Can the import of mRNA into chloroplasts be mediated by a secondary structure of a small non-coding RNA?
The import of diverse nucleus-encoded proteins into chloroplasts is crucial for plant life. Although this crosstalk is mainly dependent on specific transit peptides, it has been recently reported that a non protein-coding RNA (ncRNA) based on a viroid-derived sequence (vdRNA) and acting as a 5´UTR-end mediates the functional import of GFP-mRNA into chloroplasts. This observation unearths a novel plant cell signaling pathway able to control the accumulation of the nuclear-encoded proteins in this organelle. The mechanisms regulating this chloroplast-specific localization remain yet unclear. To unravel the functional nature of this chloroplastic signal, here we dissect the 5´UTR-end responsible for the chloroplast targeting. A confocal microscopy analysis in Nicotiana benthamiana leaves of the transcripts expression carrying partial deletions of the 5`UTR-end indicate that an internal 110 nucleotides-length fragment is sufficient to mediate the traffic of functional GFP-mRNA into chloroplasts. However, the capability of this motif to act as a chloroplastic localization signal was enhanced when fused to either the 5` or the 3`region of the vd-5´UTR sequence. These findings suggest that the chloroplast-specific RNA targeting is dependent on a structural motif rather than on the RNA sequence.
Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas (CSIC), Universidad Politécnica de Valencia (UPV), Valencia, Spain.
Gustavo
G
Gómez
Vicente
V
Pallás
D002736:Chloroplasts / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D049452:Green Fluorescent Proteins; D018613:Microscopy, Confocal; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D058727:RNA, Small Untranslated / Q000378:metabolism*; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism
D012333:RNA, Messenger; D058727:RNA, Small Untranslated; D049452:Green Fluorescent Proteins