Plant 24-nt reproductive phasiRNAs from intramolecular duplex mRNAs in diverse monocots
Atul Kakrana1,2, Sandra M Mathioni3, Kun Huang2
1Center for Bioinformatics and Computational Biology, University of Delaware, Newark, Delaware 19714, USA.
Genome Research
|July 14, 2018
Summary
Reproductive phased small interfering RNAs (phasiRNAs) found in grasses also exist in non-grass monocots, originating over 117 million years ago. These phasiRNAs may function in both male and female reproductive development.
Area of Science:
- Plant molecular biology
- Epigenetics
- Evolutionary biology
Background:
- Grasses possess unique 21-nt and 24-nt phased small interfering RNAs (phasiRNAs) in anthers, crucial for male reproduction.
- These phasiRNAs are analogous to piwi-interacting RNAs (piRNAs) in mammals, but their function and evolutionary history are unclear.
- The 24-nt meiotic phasiRNA pathway in grasses relies on a specific Dicer enzyme (DCL5).
Purpose of the Study:
- To investigate the evolutionary origins and mechanisms of reproductive phasiRNA pathways in non-grass monocots.
- To determine if the 24-nt meiotic phasiRNA pathway is conserved beyond grasses.
- To explore the potential roles of phasiRNAs in both male and female reproductive development.
Main Methods:
- Comparative analysis of phasiRNA pathways in garden asparagus, daylily, and lily.
- Identification and characterization of phasiRNA precursors and biogenesis pathways.
- Examination of phasiRNA presence and localization in both male and female reproductive organs.
Main Results:
- Premeiotic 21-nt and meiotic 24-nt phasiRNAs are abundant in asparagus, daylily, and lily, with similar temporal and spatial patterns as in grasses.
- The miR2275-triggered pathway producing 24-nt phasiRNAs predates the divergence of these species (over 117 million years ago).
- Distinct mechanisms for 24-nt phasiRNA production were observed, including derivation from inverted repeats in asparagus and foldback structures in lily.
- Reproductive phasiRNAs were detected in female reproductive organs, suggesting a conserved role.
Conclusions:
- The reproductive phasiRNA pathway, including the 24-nt meiotic subset, is ancient and conserved across diverse monocots.
- Multiple distinct mechanisms contribute to the production of 24-nt meiotic phasiRNAs.
- Reproductive phasiRNAs likely play roles in both male and female reproductive development, offering new insights into their evolution.
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