A Genetic Network for Systemic RNA Silencing in Plants

Area of Science:

• Plant molecular biology
• RNA silencing mechanisms
• Gene regulation

Background:

• Non-cell autonomous RNA silencing facilitates cell-to-cell and long-distance communication in plants.
• The genetic factors and signaling molecules governing mobile gene silencing in plants remain incompletely understood.

Purpose of the Study:

• To elucidate the genetic requirements for the systemic spread of posttranscriptional gene silencing (PTGS) in *Nicotiana benthamiana*.
• To identify the specific roles of DICER-LIKE (DCL) proteins in mobile RNA silencing.

Main Methods:

• Utilized transgenic RNA interference (RNAi) lines targeting DCL proteins in *Nicotiana benthamiana*.
• Employed a GFP reporter system to monitor PTGS.
• Conducted grafting experiments to differentiate signaling and response roles.

Main Results:

• DICER-LIKE2 (DCL2) is essential for the systemic spread of PTGS, with its inhibition reducing silencing.
• Suppression of DCL3 or DCL4 enhanced systemic PTGS, indicating an attenuating role.
• DCL2 is required in the scion for responding to the silencing signal, not for signal production/transmission.

Conclusions:

• A coordinated DCL genetic pathway regulates systemic PTGS in *Nicotiana benthamiana*.
• DCL2 plays a critical role in mediating the spread of PTGS.
• DCL3 and DCL4 act as negative regulators of systemic PTGS, potentially through the production of specific small interfering RNAs (siRNAs).