inducing degradation of RNA substrates in vitro. The addition of as few as seven non-adenosine nucleotides 3' to the poly(A) tail is sufficient to almost completely inhibit the in vitro degradation of the RNA substrate. Interestingly, the exoribonuclease activity proceeds unimpeded by stable secondary structures present in RNA substrates. From these results, we propose that in plant mitochondria, poly(A) tails added at the 3' ends of mRNAs promote an efficient 3'- to 5'- degradation process.
Insights
Plant mitochondria polyadenylation of messenger RNAs (mRNAs) accelerates their degradation. A 3’ to 5’ exoribonuclease activity preferentially degrades polyadenylated mRNAs, with optimal degradation occurring with 20-30 adenosine residues.
Area of Science:
- Molecular Biology
- Plant Science
- Biochemistry
Background:
- Messenger RNAs (mRNAs) in plant mitochondria can undergo polyadenylation.
- Polyadenylation has been observed to increase the rate of mRNA degradation.
Purpose of the Study:
- To investigate the molecular mechanisms of plant mitochondrial mRNA degradation.
- To characterize the polyadenylation and degradation processes of potato atp9 mRNAs.
Main Methods:
- Analysis of polyadenylation sites on potato atp9 mRNAs.
- In vitro degradation assays using RNA substrates with varying poly(A) tail lengths.
- Investigating the effect of non-adenosine nucleotides and secondary structures on exoribonuclease activity.
Main Results:
- The majority of potato atp9 mRNA polyadenylation sites are near the 3' end.
- A 3' to 5' exoribonuclease activity preferentially degrades polyadenylated mRNAs.
- Optimal degradation occurs with poly(A) tails of 20-30 adenosine residues.
- As few as seven non-adenosine nucleotides at the 3' end inhibit degradation.
- Exoribonuclease activity is not hindered by stable RNA secondary structures.
Conclusions:
- Polyadenylation of plant mitochondrial mRNAs promotes their degradation via a 3' to 5' exoribonuclease pathway.
- The size of the poly(A) tail is critical for efficient degradation.
- The presence of non-adenosine nucleotides or secondary structures can impede this degradation process.
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