RETRACTED: Small RNA duplexes function as mobile silencing signals between plant cells

Area of Science:

• Plant molecular biology
• Gene silencing mechanisms
• RNA interference pathway

Background:

• The plant RNA interference (RNAi) pathway utilizes small interfering RNAs (siRNAs) processed by Dicer-like 4 (DCL4) to silence target RNAs via Argonaute 1 (AGO1).
• RNAi in plants is known to be non-cell-autonomous, but the identity of the mobile signal has remained elusive.

Purpose of the Study:

• To genetically determine the nature of the mobile silencing signal in the plant RNA interference pathway.
• To investigate whether siRNAs or their precursors constitute the mobile signal responsible for cell-to-cell RNAi spread.

Main Methods:

• Utilized cell-specific rescue of DCL4 function to assess siRNA mobility.
• Employed cell-specific inhibition of RNAi movement to block signal transmission.
• Physically tracked mechanically delivered, labeled siRNA duplexes to observe their movement and function.

Main Results:

• Established that exogenous and endogenous siRNAs, rather than precursor molecules, function as mobile silencing signals between plant cells.
• Demonstrated the physical translocation of labeled siRNA duplexes, which mimicked the spread of transgenic RNAi.
• Provided evidence suggesting that cell-to-cell movement involves siRNA duplexes, not single-stranded siRNAs bound to AGO1.

Conclusions:

• siRNAs are the mobile signals mediating non-cell-autonomous RNA interference in plants.
• The mobile silencing signal is likely in the form of siRNA duplexes, facilitating systemic gene silencing.
• This finding clarifies a fundamental aspect of RNAi pathway communication in plants.