HASTY, the Arabidopsis EXPORTIN5 ortholog, regulates cell-to-cell and vascular microRNA movement
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Date
2021-08-02
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Journal Article
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Abstract
Plant microRNAs (miRNAs) guide cytosolic post-transcriptional gene silencing of sequence-complementary transcripts within the producing cells, as well as in distant cells and tissues. Here, we used an artificial miRNA-based system (amiRSUL) in Arabidopsis thaliana to explore the still elusive mechanisms of inter-cellular miRNA movement via forward genetics. This screen identified many mutant alleles of HASTY (HST), the ortholog of mammalian EXPORTIN5 (XPO5) with a recently reported role in miRNA biogenesis in Arabidopsis. In both epidermis-peeling and grafting assays, amiRSUL levels were reduced much more substantially in miRNA-recipient tissues than in silencing-emitting tissues. We ascribe this effect to HST controlling cell-to-cell and phloem-mediated movement of the processed amiRSUL, in addition to regulating its biogenesis. While HST is not required for the movement of free GFP or siRNAs, its cell-autonomous expression in amiRSUL-emitting tissues suffices to restore amiRSUL movement independently of its nucleo-cytosolic shuttling activity. By contrast, HST is dispensable for the movement and activity of amiRSUL within recipient tissues. Finally, HST enables movement of endogenous miRNAs that display mostly unaltered steady-state levels in hst mutant tissues. We discuss a role for HST as a hitherto unrecognized regulator of miRNA movement in relation to its recently assigned nuclear function at the nexus of MIRNA transcription and miRNA processing.
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published
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Journal / series
Volume
40 (15)
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Publisher
EMBO Press
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Subject
Arabidopsis; Argonaute; HASTY; miRNA; Movement
Organisational unit
03876 - Voinnet, Olivier / Voinnet, Olivier
03970 - De Moraes, Consuelo / De Moraes, Consuelo
Notes
Funding
323071 - High resolution and chemical genetic approaches to RNA silencing mechanisms (EC)